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AD-A058 903 NATIONAL AVIATION FACILITIES EXPERIMENTAL CENTER ATL— ETC F/G 20/14
INTERFERENCE IN COMMUNICATIONS ANO NAVIGATION AVIONICS FROM COM— ETC(U)
JUN 78 EM SAWTELLE' J G DONG
UNCLASSIFIED FAA-NA-77-44 FAA-RD-78-35 NL
ODO FILE COPY AO AO 58 9 0 3
•apart Ni. FAA-RD-78-35 .
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; v. : ' V'T
INTERFERENCE IN COMMUNICATIONS AND NAVIGATION
AVIONICS FROM COMMERCIAL FM STATIONS
Edward M. Sawtelle
lames 6. Don;
D D C
SEP 18 1978
\i [s4
T’ cr
JULY 1978
FINAL REPORT
Document is available to the U.S. public through
the National Technical Information Service,
Springfield, Virginia 22161.
Prepared for
U.S. DEPARTMENT OF TRANSPORTATION
FEDERAL AVIATION ADMMISTRATKM
Systems Research i Development Service
Washington, D.C. 20590
*
(
NOTICE
The United States Government does not endorse products
or manufacturers. Trade or manufacturer's names appear
herein solely because they are considered essential to
the object of this report.
Technical Report Documentation Page
2. Government Accession No.
JNTERFERENCE IN COMMUNICATIONS AND NAVIGATION
VIONICS FROM COMMERCIAL FM STATIONS .,
* =~ *
/
7. ^ACthor^s^ — " —
i 10 [Edward M./Sawtelle
ng Organization Na
"fame and Address
James G
3. Recipient's Cotolog No.
5. Repor|^OWT»v
C/J I Ju
78
L
6. P erformTTty^O rgon^otionCfiiif
rgonizotion fljAM • Nee* -
Federal Aviation Administration
National Aviation Facilities Experimental Center
Atlantic City, New Jersey 08405
12. Sponsoring Agency Nome ond Address
U.S. Department of Transportation
Federal Aviation Administration
Systems Research and Development Service
Washington, D.C. 20590
8. Performing Orgoni zotion~1fr
FAA-NA-77-44
Work Unit No. (TRAIS)
njm
11. Contract or Grant No.
213-062-510
13. T ypejjjReport and Period Covered
Final r
jpec— R— 7 6-Novi
i ng Ag.ncy Coda
SRDS , ARD-60
15. Supplementary Notes
This project was performed by NAFEC for the Plans, Policy, and Allocation Branch of
the Spectrum Management Staff to support the Frequency Management Staff in
ngineering interference-free assignments.
1^ Abstroct
The effects of commercial frequency modulation (FM) broadcast stations on communi-
cations and navigation avionics were investigated employing several classes of
avionics receivers. Flight tests were completed employing site frequencies with
intermodulation interference determined by a computer program culling for possible
intermodulation products in selected midwestern and southern states. Laboratory
measurements were accomplished on the receivers and antenna pattern measurements of
typical aircraft antennas were obtained to determine the areas that improvements can
best be applied to alleviate the FM interference problem. Results indicate that a
10 dB increase in rejection of FM signals in avionic receivers would eliminate most
FM interferences. Included is a proposed method utilizing the Venn diagram
approach for predicting possible FM interference assignments under consideration.
It is recommended that a flight test program be established to determine FM spectrum
signatures and power levels at airports.
17. Kay Words
FM Broadcast Interference
Airborne Receivers and Antennas
Intermodulation Interference
Interference Prediction
18. Distribution Statement
Document is available to the public
through the National Technical Information
Service, Springfield, Virginia 22161
19. Security Clossif. (of this report)
Unclassified
20. Security Clossif. (of this poge)
Unclassified
21. No. of Poges
275
22. P.ic.
Form DOT F 1700.7 (8 -72)
Reproduction of completed pogo outhoriigd
FEDERAL AVIATION ADMINISTRATION
SYSTEMS RESEARCH AND DEVELOPMENT SERVICE
SPECTRUM MANAGEMENT STAFF
STATEMENT OF MISSION
The mission of the Spectrum Management Staff is to assist the
Department of State, National Telecommunications and Informa-
tion Administration, and the Federal Communications Commission
in assuring the FAA s and the nation's aviation interests with
sufficient protected electromagnetic telecommunications
resources throughout the world and to provide for the safe
conduct of aeronautical flight by fostering effective and
efficient use of a natural resource - the electromagnetic radio
frequency spectrum.
This objective is achieved through the following services:
. Planning and defending the acquisition and retention of
sufficient radio frequency spectrum to support the aero-
nautical interests of the nation, at home and abroad,
and spectrum standardization for the world's aviation
community .
. Providing research, analysis, engineering, and evalua-
tion in the development of spectrum related policy,
planning, standards, criteria, measurement equipment,
and measurement techniques.
. Conducting electromagnetic compatibility analyses to
determine intra/intersystem viability and design para-
meters, to assure certification of adequate spectrum
to support system operational use and projected growth
patterns, to defend aeronautical services spectrum
from encroachment by others, and to provide for the
efficient use of the aeronautical spectrum.
. Developing automated frequency selection computer
programs/routines to provide frequency planning,
frequency assignment, and spectrum analysis capabili-
ties in the spectrum supporting the National Airspace
System.
. Providing spectrum management consultation, assistance,
and guidance to all aviation interests, users, and pro-
viders of equipment and services, both national and
international .
TABLE OF CONTENTS
Page
INTRODUCTION 1
Purpose 1
Background 1
Description of Test Facilities and Equipment Configuration 1
DISCUSSION 2
Test Procedures and Results 2
General 2
Antenna Tests 2
Flight Tests 3
Summary of Audio Interferences 8
Receiver Tests 10
CDI and Flag Response From FM Signals Into NAV Receiver 20
Prediction of Interference 25
LIST OF ILLUSTRATIONS
Figure Page
1 Antenna Test Range 31
2 Transmitter Site 32
3 Receiver Site 33
4 Aircraft Antennas (Collins Radio) 34
5 Aircraft Antennas (General Aviation) 35
6 Antennas Employed in Flight Test 36
7 Interference Monitoring Equipment 37
8 Interference Test Receivers 38
9 Standard Flight Inspection Consoles 39
10 Receiver Configuration in Convair 580 Aircraft 40
11 Laboratory Test Configuration 41
12 Frequency Response of Navigation Aircraft Antennas 41
(General Aviation)
13 Frequency Response of Navigation Aircraft Antennas 42
(Commercial)
14 Frequency Response of Communication Aircraft Antennas 42
(Commercial)
15 Horizontal Pattern of NARCO VRP-15 Antenna 99 MHz 43
Horizontally Polarized Source
16 Horizontal Pattern of NARCO VRP-15 Antenna 110 MHz 44
Horizontally Polarized Source
17 Horizontal Pattern of NARCO VRP-15 Antenna 320 MHz 45
Horizontally Polarized Source
18 Horizontal Pattern of Collins 37R-2U Antenna 100 MHz 46
Vertically Polarized Source
19 Horizontal Pattern of Collins 37R-2U Antenna 120 MHz 47
Vertically Polarized Source
iv
LIST OF ILLUSTRATIONS (Continued)
■P
Figure Page
20
Horizontal Pattern of Collins 37R-2U
Vertically Polarized Source
Antenna
320 MHz
48
21
Horizontal Pattern of Collins 137X-1
Horizontally Polarized Source
Antenna
99 MHz
49
22
Horizontal Pattern of Collins 137X-1
Horizontally Polarized Source
Antenna
110 MHz
50
23
Horizontal Pattern of Collins 137X-1
Horizontally Polarized Source
Antenna
320 MHz
51
24
Indianapolis-Weir Cook Frame 1
52
25
Indianapolis-Weir Cook Frame 2
53
26
Indianapolis-Weir Cook Frame 3
54
27
Indianapolis-Weir Cook Frame 4
55
28
Indianapolis-Weir Cook Frame 5
56
29
Indianapolis-Weir Cook Frame 6
57
30
Indianapolis-Weir Cook Frame 7
58
31
Indianapolis-Weir Cook Frame 8
59
32
Indianapolis-Weir Cook Frame 9
60
33
Indianapolis-Weir Cook Frame 10
61
34
Kansas City-Fairfax Frame 1
62
35
Kansas City-Fairfax Frame 2
63
36
Kansas City-Fairfax Frame 3
64
37
Kansas City-Fairfax Frame 4
65
38
Kansas City-Fairfax Frame 5
66
39
Kansas City-Fairfax Frame 6
67
40
Kansas City-Fairfax Frame 7
68
v
LIST OF ILLUSTRATIONS (Continued)
Figure
41 Kansas City-Fairfax Frame 8
42 Kansas City-Fairfax Frame 9
43 Kansas City-Fairfax Frame 10
44 Kansas City-Fairfax Frame 11
45 Kansas City-Fairfax Frame 12
46 Kansas City-Fairfax Frame 13
47
Topeka-Philip
Billard
Frame
1
48
Topeka-Philip
Billard
Frame
2
49
Topeka-Philip
Billard
Frame
3
50
Topeka-Philip
Billard
Frame
4
51
Topeka-Philip
Billard
Frame
5
52
Topeka-Philip
Billard
Frame
6
53
Topeka-Philip
Billard
Frame
7
54
Topeka-Philip
Billard
Frame
8
55
Topeka-Philip
Billard
Frame
9
56
Topeka-Philip
Billard
Frame
10
57
Topeka-Philip
Billard
Frame
11
58
Topeka-Philip
Billard
Frame
12
59 Denver-Jef ferson County Frame 1
60 Denver-Jef ferson County Frame 2
61 Denver-Jefferson County Frame 3
62 Denver-Jefferson County Frame 4
63 Denver-Jefferson County Frame 5
vi
Page
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
-
r
LIST OF ILLUSTRATIONS (Continued)
Figure Page
64
Denver- Jefferson
County
Frame
6
92
65
Denver- Jefferson
County
Frame
7
93
66
Denver-Jefferson
County
Frame
8
94
67
Denver-Jef f erson
County
Frame
9
95
68
Denver-Jefferson
County
Frame
10
96
69
Denver-Jefferson
County
Frame
11
97
70
Denver-Jefferson
County
Frame
12
98
71
Denver-Jefferson
County
Frame
13
99
72
Denver-Jefferson
County
Frame
14
100
73
Denver-Jefferson
County
Frame
15
101
74
Denver-Jefferson
County
Frame
I 6
102
75
Albuquerque- International
Frame
1
103
76
Albuquerque- International
Frame
2
104
77
Albuquerque- International
Frame
3
105
78
Albuquerque- International
Frame
4
106
79
Albuquerque- International
Frame
5
107
80
Albuquerque- International
Frame
6
108
81
Albuquerque- International
Frame
7
109
82
Albuquerque- In ter national
Frame
8
110
83
Albuquerque- Inter national
Frame
9
111
84
Albuquerque- International
Frame
10
112
85
Albuquerque-International
Frame
11
113
86
Albuquerque- International
Frame
12
114
vii
LIST OF ILLUSTRATIONS (Continued)
Figure Page
87 San Antonio-International Frame 1 115
88 San Antonio-International Frame 2 116
89 San Antonio-International Frame 3 117
90 San Antonio-International Frame 4 118
91 San Antonio-International Frame 5 119
92 San Antonio-International Frame 6 120
93 San Antonio-International Frame 7 121
94 San Antonio-International Frame 8 122
95 San Antonio-International Frame 9 123
96 San Antonio-International Frame 10 124
97 San Antonio-International Frame 11 125
98 San Antonio-International Frame 12 126
99 San Antonio- International Frame 13 127
100 San Antonio-International Frame 14 128
101 San Antonio- International Frame 15 129
102 San Antonio-International Frame 16 130
103 Houston-Hobby Field Frame 1 131
104 Houston-Hobby Field Frame 2 132
105 Houston-Hobby Field Frame 3 133
106 Houston-Hobby Field Frame 4 134
107 Houston-Hobby Field Frams 5 135
108 Houston-Hobby Field Frame 6 136
viii
LIST OF ILLUSTRATIONS (Continued)
Figure Page
109 Houston-Hobby Field Frame 7 137
110 Houston-Hobby Field Frame 8 138
111 Houston-Hobby Field Frame 9 139
112 Houston-Hobby Field Frame 10 140
113 Houston-Hobby Field Frame 11 141
114 Dallas-Love Field Frame 1 142
115 Dallas-Love Field Frame 2 143
116 Dallas-Love Field Frame 3 144
117 Dallas-Love Field Frame 4 145
118 Dallas-Love Field Frame 5 146
119 Dallas-Love Field and Regional Ft Worth/Dallas Frame 1 147
120 Dallas-Love Field and Regional Ft Worth/Dallas Frame 2 148
121 Dallas-Love Field and Regional Ft Worth/Dallas Frame 3 149
122 Dallas-Love Field and Regional Ft Worth/Dallas Frame 4 150
123 Dallas-Love Field and Regional Ft Worth/Dallas Frame 5 151
124 Dallas-Love Field and Regional Ft Worth/Dallas Frame 6 152
125 Dallas-Love Field and Regional Ft Worth/Dallas Frame 7 153
126 Dallas-Love Field and Regional Ft Worth/Dallas Frame 8 154
127 Dallas-Love Field and Regional Ft Worth/Dallas Frame 9 155
128 Dallas-Love Field and Regional Ft Worth/Dallas Frame 10 156
129 Dallas-Love Field and Regional Ft Worth/Dallas Frame 11 157
130 Dallas-Love Field and Regional Ft Worth/Dallas Frame 12 158
131 Dallas-Love Field and Regional Ft Worth/Dallas Frame 13 159
ix
LIST OF ILLUSTRATIONS (Continued)
Figure
Page
132
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
14
160
133
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
15
161
134
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
16
162
135
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
17
163
136
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
18
164
137
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
19
165
138
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
20
166
139
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
21
167
140
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
22
16U
141
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
23
169
142
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
24
170
143
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
25
171
144
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
26
172
145
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
27
173
146
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
28
174
147
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
29
175
148
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
30
176
149
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
31
177
150
Dallas-Love
Field
and
Regional
Ft Worth/Dallas
Frame
32
178
151
FM Spectrum,
, Birmingham-Municipal, Rwy 5
179
152
FM Spectrum,
Birmingham-Municipal, ORBIT 5 nmi
180
153
Selectivity,
AM Signal 108.3 MHz Escort (NAV)
181
154
Selectivity,
1 AM
& 1
FM Signal Escort (NAV)
182
x
LIST OF ILLUSTRATIONS (Continued)
Figure
155
Selectivity,
1 AM & 2
FM Signals, Test 2
Escort (NAV)
Page
183
156
Selectivity ,
1 AM & 2
FM Signals, Test 4
Escort (NAV)
184
157
Selectivity,
1 AM & 2
FM Signals, Test 5
Escort (NAV)
185
158
Selectivity,
1 AM & 2
FM Signals, Test 6
Escort (NAV)
186
159
Selectivity,
1 AM & 2
FM Signals, Test 7
Escort (NAV)
187
160
Selectivity,
1 AM & 2
FM Signals, Test 2
Escort (COM)
188
161
Selectivity,
1 AM & 2
FM Signals, Test 3
Escort (COM)
189
162
Selectivity,
1 AM & 2
FM Signals, Test 4
Escort (COM)
190
163
Selectivity,
1 AM & 1
FM Signals, Test 2
ARC NAV 400
191
164
Selectivity,
1 AM & 2
FM Signals, Test 3
ARC NAV 400
192
165
Selectivity,
1 AM i 2
FM Signals, Test 4
ARC NAV 400
193
166
Selectivity,
1 AM & 2
FM Signals, Test 5
ARC NAV 400
194
167
Selectivity,
AM Signal 123.0 MHz King 195B
195
168
Selectivity,
AM Signal 126.25 MHz King 195B
196
169
Selectivity,
1 AM & 2
FM Signals, Test 2
King 195B
197
170
Selectivity,
Multiple
1, Distortion Test
1 King 195B
198
171
Selectivity,
Multiple
1, Distortion Test
2 King 195B
199
172
Selectivity,
Multiple
1, Distortion Test
3 King 195B
200
173
Selectivity,
Multiple
2, Distortion Test
1 King 195B
201
174
Selectivity,
Multiple
3, Distortion Test
2 King 195B
202
175
Selectivity,
Multiple
3, Distortion Test
3 King 195B
203
176
Selectivity,
AM Signal 122.8 MHz Genave 10
204
177
Selectivity,
AM & 2 FM Signals, Test 2 Genave 10
205
xi
LIST OF ILLUSTRATIONS (Continued)
Figure Page
178 Selectivity, AM & 2 FM Signals, Test 6 Genave 10 206
179 Selectivity, AM & 2 FM Signals, Test 7 Genave 10 207
180 Selectivity, Distortion Test 4 Genave 10 208
181 Selectivity, Distortion Test 5 Genave 10 209
182 Selectivity, AM & 2 FM Signals Test 4 COM 11A 210
183 Selectivity, AM & 2 FM Signals Test 5 COM 11A 211
184 Selectivity, AM & 2 FM Signals Test 2 EDO-AIRE 212
185 Selectivity, AM & 2 FM Signals Test 3 EDO-AIRE 213
186 Selectivity, Distortion Test 1 EDO-AIRE 214
187 AGC Response, AM & FM Signals Escort 110 215
188 Intermodulation Test 1, 2 FM Signals Escort 110 216
189 Intermodulation Test 2, 2 FM Signals Escort 110 217
190 Intermodulation Test 8, 2 FM Signals Escort 110 218
191 Intermodulation Test 2, 2 FM Signals Escort 110 219
192 Intermodulation Test 1, 2 FM Signals Escort 110 (COM) 220
193 Intermodulation Test 5, 2 FM Signals Escort 110 (COM) 221
194 AGC Response, AM & FM Signals Mark 12 222
195 Intermodulation Test 1, 2 FM Signals Mark 12 223
196 Intermodulation Test 2, 2 FM Signals Mark 12 224
197 Intermodulation Test 3, 2 FM Signals Mark 12 225
198 Intermodulation Test 4, 2 FM Signals Mark 12 226
199 AGC Response, AM & FM Signals Genave, EDO-AIRE 227
200 Intermodulation Test 1, 3 FM Signals Genave 228
xii
LIST OF ILLUSTRATIONS (Continued)
Figure
Page
201
Intermodulation
Test
12, 2 FM Signals Genave
229
202
Intermodular ion
Test
13, 2 FM Signals Genave
230
203
Intermodulation
Test
4, 3 FM Signals EDO-AIRE
231
204
AGC Response, AM & FM Signals NAV 400
232
205
Intermodulation
Test
1, 2 FM Signals NAV 400
233
206
Intermodulation
Test
3, 2 FM Signals NAV 400
234
207
Intermodulation
Test
6, 2 FM Signals NAV 400
235
208
Intermodulation
Test
7, 2 FM Signals NAV 400
236
209
AGC Response, AM & FM Signals King 195B
237
210
Intermodulation
Test
1C, 2 FM Signals King 195B
238
211
Intermodulation
Test
ID, 2 FM Signals King 195B
239
212
Intermodulation
Test
3C, 2 FM Signals King 195B
240
213
Intermodulation
Test
2, 2 FM Signals King 195B
241
214
Intermodulation
Test
3, 2 FM Signals King 195B
242
215
Intermodulation
Test
4, 2 FM Signals King 195B
243
216
Intermodulation
Test
5, 2 FM Signals King 195B
244
217
Intermodulation
Test
6, 2 FM Signals King 195B
245
218
Intermodulation
Test
11, 2 FM Signals King 195B
246
219
Intermodulation
Test
2, 3 FM Signals King 195B
247
220
Intermodulation
Test
3, 3 FM Signals King 195B, Escort 110
249
221
ILS and FM Intermodulation to COM Rec.
251
222
AGC RESPONSE, AM 6. FM SIGNALS COM 11A
252
223
INTERMODULATION
TEST
, ELT/REC SEPARATION CHANGE, KING 195B
253
LIST OF ILLUSTRATIONS (Continued)
Figure Page
224 Intermodulation Test 7, 2 FM Signals COM 11A 254
225 Intermodulation Test 8, 2 FM Signals COM 11A 255
226 Intermodulation Test 9, 2 FM Signals COM 11A 256
227 Intermodulation Test 10, 2 FM Signals COM 11A 257
228 AGC Response, AM & FM Signals Bendix 258
229 Receiver Signal Level Diagram for PRDCOM and PRDNAV 259
230 Two FM Station Interference Areas for PR = -10 and 260
PR = -30
231 Two FM Station Interference Areas for PR = -20 261
232 Topeka, Kansas FM Station Radiation Power Circles 262
xiv
LIST OF TABLES
Table Page
1 Audio Interference in Communication Receivers 9
2 Summary of Audio Interferences 10
3 Distortion Test, Genave 12
4 Distortion Test, King 195B, 3 FM Signals 13
5 Distortion Test 3, EDO-AIRE 13
6 Distortion Test 4, EDO-AIRE 14
7 Distortion Test, King 195B, 2 FM Signals 14
8 Intermodulation Test 1, Mark 12, CDI Deflection 21
9 Intermodulation Test 2, Mark 12, CDI Deflection 21
10 Intermodulation Test 3, Mark 12, CDI Deflection 22
11 Intermodulation Test 4, Mark 12 and Ben dix CDI Deflection 23
12 Intermodulation Test 5, Mark 12 and Bendix CDI Deflection 23
13 Intermodulation Test 6, Mark 12 and Bendix CDI Deflection 24
14 Intermodulation Test, NAV 400 CDI Deflection 24
15 Expected Power Levels for Selected Coefficient 26
Combinations of Intermodulation Equation
xv
INTRODUCTION
PURPOSE.
The purpose of this project was to determine distance/frequency separation
criteria required between communication and navigation avionics and high-
powered frequency modulated (FM) commercial stations operating in common
geography.
BACKGROUND.
An increasing number of applications are being submitted to the Federal
Communication Commission (FCC) for FM broadcast power increases. Federal
Aviation Administration (FAA) frequency management has been opposing these
when proximity to runway approaches or other low-altitude routing would expose
aircraft with very high frequency (VHF) navigation communication NAV/COM
avionics to extraneous power levels capable of causing third order intermodu-
lation or other "brute force" spurious interference.
Distance criteria is necessary to limit FM signals to tolerable signal levels.
Frequency planning details are required to avoid intermodulation or other
spurious interference. The information is for use by frequency management
engineers and is suitable to provide FAA technical support for enclosure
with comments to FCC on license applications.
DESCRIPTION OF TEST FACILITIES AND EQUIPMENT CONFIGURATION.
The three primary test facilities employed in accomplishing this effort were
the National Aviation Facilities Experimental Center's (NAFEC): antenna test
range, Convair 580 aircraft, (N-49), and a laboratory screen room.
The antenna test range at NAFEC (figure 1) is situated where the transmitter
site and receiver site are separated by a fresh water reservoir. At the
transmitter site (figure 2), the source antenna is a log periodic type. Scien-
tific Atlanta series 26. Equipment for illuminating the antenna is installed
in a mobile trailer and the alternate current (a.c.) power is supplied by
a standby-type power plant.
At the receiver site (figure 3) the antenna under test was mounted on a
curved metal sheet to simulate an aircraft fuselage providing a ground plane
for the antenna. A Scientific Atlanta model 1640 CW receiving system with a
sensitivity of -95 decibels per milliwatt (dBm) and a model 1530 polar plotter
were employed at the site. Antennas tested on the range are shown in
figures 4 and 5. In figure 4, the Collins antennas are representative of
antennas commonly employed on air carriers. The type 37J-3 is a navigation
(VOR and localizer) antenna and the type 37-R2/2U is a VHF communication
antenna. The type 137X-1 antenna is a combined unit applicable for communi-
cation and/or navigation use. The antenna types A-13B and VRP-15 (figure 5)
are of lower quality and used by small general aviation type aircraft.
1
The Convair 580 aircraft and the antennas employed in the receiver tests are
shown in figure 6. Omitted in this figure is an emergency locator transmitter
(ELT) antenna which is located 2 feet (0.61 meter (m)) in front of the rear
137X-1 antenna atop the aircraft. Monitoring equipment and test receivers
were connected to the aircraft antennas through radiofrequency (rf) power
splitters as shown in figure 7 and 8 respectively. The monitoring equipment
(figure 7) included a COM 11A receiver, spectrum analyzer, and a 8-channel
strip chart recorder. The strip recorder was used to record course deviation
indicator (CDI) and automatic gain control (AGC) outputs of test receivers
shown in figure 8. Full scale deflection left and right of center for the CDI
was adjusted to 25 microamperes (pA) on the recorder. The AGC recordings for
each receiver were scaled from zero signal AGC to maximum AGC.
The CDI was recorded for the following receivers: Bendix FA-4165-3A, Escort 110,
Mark 12, and NAV 400. On the four remaining channels, the AGC was recorded on
the following receivers: COM 11A, KY195B, Bendix FA-4165-3A, and Mark 12. The
audio outputs of all receivers was recorded by the 14-channel recorder
(figure 8).
The time code generator supplied the real time to the 14-channel recorder
enabling time correlation with the flight inspection consoles shown in
figure 9. The Dome and Margolin DM-N-4 antenna was employed with the flight
inspection consoles. Details depicting the use of other aircraft antennas
with the test receivers are shown in figure 10. A laboratory screen room was
employed to simulate with test equipment the effects of strong FM signals on
avionic receivers to corroborate recorded characteristics of a live environ-
ment of FM commercial broadcast stations. Interference effects of ELT on
receivers were also measured using the configuration shown in figure 11.
DISCUSSION
TEST PROCEDURE AND RESULTS.
GENERAL. Preliminary testing was accomplished at NAFEC to obtain charteristics
of the VHF NAV/COM systems employed in aircraft and to select suitable equip-
ments to be tested in an environment of commercial FM broadcast stations.
Other considerations given in equipment selection for test included equipment
population and availability. The test results were expected to determine the
cause of present FM interference problems and develop techniques for setting
certain constraints in frequency assignments to prevent future FM interference
problems. Basic investigation of FM interference was directed towards antenna
tests, NAV/COM receivers tests in a live FM commercial broadcast environment,
and laboratory tests. Included is a suggested Venn diagram approach for pre-
dicting interference.
ANTENNA TEST. The antennas selected for test were considered representative
of those used in general/commercial aircraft. Frequency response characterstics
of the antennas were made to estimate the rf levels expected at the receiver.
2
Antenna patterns were also recorded in the horizontal plane simulating the
variations in signal level with the horizontal position of the aircraft.
Results of the frequency response measurements are shown in figures 12, 13,
and 14. Patterns of some antennas tested at different frequencies are recorded
in figures 15 through 23 exhibiting antenna response with respect to the
receiving antenna orientation to the transmitting antenna. The gain of the
reference standard antenna is 2.15 dB greater than an isotropic antenna.
Measurements were also accomplished on similar antennas mounted on the
Convair 580 aircraft. A Hewlett Packard spectrum analyzer with ancillary
modules was used as a receiver. A signal generator was used to illuminate
the dipole antenna used as a source. The source antenna was placed 15 feet
(4.5 m) from the aircraft and within the line of sight, between the two
137X-1 antennas at the rear of the aircraft. The dipole was positioned
horizontally and vertically in this plane.
With the horizontally polarized navigation antennas and the vertically
polarized communication antennas receiving orthogonal (cross-polarized)
polarized signal, the reduction of the signal of the orothogonal polarized
signal at the receiver was reduced 20 dB in the frequency range of 88 to
118 MHz. The Dome and Margolin DM N-4 antenna was not employed with the test
receivers because the received FM signal level was at least 5 dB less than
other VHF antennas on the aircraft. The increased loss was attributed to the
longer cables lengths required to reach the vertical stabilizer on the air-
craft. In addition, the DM N-4 antenna was designed to have substantially
greater discrimination against vertically polarized signals than the ramshorn-
or VEE-type antennas.
FLIGHT TESTS. Using the airborne equipment described previously, instrument
approaches and tracks were flown at the following locations: Atlantic City,
New Jersey; Indianapolis, Indiana; Kansas City and Topeka, Kansas; Denver,
Colorado; Albuquerque, New Mexico; San Antonio, Houston, Dallas, and Ft. Worth,
Texas; Birmingham, Alabama; and Opa Locka, Florida. Prior to any flight tests,
combinations of the FM frequencies being radiated by FM stations near the
selected airports were culled by a computer to determine the test receiver
frequencies to be used in flight. In addition, the NAV/COM receivers were
tuned to the respective site frequencies authorized at the sites and suspected
of having intermodulation interference resulting from commercial FM broadcoast
station. Also, the high power FM station towers were designated on the
air map to assure that the tracks flown would pass above the antennas at
minimal altitudes to receive the maximum FM signal the aircraft receivers
would encounter. The spectrum analyzer was used to record the presence of FM
signals and the dBm levels received at the aircraft.
Preliminary flight testing was accomplished at Atlantic City to establish the
FM power levels expected near the selected airports to be investigated and
also to test the operation of the data collection equipment prior to departure
to other sites with interference problems. A description of the tracks flown
at each location is included with the recorded sample of the results. In
3
each sample (frame), 30 seconds of AGC and CDI recordings for the Bendix and
Mark 12 receivers are grouped with a photograph taken within the sample period
of the spectrum analyzer tuned to the FM band. Although the photographs of
the FM band are not sharply defined, relative amplitudes and frequency separa-
tions of the radiation from FM commercial broadcast stations can be observed.
The alphanumerics of the spectrum analyzer photographs are the following in
sequence left to right; top — dBm reference level, center frequency, resolution;
bottom — display mode, frequency span per division. These spectrum photographs
were taken from display of the video tape playback. The video camera was used
in lieu of oscilloscope Polaroid® camera. The video tape continuous recording
of the spectrum allowed selection of particular samples that could not have
been followed by the Polaroid camera because of the rapid changes in the
spectrum signal amplitude during flight. The receiver's audio interference
was recorded on the 14-channel recorder and time correlated with the other
data. Most of the selected sample frames were of the Mark 12 because of the
perceptible deviations in the CDI and/or AGC in the strip chart recordings
which were indicative of interference. The specific type (i.e., motorboating,
hum, music) could not be determined from the chart recordings except as noted
for speech or music below. Using time for correlation, the audio recordings
were checked for the type of interference observed on the strip charts.
Results of the flight test at Indianapolis-Weir Cook Airport are shown in
figures 24 through 33. The track was flown at a mean sea level (MSL) altitude
of 2500 feet (762 m) along a route beginning at the Shelbyville, Indiana com-
bined VOR and TACAN system (VORTAC) thence via Victor Airway 97 to the Zippy
intersection (32 nautical miles (nmi) northwest of Shelbyville VORTAC), pro-
cedure turn, thence return to the Shelbyville VORTAC via Victor Airway 97.
From the selected frames assembled from the flights accomplished in Indiana,
only one frame indicated that no interference was present in either naviga-
tion receivers. However, in subsequent flights near the same location, inter-
■^rcnce did occur in the Mark 12 receiver. The number of frames and the
types'*?^. interference recorded from the Mark 12 receiver were: four frames
with motorboating sound, four frames of interference from music, and one frame
with heterodyning. In the AGC and CDI sampling of the Mark 12 receiver, with
music interference numerous minor variations were evident on the strip chart
recording. Also, the prime interference signal was apparent in the FM
spectrum at the required level.
Results of the flight test at Kansas City Fairfax Airport are shown in
figures 34 through 46. The track was flown at an altitude of 2500 feet
(762 m) MSL along a direct route that tracked State Highway Route 635.
This direct route was initiated at the 16 nmi distance measuring equipment (DME)
fix on the Kansas City VORTAC 116° radial, thence direct to the 14 nmi DME
fix on the Kansas City VORTAC 190° radial, procedure turn, then direct to the
initial DME fix, procedure turn, thence a second flight of the described
round-robin route.
The sample frames revealed that audio interferences were present in the
Mark 12 receiver: three with aircraft engine noise, six with motorboating
sound, three with music and/or speech, and one frame with no interference in
4
r 1
either receiver. On the 300° radial, 13 nmi from the VORTAC, high background
noise occurred in the Bendix receiver while motorboating sound was present in
the Mark 12 receiver. On the 360° radial, 13 nmi from the VORTAC with the
aircraft passing above FM antenna number (No.) 6; motorboating sound was pre-
sent in the Bendix receiver while music was present in the Mark 12 receiver.
On the 300° radial, 13 nmi from the VORTAC with the aircraft passing above
antenna No. 6; motorboating sound was present in both receivers. The wide
trace of the Mark 12 CDI in figure 37 was attributed to 30 Hertz (Hz) oscilla-
tions which occurred when the receiver was tuned to the VHF omnidirectional
radio range (VOR) frequency. Minor variations when music interference was
present occurred with larger and slower changes in the Mark 12 automatic gain
control (AGC) curve and were sometimes present in the frames with other types
of interferences detected by the receiver.
Results of the flight test at Topeka, Philip Billard Airport, are shown in
figures 47 through 58. The track was flown at an altitude of 2500 feet
(762 m) MSL from the Topeka VORTAC to the 10 nmi DME fix on the Topeka VORTAC
237° radial, thence at 3000 feet (914.4 m) MSL direct to the 24 nmi DME fix
on the Topeka VORTAC 245° radial, thence at 2000 feet (609.6 m) MSL direct to
the 6 nmi DME fix on the Topeka VORTAC 292° radial direct Topeka VORTAC, thence
a second flight of the described route. Only one frame indicated that no inter-
ference was present in either the Bendix or Mark 12 receivers. Other frames
include, eight frames with motorboating and three frames with music/speech.
When the FM spectrum analysor reference level setting was at -10 dBm (top
raster line is -10 dBm for -10 dBm setting) many of the FM stations radiation
was not visible on the analyzer. However, at an analyzer setting of -20 dBm
the radiation from the many FM stations was apparent when the video tape was
viewed in the laboratory. The level setting is the first number on the left
at the top of the photograph.
Results of the flight test at Denver, Jefferson County Airport, are shown in
figures 59 through 74. The track was flown from the Denver VORTAC direct to
the 12 nmi DME fix on the Denver VORTAC 194° radial, thence direct to the
24 nmi DME fix on the Denver VORTAC 240° radial, thence direct to the 22 nmi
DME fix on the Denver VORTAC 212° radial, thence direct to the Denver VORTAC.
The altitude parameter for this flight was specified as maintenance of 1000
feet (304.8 m) above ground level. Actual flight altitude, due to terrain
considerations, ranged from 6500 feet (1981.2 m) to 8600 feet (2621.3 m) MSL.
In the selection of some AGC and CDI samples there were two blanks in the
audio data and three in the FM spectrum because of malfunctions in the audio
and video tape recorders. Other frames included: two frames with high back-
ground noise, four frames with motorboating, and eight frames with music/
speech. It seems that the frames with blank audio data, music/speech inter-
ference were present in the Mark 12 receiver by observing the similarity of
other AGC curves when music/speech interference was present. It should be
noted that no interference was present in the Bendix receiver in any of the
frames .
5
Results of the flight test at Albuquerque International Airport are shown in
figures 75 through 86. The track flown consisted of two parts to properly
cover the FM antenna locations in the area. Part 1 was flown at an altitude
of 6300 feet (1920.3 m) MSL from the Albuquerque VORTAC to the 5 nmi DME fix
on the 062° radial of the Albuquerque VORTAC, thence direct to the 20 nmi
DME fix on the 045° radial of the Albuquerque VORTAC, procedure turn, thence
direct to the initial DME fix.
Part two was flown at an altitude of 11,500 feet (3505.2 m) MSL from the
Albuquerque VORTAC to the 20 nmi DME fix on the 45° radial of the Albuquerque
VORTAC, right turn to and maintain a 20 nmi arc of the Albuquerque VORTAC until
the test termination time.
In some locations, the selected frames depicting interference are not within
the prescribed tracks originally specified because of deviations imposed by
the existing air traffic. Sometimes, tracks were slightly altered to lessen
the burden on the local air traffic control or to provide better interference
coverage observed during flight.
The results obtained revealed five blank samples in the frames because of poor
positioning of the video camera. In all sample frames taken, the Mark 12
received interference, four frames with distorted voice (speech) and eight
frames with motorboating sound. The Bendix receiver motorboating interference
occurred only in one frame with the aircraft on the 062° radial and 9 miles
from the Albuquerque VORTAC.
The results of the flight test at San Antonio International Airport are shown
in figures 87 through 102. The track was flown at an altitude of 1800 feet
(548.6 m) MSL from the San Antonio VORTAC to the 20 nmi DME fix on the 121°
radial of the San Antonio VORTAC, thence direct to 12.5 nmi DME fix on the
177° radial of San Antonio VORTAC, thence direct to the San Antonio VORTAC.
No audio interferences were received by the Bendix receiver. Interferences
received by the Mark 12 receiver consisted of nine frames with motorboating
sound and seven frames with music. Music interference was received within a
mile of the outer marker on approaches and flying a track on the 158° radial
at 13 and 16 nmi from the San Antonio VORTAC.
The results of the flight test at Houston, Hobby Field are shown in figures 103
through 113. The track was flown at an altitude of 1200 feet (365.8 m) MSL
from the Houston VORTAC to the 19 nmi DME fix on the 182° radial of the
Houston VORTAC, thence direct to the 12 nmi DME fix on the 177° radial of the
Houston VORTAC, thence direct to the 12 nmi DME fix on the 170° radial of the
Houston VORTAC, thence direct to the Houston VORTAC, thence a second flight
along the described route.
No interference was received by the Bendix receiver. Interference received
by the Mark 12 receiver consisted of eight frames with motorboating sound and
three frames with music.
6
Music was received by the Mark 12 receiver at the following locations: on an
approach runway 13, 1 nmi outside of the outer marker, on the 184° radial 16 nmi
from the VORTAC, and on the 170° radial 12 nmi being over FM antenna number 3.
Approaches accomplished at Dallas, Love Field, are shown in figures 114 through
118. No interference was received by the Bendix receiver, but motorboating
was present in the Mark 12 receiver. In some frames the ACC trace with many
small rapid variations are similar to traces observed when music/speech was
present. It seems to imply that music/speech might be present but was masked
by the motorboating sound.
The track completed in Dallas, Love Field , and Regional Ft Worth/Dallas was
comprised of three parts. Part one was flown at an altitude of 1800 feet
(548.6 m) MSL from the Greater Southwest VORTAC (GSW) to the 15 nmi DME fix on
the 151° radial of GSW VORTAC, thence direct to visual check point Gears, cross
Gears at 2500 feet (762 m) , thence direct to the 12 nmi DME fix on the
217° radial of GSW VORTAC, procedure turn, thence direct to the initial DME fix.
Part two was accomplished at a MSL altitude of 4000 feet (1219.2 m) from
Scurry VORTAC direct to visual check point Gears via the 203° radial of the
Scurry VORTAC. Part three required the aircraft to be flown at an altitude
of 4000 feet (1219.2 m) MSL from the Love VORTAC direct to visual check point
Netty via the 232° radial of the Love VORTAC.
The results of the flight test in Dallas/Ft Worth are shown in figures 119
through 150. No interference was present in the Bendix receiver during the
flight test while it was evident in the Mark 12 receiver. From the 32 samples
assembled, 15 frames had interference from music, 12 frames with motorboating
sound, and 5 frames with high background noise which also includes the frames
with noise and motorboating combined.
Several months later by request, additional flight tests were accomplished in
Alabama, Birmingham Municipal Airport, and Florida, Opa Locka, using basically
the same test equipments. To obtain a better reproduction of the FM spectrum,
a motion picture camera was used in conjunction with the video camera viewing
the oscillosope presentation on a special split image mirror.
At Birmingham, instrument landing system (ILS) approaches were made. Included
in the flights were orbits of 5 nmi and a track from the Birmingham VOR direct
on the 150° radial to a distance of 15 nmi and returning to the Birmingham VOR
via the 150° radial. No rf interference was detected by the Bendix and COM
11A receivers during the flight. Hum and motorboating sounds were apparent
in the King 195B, Mark 12, Escort 110, NAV 400, and Genave 100 receivers.
In addition, during one of the approaches and one of the 5 nmi orbits, inter-
vals of music/speech-type of interference were detected by these receivers.
While on one of the ILS approaches, the ILS transmitter was reduced 12 dB
from the normal 180 watts output to determine its effect on interference.
Subsequent approaches with full transmitter power indicated no effect from
reduction of ILS transmitter power on FM interference. Figure 151 shows
the variations in FM spectrum for a brief period time during an ILS approach
when music/speech interference was present, and figure 152 shows the FM spectrum
changes for short time during the 5 nmi orbit when music/speech interference
was present. It was observed during this flight test that the FM spectrum
changed slower than spectrum changes at other locations. Consequently, it is
suspected that the rate of change in the FM spectrum during a flight is
related to the number and location FM stations relative to the aircraft and
peculiarities in the ground environment. To improve the correlation of the
FM spectrum with rf interference, a digital data collection system is being
considered for purchase which will allow better reproduction of the spectrum
from the digital tape recording and permit signal processing to be executed
on the spectrum with the associated computer and compared with receiver
parameters and aircraft position.
At Opa Locka Airport, ILS approaches made on runways 9L and back course 27R
caused no interference in the Bendix and COM 11A receivers. Hum and motor-
boating sounds occurred in the King 195B, Mark 12, and NAV 400 receivers dur-
ing the four ILS approaches on runway 9L, two VOR approaches on runway 9L, and
four ILS approaches on runway 27R. Intermittent receiver noise bursts occurred
on the Escort 110 during one ILS approach on runway 27R. The ILS approach
frequency was 110.5 MHz. Music/speech interference was detected by the
Genave 100 receiver tuned to 120.7 MHz during an ILS approach on runway 9L and
two ILS approaches on runway 27R with the receiver tuned to 121.9 MHz.
A request was made by the air traffic controller to check 120.7 MHz for rf
interference on the ground. During the ground check, there was heterodyning
(high pitch whistle) in the audio of the COM 11A receiver, but desired speech
would override the interference. In the Genave 100 receiver, intermittent
burst of music/speech occurred at the end of runway 9 taxiway.
Since the Mark 12 and Bendix receivers were used to give a comparison of the
rf interference effects on navigational receivers, table 1 shows the effects
of interference on communication receivers. The communication receivers were
not as susceptible to FM interference compared to navigational receivers;
therefore, only the results obtained at Topeka are depicted as an example of
airborne communication receivers behavior in FM interference environment. As
listed in the table 1, the Genave 100 receiver was the most susceptible to
the interference. This receiver is a low-cost, general-aviation type receiver.
The effects of the Share 7 ELT had no effect on the amount of interference
because the FM signal was not sufficient in magnitude. In the N49 aircraft
there was also a Narco ELT 10 which is the regular unit installed in the air-
craft, but this ELT antenna located near the tail was too distant from other
antennas to have effect.
SUMMARY OF AUDIO INTERFERENCES. A listing of audio interference is found in
table 2. The most prevalent types of interference occurring in the Mark 12
receiver were motorboating sound and music/speech. The aircraft noise, which
sounds like a single engine aircraft, may be considered a variation of the
motorboating sound. The motorboating sound could vary in pitch, level of
loudness, and frequency of bursts. Music/speech type of interference may be
clearly audible or sometimes distorted. The high background music may be
similar to a high level of receiver noise or may include high level hum. The
8
heterodyning noise may sound like a high pitch whistle and only occurred in
one of the frames. These interferences were evident in the Mark 12 receiver
which is considered a general-aviation type navigational receiver. In the
Bendix high quality receivers, the only location that interference was
evident in this receiver was at Kansas City, Fairfax Airport, where three of
the sample frames showed high background noise.
TABLE 1. AUDIO INTERFERENCE IN COMMUNICATION RECEIVERS
Flight Action
1. ILS Runway l l
2. ILS Runway 13
3, ILS Runway 1 1
4. ILS Runway 13
5. BC Runway 31
b. BC Runway 31
. ropeka VQR
2 37°R/10 3*—
245°R/24 ft-#
292°R/6
8. Reverse of Flight
At t ion 7
COM 1 1 A
121.7 MHz No Interference
121.9 MHz No Interference
118.7 MHz Starting at
5.5 nmi Garbled Speech
4 st i tiu rat ion
11*9.7 MHz No Interference
121.9 MHz No Interference
121.9 MHz No Interference
121.9 MHz No Interference
121.9 Mllz No Interference
King 195B
1 21.7 MHz No Interference
121.9 MHz Starting at 7 nmi
Heterodyning and Motor-
boating 37 see duration
118.7 MHz No Interference
118.7 MH i No Interference
121.9 MHz Starting at 7 and
5.5 nmi Garbled Speech 1 and
5 sec duration
121.9 MHz Starting at 7 nmi
Heterodyning
121.9 MHz No Interference
121.9 MHz No Interference
Genave 100
118.7 MHz Continuous
Motorboating Sound
118.7 MHz Starting at
8 nmi Noise 8 sec dura-
t ion; at 4 nmi Music
b sec duration
121.7 MHz Starting at
7 nmi Garbled Speech
3 sec duration and at
5.5 nmi Music 1 1/2 min
durat ion
121.7 MHz Starting at 7 nmi
Garbled Speech 3 sec dura-
tion at 5.5 nmi Heterodyning
3 (8 sec bursts)
118.7 MHz continuous Motor-
boat ing sound
118.7 MHz continuous Motor-
boat ing sound
118.7 MHz Starting at 7 nmi
Music 25 sec duration 20 to
23 nmi Music 3 (5 sec bursts
118.7 MHz Starting at 9 nmi
Music 25 sec duration out-
bound near KTOP
9
TABLE 2.
SUMMARY OF AUDIO INTERFERENCES
Number of Occurrences
Flight Test
Location
Indianapolis-Weir Cook
Aircraft
Noise
4
Background
Music /Speech Noise
4
Motorboat ing
Sound
Kansas City-Fairfax
3
b
3
Topeka-Phi 1 ip Billard
Remarks
One occurrence of
Heterodyning and one
frame with no inter-
ference
3 frames with high back-
ground noise in Bendix
receiver. One frame
with no interference
One frame with no inter-
ference
Denver-3ef ferson County
Albuquerque-Internat ional
San Antonio-lnternat ional
Houston-Hobbv Field
Dallas-Love Field
Dallas-Love Field and
Regional Ft Worth/Dallas
2
8
9
8
5
12
9
4
7
3
15
3 2 Blank recordings
RECEIVER TESTS. The objectives of these tests were to provide baseline data
on the NAV/COM receivers for selectivity and sensitivity performance at
several frequencies across the VHF band before adding the interfering inter-
modulation FM signals. Also, tests were made for the two parameters with
one, two, and three FM signals being introduced to selected receivers. With
each combination, the effect of an Emergency-Locator-Transmitter (ELT) was
determined .
The laboratory tests were conducted in a large screen room using the arrange-
ment shown in the block diagram of figure 11. Not shown is an audio sweep
generator used to modulate one of the signal generators. During certain
tests on the NAV receivers, the Precision ILS/VOR Signal Generator, Cossor
type CRM555 was used in lieu of an HP 8640B signal generator.
The ELT used in all of the tests in this report was a Leigh/SHARC-7. (At no
time during the tests was the ELT energized.) The location of the SHARC-7
antenna was changed from 3 1/2 inches (9 centimeter (cm)) to 5 feet (152 cm)
from the VHF 137X antenna to test for the AGC level response. Testing showed
that in the particular environment of the lab a maximum effect was achieved
with 4 feet (122 cm) of separation.
While the Narco-10 ELT was tested to determine its effect on receivers, none
was observed at the maximum power levels using the HP signal generators. The
maximum level at the ELT was approximately +3 dBm, depending on the frequencies
of the FM signal generators.
10
The test environment was found to be frequency sensitive. During the test it
was necessary to monitor the receiver and ELT FM signal inputs with a
Tektronix spectrum analyzer. Loss through the splitters was approximately
10 dB, but due to the nonlinear frequency response the loss varied between
5 and 15 dB for frequencies between 88 MHz and 136 MHz.
The results of these tests were plotted using the HP-Mosely 2 DR-2. For these
tests the HP 8660B signal generator was set at a center frequency and swept an
appropriate amount either side to achieve the plots presented. For sensitivity
curves the center frequency selected was usually 98.0 MHz and this was swept
+10 MHz from 88 MHz to 108 MHz.
The receivers tested in the laboratory were all those of the flight test plus
the EDO-AIRE PRT-551. Sensitivity using multiple FM signals and selectivity
plots of the Bendix receiver were not produced as there appeared to be no inter
ference generated from the FM intermodulation signals; however, during flight
testing some interference to the Bendix receiver was observed.
The figures presented may have the signal generator "settings" given, in which
case an average 10 dB must be subtracted to reach the actual level at the
ELT and receiver. A representative sample has been selected to illustrate the
effects of strong FM signals on avionic receivers. The curves shown were made
by the AGC driving the Y amplifier of the X-Y plotter and sweep voltage from
the signal generator (SG-2) driving the X amplifier. The levels of AGC vol-
tage are not directly relatable to the interference consequently a distortion
meter was used to monitor the output of the receiver under test. The meter was
set to monitor the distortion at 1 kilohertz (kHz). As the test progressed,
the meter reading was at times paired with an aural evaluation of the inter-
ference. Aurally, the distortion above 15 percent became objectionable to
those recording the data.
Receiver Selectivity. Measurement of selectivity is the "true selectivity
of the receiver where two or more simultaneous signals are applied and the
effects on the receiver include desensitization, cross-modulation, and signal
breakthrough. Representative selectivity response curves are presented in
figures 153 through 186. Loss of selectivity is evidenced by observing the
increase in the width of the curve detent (bandpass) or decrease in the depth
of the detent (skirt).
The response of the receivers to frequency combinations is not uniform
with regard to signal levels nor relative to whether the ELT antenna was con-
nected or not connected. Consequently, analysis of each group of curves will
not be attempted; however, a limited number of the figures will be discussed
to highlight important points.
The general shape of selectivity response curve for the particular
King 195 receiver tested are represented by figures 168 and 169. In figure
169 two intermodulation FM signals were added to the 118.1 MHz AM signal at
-50 dBm. The ELT and 137X antennas were separated distances listed in the
legend. The two sets of curves had very similar input parameters
11
with the exception of antenna spacing. The spacing did not have a significant
effect on receiver response. Other tests settled on the larger spacing as
standard for all tests where it was a fixed parameter.
Figures 174 and 175 reflect the increase in distortion which occurs in
the presence of the ELT. In figure 174 the first five curves present the
response of the receiver without the ELT. The distortion of these curves is
to be compared with the higher numbered curves taken when the ELT was con-
nected. The precent of distortion to the 1 kHz audio modulation on the AM
signal at 118.025 MHz is much higher with the ELT connected. The same is true
for a similar comparison in figure 175.
TABLE 3. DISTORTION TEST, GENAVE
FM Signal
AM Signal Inputs
Remarks
SC-1
SG-2
SG-3
SC- 3
106.477 MHz
90.0 MHz
122.8 MHz
122.8 MHz
RCVR ELT
RCVR ELT
with ELT
No ELT
dBm dBm
dBm dBm
Percent
dBm Distortion
Percent
dBm Distortion
-6 0
-6 0
-40 21
-60 13
Unacceptable
-16 -10
-6 0
-60 20
-90 15
Unacceptable
N0N-1NTERM01)
FREQUENCY
100 MHz
90 MHz
122.8 MHz
122.8 MHz
+0.4 0
-6.4 0
-70 6
-70 6
No Interference
A comparison of distortion is presented in table 3 with and without inter-
modulation frequency. The response with the ELT resulted in more severe dis-
tortion, but the ELT effect dropped out below the 0 dBm ELT input as seen in
table 4. These data reflect the critical level of diode action in the ELT
below which the ELT is completely passive.
Tables 3 through 7 percent distortion data from a single AM and FM signal
combination of up to three FM signals. When the ELT is connected, the percent
distortion may be expected to be higher than without the ELT. A very high
level of distortion without the ELT is 36 percent, while with the ELT distor-
tion can rise to 90 percent.
Table 4 reflects the distortion response from two FM signals which pro-
duced an intermodulation interference frequency. Again, response with and
without the ELT is presented. The next to last line of the table reflects the
critical levels that must be at the receiver input to generate interference,
i.e., reduction of signal by 3 dB from -13 to -16 dBm dropped the distortion
from 44 percent to 0 percent. Finally, in table 6 the three FM frequencies were
selected to produce an intermodulation frequency of 121.1 MHz to which the
EDO-AIRE receiver was tuned. As seen, even without an ELT, the distortion
was present at an objectionable level with signal settings at -20 dBm for all
receiver inputs. Again, approximately 10 dB must be subtracted to arrive at
the actual receiver input level of -30 dBm.
12
TABLE 4
DISTORTION TEST, KING 195B
3 FM SIGNALS
Inputs
SC-l
Freq.
MHZ
Rec
-d Bm
ELT
-dBm
Freq.
MHz
sc-;
Rec
-dBm
107.9
10
1
121.3
70
107.9
10
1
121.3
140
107.9
10
-
121.3
140
107.9
10
-
121.3
70
107.9
11
2
98.0
3
107.9
11
-
98.0
3
107.9+
13
0
98.0
*14
107.9
13
-
98.0
14
*SG-2 for
-d Bm 10
to 80
same distortion
+ for 107
.9 reduct
•d to -
lb dBm, Distortion
* 0
ELT
-dBm
Freq .
MHz
SC- 3
Rec
-d Bm
ELT
-dBm
Distorts
Percent
-
94.5
2
1
46
-
94.5
2
1
46
-
94.5
2
-
0
-
94.5
2
-
11
3
94.5
4
2.5
46
-
94.5
4
-
23
13
94.5
13
1
44
_
94.5
13
-
0
TABLE 5. DISTORTION TEST 3, EDO-AIRE
SG-2 AM Mod. 1 kHz 118.1 MHZ
Distortion
(~dBM) (Percent)
60
11
70
10
80
10
90
16
100
26
120
26
Tables 3 and 7 are presented to show the effect on the distortion for
particular FM interference levels for two different receivers. The levels
at which distortion becomes objectionable would not be expected in terminal
areas near airports unless the transmitter site is located several miles from
the airport. The first table (Genave Alpha 10) shows the condition of inter-
modulation and nonintermodulation signals with the ELT. Table 5 data were
recorded without any FM interference signals. The observation is made that
with intermodulation signals, interference will probably occur even at high
VHF signal levels.
13
TABLE 6
DISTORTION TEST 4, EDO-AIRE
Signal
Generator
Settings
Distortion ELT
SG-1
SG-2
SG-3
With
Without
dBm
dBm
dBm
Percent
Percent
5
0
15
36
0
-10
0
29
-10
-20
-10
25
-20
-20
-20
25
-20
30
-20
11
10
10
10
90 (no Audio 40-1200)
0
10
0
84
0
0
0
47
-10
-10
-10
29
-20
-20
-20
24
-20
-30
-20
10
TABLE 7
DISTORTION
TEST,
KING 195B, 2FM
SIGNALS
FM Signal
Inputs
AM
Signal
Inputs
Remarks
SG-1
SG-2
SG-3
SG-3
103.
33 MHz
90 MHz
127
MHz
127 MHz
RCVR
ELT
RCVR ELT
With
ELT
No ELT
With ELT
dBm
dBm
dBm d Bm
Percent
dBm Distortion
Percent
dBm Distortion
0
0
-0 0
-60
19
-65
Noticed
0
0
-6 0
-65
Unacceptable
0
0
-6 0
-70
37
-70 5
Worse
104 ,i
085 MHz
90 MHz
118.025
MHz
-0.8
0
-6 0
-30
8
-65
Noticed
-0.8
0
-6 0
-35
-
-
Unacceptable
-0.8
0
-6 0
-40
27
-70
Worse
-10
-10
-6 0
-40
9
-70
Noticed
-10
-10
-6 0
-50
26
Unacceptable
-10
-10
-6 0
-60
26
Worse
In figure 177 the level of the AM signal at 122.8 MHz is maintained at
-60 dBm through the first 8 curves. The levels of the two FM signals are
decreased progressively from curve 1, while selectivity progressively improves.
This response to the intermodulation interference is considered to be typical.
Figures 178 through 180 contain additional data for two FM signals of an inter-
modulation combination with an on-frequency AM signal. Figure 181 presents
the condition of two FM signals at high power levels, but not an intermodulation
combination at the frequency to which the receiver was tuned. Without the
ELT connected, a comparison of curves 12 and 16 shows the distortion percentage
to be the same. Curve 16 was made without the strong FM signals. Comparison
of the curves shows the effect of the FM signals to be that of a higher AGC
voltage base line for curve 12. Noticeable on this figure is that the ELT when
connected had little or no observed effect on the receiver performance as con-
trasted with figure 182. The curves 1 and 2, 6 and 7 of the latter figure are
examples of ELT effect on the receiver. Between ELT input levels of -8.8 and
-14.0, as seen by curves 5 and 4 respectively, there is a sharp reduction of ELT
effect. Figure 183 is a plot of receiver response when the interference FM
frequencies did not produce an intermodulation frequency at the frequency to
which the receiver was tuned. The FM signal levels were maintained at 0.4 dBm
throughout the test. The AM signal generator was swept between 117.9 MHz
and 118.3 MHz, and the output set for each curve as listed in the table.
Curves 2 through 9, plotted with the ELT connected, illustrate the inter-
ference from the ELT when compared to curves 10 through 15 made without the
ELT connected. Curve 2 made with the ELT connected shows the large shift in
AGC voltage from the level of curve 1 which occurred due to the ELT. Review
of figures 184 and 185 provides further examples of ELT adverse effect on the
selectivity of the receiver and increased distortion present with the ELT con-
nected in the laboratory configuration.
In figure 186 the base lines of the three sets of curves were shifted to
prevent overlaying and for clarity. As with previous examples, the interfer-
ing FM signals have caused AGC voltage to develop, resulting in a loss of
selectivity. When the interfering signal levels reach the high level of the
lower set (curves 8-13) selectivity has become a small percentage of the
original design selectivity when compared to the top set (curves 1-6) .
The distortion increases to very high levels with increasing interference
signal levels. The observation should be made that any calculation of potential
interference for a general aviation receiver in the presence of strong FM
signals should not be based on the specified selectivity of -60 to -70 dBm.
Receiver Sensitivity AGC Response. The sensitivity in a receiver deter-
mines the extent it is capable of receiving a desired signal. The desired
signal level curve used as a reference contains only the desired AM signal.
Deterioration of sensitivity is reflected in the curves displaying a diver-
gence from the reference when FM signals are applied. The figures on sen-
sitivity of receiver AGC response are organized by receiver type. Test
results of all receivers were not obtained for single AM and multiple FM
interference signals, but an adequate number were conducted to provide a
15
r
1
satisfactory guide to general aviation avionic receivers performance. As with
most tests, hindsight would have resulted in different test conditions; however,
of the many figures a few will be reviewed in detail to point out aspects con-
sidered important.
Figure 187 is representative of curves for receivers tested showing
Escort 110 receiver response to single FM signals of 0, -10, and -20 dBm rela-
tive to an AM signal which was discretely set between -65 and -85 dBm. In the
legend of the figure, AM signals are shown in parenthesis, and as in curve 2
are combined with an FM signal of -20 dBm. Short sections of an X-Y plot are
presented for the three AM frequencies tested. For the tests the FM signal
generator was swept from 88 to 108 MHz on an 18-inch plot. The response across
the entire band/18-inch plot is well represented by these short sections as
levels did not vary significantly across the entire plot.
The receiver sensitivity of figure 187 is unaffected by the FM signal
once the AM signal is at least -65 dBm even for an FM signal of 0 dBm. At a
level of -75 dBm for the AM signal (curve 4), the AGC voltage is increased by
an FM signal of at least -20 dBm since the level is the same for -10 dBm and
0 dBm (curve 5). The distance between curves 1 and 6 represents 20 dB; there-
fore, depending on the AM frequency, the introduction of -10 dBm FM signal
(curve 3) results in a 10 dB or more loss of sensitivity.
A test which demonstrates the above occurrence was conducted with the
King 195B. The sensitivity at 118.0 MHz was found to be -105 dBm. The AM
signal level was increased to -95 dBm and modulated at 75 percent with 1 kHz.
An FM signal at 98 MHz was then introduced to the receiver along with the AM
signal via a power splitter. When the FM signal was raised to -20 dBm the
clear audio of 1 kHz became intermittent. At -10 dBm the AM audio was com-
pletely lost and a 10 dBm loss of sensitivity was established. At -75 dBm
AM signal level the effect of the FM signal diminishes until at -65 dBm AM
signal level there is no apparent effect on AGC level by the single FM signal
up to 0 dBm.
The curves of figure 188 were produced in the same manner as those of
figure 187. Other figures of this type are shown through figure 227.
For curves 1 through 4 of figure 188 there was no rf input from the FM
signal generators labeled SG-1 and SG-2; however, an X-axis sweep voltage pro-
duced by SG-2 was used to drive the X-Y plotter while the AGC voltage of the
receiver was recorded for an SG-3 input at 108.3 MHz. Several power level
settings were successively set for SG-3 thereby producing the four curves
(levels) shown. Curves 5 through 9 were produced by setting the SG-1 and
SG-2 signal generators to the levels listed. The ELT was connected where an
X is listed under the column for "ELT Con". When the FM signals were intro-
duced, the AGC voltage of the receiver changed from the -75 dBm level as
shown to a lower level. Signal generator SG-1 was held at 103 MHz, while
SG-2 was swept from 88 to 108 MHz. Near the midpoint of the sweep, an inter-
modulation frequency of 108.3 MHz was generated which caused the AGC voltage
of the receiver tuned to 108.3 Mi!z to dip according to curves 5 through 9.
A
16
The settings listed for each of the signal generators are approximately 10 dB
higher than the input levels at the receiver and ELT as described earlier. In
other figures, actual measured input levels may be listed for the receiver
and ELT .
Figures 189 through 193 are additional plots of intermodulation tests
conducted with the Escort 110 receiver. The tests were made with two FM
interfering signals and an AM signal to which the receiver was tuned.
Figure 189 was made using the VOR/ILS simulator in lieu of the standard
AM signal generator. In addition to the AGC response shown in curves 1, 2,
and 3, the remarks column recorded CDI deflection and flag action as the FM
frequency was swept by SG-2 between 88 MHz and 108 MHz. Figures 190 and 191
were plotted for different FM frequency combinations then for figure 189. The
consequence was that many more intermodulation responses were recorded in
figures 190 and 191. The curves show that FM interference effect declined
as the AM signal level increased. In figure 190 the effect was still occur-
ing at -40 dBm AM signal and in figure 191 at -50 dBm some slight effect is
still present.
Figure 193 is a representative example of AGC response. For clarity the
X-Y plotter Y position setting was adjusted to separate the curves; therefore,
the shift does not reflect a change due to FM signal level effect on the AGC
voltage. The AM signal level input to the receiver was held constant at
-70 dBm.
The data block listing curve parameters was placed so as not to obscure
any significant changes in AGC voltage. This is true for all figures of the
report. The values listed in the table are those taken while SG-3 was at a
value of 98 MHz even though, to produce the curves of the figure, SG-3 was
swept from 88 to 108 MHz. Curve 1 was drawn with the ELT antenna connected to
the rf signal generators while curve 2 was drawn with the ELT disconnected
from the generators and the feed line terminated in a 50 ohm load. The signal
generator settings remained the same, but changes to levels of the input to the
receiver changed as listed for curve 2. Usually there was no input level
change observed when the ELT antenna was disconnected.
Several times as the signal generator SG-3 was swept from 88 to 108 MHz an
intermodulation frequency was generated which resulted in AGC voltage response.
Those intermodulation frequencies generated with the exception of the pair at
the top end of the sweep may be attributed to the ELT. The ELT was disconnected
tor curve 2 and all AGC responses indicative of intermodulation frequency were
eliminated except for the pair at the top of the band. A comparison between
curves 5, 7, and 9 indicates the level at which the ELT action on the receiver
was reduced to a low level. Near 0 dBm the reradiation of rf from the ELT
stopped so that no AGC indication of intermodulation was generated for this
receiver .
Figures 195 through 198 present intermodulation test plots on the
Mark 12 receiver using two FM interfering signals and an AM signal produced
by the VOR/ILS simulator to which the receiver was tuned. The curves were
17
plotted with and without the ELT being connected in the test system. The
adverse effect of the ELT is clearly seen. Receiver AGC response varied
between the several figures as a function of what frequency SG-1 was set to
input to the system and the receiver tuning. In figure 195 the receiver was
tuned to 109.1 MHz while in figures 196 through 198 it was tuned to 110 MHz.
Figure 199 shows the Genave and EDO-A1RE receiver AGC response to a
-85 dBm AM signal and the effect of adding a single FM signal to the receiver
sensitivity. In both of these receivers, sensitivity is lost only at the
-85 dBm level AM signal and -20 dBm FM signal. At -75 dBm of AM signal there
is no loss of sensitivity due to a single strong FM signal.
Figure 200 presents the intermodulation test data for the Genave receiver
using three FM interference signals while the receiver was tuned to 122.8 MHz.
No significant intermodulation was recorded with the ELT disconnected, but
with the ELT connected the interference was extensive. A similar result is
repeated in figure 201 where only two FM interference signals were introduced.
The receiver did .however, encounter a small amount of interference with the
ELT disconnected.
Figure 202 was prepared with the receiver tuned to 135.85 MHz. With two
FM signals inputs at high levels, the recorded interference indications were
small even with the ELT connected. In figure 203 this condition is repeated.
Three FM frequencies are introduced and the receiver was tuned to 135.1 MHz
for curves 7 and 8. The general condition observed was that as the receiver
tuned frequency approaches the upper end of the band, the degree of intermodu-
lation interference decreases. Little data was taken at the upper end of the
VHF band for lack of intermodulation interference.
The AGC response to a single FM interference signal using the NAV 400
receiver is presented in figure 204. This receiver appears to lose no sensi-
tivity due to the single FM signal input.
Figures 205 through 208 were plotted for the NAV 400 receiver using two
FM signals and one AM signal to which the receiver was tuned. AGC response
for figures 205, 206, and 208 occurred due to intermodulation interference.
There appeared to be no significant difference in response with and without
the F.LT connected. Figure 208 indicates interference from signal generator
SG-1 tuned to 107.9 MHz while the receiver was tuned to 108.3 MHz.
The King 195B receiver AGC response to a single FM interference signal is
presented in figure 209. A significant shift in ATC voltage due to FM signal
occurred only wxth the -85 dBm signal. A loss of approximately 3 dBm in
sensitivity resulted from a 0 dBm level FM signal. No loss was experienced
in the presence of the -75 dBm AM signal.
Figures 210 through 222 present intermodulation test results for the
King 195B receiver. Figures 210 through 218 were prepared with two FM inter-
ference signals. Figures 210 through 216 held the AM signal generator
18
frequency at 127 MHz while one FM signal generator, SG-2, was swept from
88 MHz to 108 MHz. The third generator, SG-1, was changed to different FM
frequencies as listed on each of the figures. For some frequency selections
of SG-1 there was little intermodulation interference generated as in
figures 210 through 212. In contrast, figures 213 through 216 have high
amounts of intermodulation interference plotted; however, most of the inter-
ference shown on these figures is due to the ELT.
Figure 216 was prepared by holding the two FM signals constant while the
AM signal level was increased. The listed dial settings are 10 dB lower than
the actual signal. As the 127.0 MHz AM level is increased, the effect of the
FM signals is gradually reduced even with the ELT connected. A very high AM
signal level must be reached before the intermodulation interference is over-
come as in curve 7. In this case an input of approximately -45 dBm was
required. In figure 217, where the AM signal was 118.0 MHz, the intermodula-
tion effect was not overcome even at -25 dBm input.
Figure 218 was recorded without the ELT connected for curve 1 while the
other five curves were made with the ELT connected. A significant reduction
to the major AGC deflection did not occur until SG-2 was dropped to a setting
of -10 dBm. The inputs to the receiver for curve 6 were approximately
-10 dBm and -20 dBm respectively for SG-1 and SG-2 remembering the 10 dB dif-
ference between "Setting" and "Input."
Figures 219 and 220 present curves made with three FM interference sig-
nals into the King 195B receiver. Curve 1 of figure 219 is marked to indi-
cate the center frequency of the sweeping signal generator, SG-2, when the
interference AGC response occurred. For curves 7 to 10, the SG-2 center
frequency was shifted to 108 MHz to prevent loss of information at 107.9 MHz.
The values listed in the data block were recorded by setting SG-2 at the listed
frequency. As may be seen from the listed data, only with the conditions of
curve 8 was noise encountered with the ELT being connected.
In figure 220, even though no significant AGC excursions were recorded
for curve 2, remarks note that audio interference occurred in the King 195B.
The noise was a significant increase over normal background noise. Also on
figure 220, curves 3 through 9 were made using the Escort 110 receiver. These
curves reflect severe distortion in the recording of AGC and remarks reflect
significant "Flag" and "To-From" indicator action.
In figures 221 and 222 a different type of intermodulation interference
was briefly tested. The receiver in curve 1 of figure 221 was tuned to
118.9 MHz, the AM signal generator was set at 109.1 MHz, and the FM signal
generator was swept from 88 MHz to 108 MHz. As seen, two frequencies were
recorded as interferences areas on the curve. Two actual field cases of this
type of interference were found at NAFEC. Clear music and voice were heard
on the approaches to runways 31 and 22 at NAFEC while flying in a single
engine aircraft directly above the ILS localizer antenna to runway threshold.
The interference ocurred on communication frequency 118.9 MHz. Two local FM
stations together with the ILS frequencies produced the intermodulation fre-
quency as follows:
19
2 <111.9) - 104.9 = 118.9 MHz
2 <109.1) - 99.3 = 118.9 MHz
The interference effect was reproduced by bench tests on the aircraft
receiver type. Tests showed that at -45 dBm of FM signal and -5 dBm of loca-
lizer signal the interference would result. Figure 222 presents data on the
Com 11A for a test similar to that described above.
Figure 223 shows the effect of antenna separation between ELT and the
137X antenna. As each installation of antennas on board an aircraft may be
unique and certainly different from the laboratory environment, the coupling
between ELT and the VHF avionics antenna cannot be expected to follow that of
this figure.
Figures 224 through 227 illustrate the response of the Com 11A receiver
to two FM interference signals. While the interference recorded with the
ELT connected is severe, significant interference is plotted without the ELT
being connected. Again, when the power to the ELT drops sufficiently, inter-
ference is reduced to a level as if it had been disconnected.
The Bendix receiver was not subject to intermodulation interference in
the form of audio or CDI deflection based on limited laboratory tests. The
effect of a single FM signal with a single AM signal is shown in figure 228.
An FM signal of -20 dBm is capable of shifting the sensitivity downward by
approximately 6 dB.
CDI AND FLAG RESPONSE FROM FM SIGNALS INTO NAV RECEIVER. The CDI displays the
indicated course error resulting from the phase difference between the
"reference" and "variable" 30 Hz and the amplitude difference in the 90 and
150 Hz modulation. Interference from FM signals will affect the modulation
resulting in errors in CDI reading. If strong FM signals desensitize the
receiver where reduced amplitude of modulation is received a flag will appear.
The results of laboratory tests of the FM signals on the NAV receivers CDI
and flag action is generally presented in the tables which follow. These
recordings were made visually from observed flag action and the recordings of
the 8-channel recorder shown in tables 8 to 14. Deflection gain of the
recorder was adjusted so that full-scale deflection left and right of center
was 25 pa in either direction. The maximum deflection of the CDI in table 8
was 8 pa. The variation in CDI current was due to the audio modulation of
SG-3, the ILS simulator, and SG-2 which swept between 30 and 1200 Hz at a
1 Hz rate. SG-1 was modulated at 400 Hz while the receiver was tuned to
109.1 MHz.
Simultaneous with the monitoring of the other receiver parameters, the audio
output was monitored and was significant; status is included under comments
(table 9). Table 10 continues the CDI and flag response with the ELT connected.
Table 11 contrasts the Mark 12 with the Bendix 4165 receiver which did not
experience interference.
20
TABLE 8. INTERMODULATION TEST 1, MARK 12, CDI DEFLECTION
SG-1 90 MHz
SG-2 102 MHz
SG-3 109.1 MHz
CDI Current
(dBm)
(dBm)
( dBm)
(ua)
-80
-80
-60
0
10
10
1 to 8
5
10
2 to 6
0
10
2 to 6
-5
10
1 to 6
-10
10
3 to 6
-20
10
3 to 6
-10
5
-60
3 to 6
0
0
-60
3 to 6
0
-5
-60
0
-10
-60
0 to 2
TABLE 9.
INTERMODULATION TEST 2,
MARK 12, CDI DEFLECTION
Signal
Generator
Settings
Comments
SG-1
SG-2
V0R SIM
90 MHz
102MHz
109.2 MHz
dBm
dBm
dBm
OFF
OFF
-37
Flag at -87
10
10
99.6 MHz
-70
High White Noise Audio
10
10
-70
"FROM", High Audio, 25 yA
5
10
-70
"FROM", High Audio, 25 yA
0
10
-70
+20 yA
-5
10
-70
+10 yA
0
5
-70
25 yA Left, 10 yA Right
0
0
-70
25 yA Left, 10 yA Right
0
-5
-70
20 yA Left, 10 yA Right
0
-10
-
15 yA Left, 10 yA Right
OFF
OFF
-70
15 yA Left, 7 yA Right
10
10
-30
With ELT, PEEPING Flag, Defl.
10
10
-40
PEEPING Flag
10
10
-50
PEEPING Flag
10
10
-60
Full Flag
21
TABLE 10. INTERMODULATION TEST 3, MARK 12, CDI DEFLECTION
O iA m
— I A O O O kA • • iA OO O'
II O O I I I
OOO'AOOOOOOO
CM LA I
• * e O O
w » U3| -H CN
^5 <5* -Ol II
OO'AO'AO'AO'AiA'A
^ < < < <
«M<<< n a a n <
a a a a.
• iA o O
O 00 ^ IN ts H h CO
3000000*^”^
<hhhhhhhh
< TO
oc^ccaaSa
'MJUUUUUUUU
00°0000°°IAO
Ti 7 7 7 I 7
lNf)^iA>0rs00O>O'
25003300000
(AvOaaOcAfAsOMJvOsOvO
22222220000
00000000000
H H fO ^ ^
I I I I I I
B lA N »
01 * • O •— <
U H >0 oo H H
TABLE 11. INTERMODULATION TEST 4, MARK 12 AND BENDIX CDI DEFLECTION
Signal
Generator
Settings
Comments
SG-1
SG-2
VOR SIM
90 MHz
102 MHz
109.2 MHz
dBm
dBm
dBm
0
10
-50
"From" +25 pA
0
5
-50
+25 pA
0
0
-50
18 UA Left, 7 pA Right
0
0
-50
Strong Audio, +25
UA
0
-5
-60
18 uA Left, 12 pA
Right
0
-5
-70
13 pA Left, 13 pA
Right
0
-5
-70
No Deflection
Bendix FA-4165. 3A
0
-10
-30
Flag at - 30 dBm
10
10
-20
High Audio, 0 pA
5
5
ELT
-20
No Audio
10
10
No
ELT
-20
No Audio
OFF
OFF
No
ELT
-20
P.F. AT - 32 dBm
109.
1
10
10
No
ELT
-20
No Intfer., Freq.
Intermod
TABLE 12.
INTERMODULATION
TEST 5, MARK 12
AND BENDIX
CDI DEFLECTION
SG-1
SG-2
SG-3
Remark
MHz
103.6
98.0
109.2
dBm*
-7
-10
-65
To /From
dBm
5
-10
-65
Flag
MHz
107.0
98.0
109.2
dBm
11
-10
-65
To /From
dBm
6
-10
-65
Flag
Bendix FA-4165. 3 A
MHz
103.7
98.0
109.2
dBm
4
0
-35
Flag
dBm
6
0
-35
To/From
MHz
103.1
98
109.1
dBm
1
-10
-75
Flag
dBm
5
-10
-75
To /From
* Signal
General Settings
for all dBm values of this
table.
23
TABLE 13
INTERMODULATION TEST 6, MARK 12 AND BEND IX CDI DEFLECTION
SG-1
SG-2
SG-3
Remark
MHz
103.6
98.0
109.2
dBm*
7
-10
-65
To/From
dBm
5
-10
-65
Flag
MHz
107.0
98.0
109.2
dBm
11
-10
-65
To/From
dBm
6
-10
-65
Flag
Bendix FA-4165. 3A
MHz
103.7
98.0
109.2
dBm
4
0
-35
Flag
dBm
6
0
-35
To /From
MHz
103.1
98
109.1
dBm
1
-10
-75
Flag
dBm
5
-10
-75
To/From
*Signal General
Settings for
all dBm
values of this table.
TABLE
14 . INTERMODULATION
TEST, NAV 400 CDI DEFLECTION
Signal
Generator
Settings
Comments
SG-1
SG-2
ILS SIM
90 MHz
102 MHz
109.1
dBm
dBm
dBm
10
10
-50
Flag F.S. Deflection
5
5
-50
No Deflection
10
10
-50
15 pA Left, 25 pA Right
5
10
-50
10 pA Left, 10 pA Right
0
10
-50
2 pA Left, 9 pTk Right
-5
10
-50
0-5 Right
0
5
-50
0-3 Right
0
0
-50
+2 pA
WITH ELT
5
10
-50
20 pA Left, 25 pA Right
0
10
-50
10 pA Left, 22 pA Right
-5
10
-50
+10 pA
0
5
-50
+ 5 pA
0
0
-50
Bias of 2 pA Right
J
24
Tables 12 and 13 present the levels of FM signal which will produce a shift in
flag condition of "TO" or "FROM". The Bendix in this case is shown to move to
a false Indication with a strong FM signal.
Finally, table 14 presents the results of tests on the NAV 400 using a strong
AM signal. The FM signals must be held at a high level to have significant
effect on CD1 current.
’’Motorboating" sound Interference. A laboratory investigation was accom-
plished on the motorboating sound prevalent in general aviation type receivers
when subjected to multiple commercial FM broadcast environment. Two signal
generators were adjusted to frequencies Fa and F^ respectively to provide a
third intermodulation product (F^ * 2Ffl-F^). Both FM signals from the genera-
tors were applied to a Genave Alpha/10 receiver at 0 dBm level and 75 kHz
deviation with 1000 Hz modulation. If either a or b frequency was varied to
depart from the intermodulation frequency, the intermodulation tone present
was being surmounted by a motorboating sound. As the frequency separation
from the intermodulation was increased, the tone level decreased and the beat
(click) present in the motorboating sound increased in frequency and intensity,
then decreased into receiver noise at approximately 200 kHz departure from the
original frequency setting. If no modulation was applied, only receiver noise
was present.
PREDICTION OF INTERFERENCE. Earlier described laboratory tests have shown that
the FM signal levels for intermodulation interference need not be of equal dBm
levels. The equation for intermodulation used in this report is as follows:
*
AFi + BF2 - CF3 -
Where:
A, B, and C - coefficients 0 to 3
F]_, f2» *3 = radiated interference frequencies
Fi = Interference frequency of intermodulation.
The primary/secondary levels required for each coefficient for a few of the
combinations are listed in table 15. These levels place a third criteria,
power level, as a function of the coefficient on the area of potential inter-
ference. One of the several signals (table 15) must be at a high level (prime)
with a signal of approximately -10 dBm for communication receiver input and
-20 dBm for a navigation receiver, except in the presence of the interfering
ELT when lower levels will produce interference. The other signals, secondary,
of the intermodulation combination (table 15) may be 10 to 20 dB lower and
produce a significant interference on most low-cost general aviation receivers.
25
r
TABLE 15. EXPECTED POWER LEVELS FOR SELECTED COEFFICIENT COMBINATIONS OF
INTERMODULATION EQUATION
Intermodulation Equation AF^ - BF2 - CF3
Coef. A
Level Ft
Coef. B
Level F2
2
Prime
0
-
2
Prime
1
Secondary
1
Prime/ Sec
1 '
Prime/Sec
3
Prime
0
—
Intermodulation Frequency
Coef. C
Level F3
1
Secondary
2
Prime
1
Prime/Sec
2
Secondary
NOTE: Levels maybe interchanged as a function of harmonic output from an FM
station and characteristes of the receiver.
The above information plus an assumption that most FM antennas radiate omni-
directionally has led to the Venn diagram solution of where FM signal combina-
tions might be expected to produce intermodulation interference. For the
Venn-type solution, it was necessary to determine the distance at which the
FM station signal at receiver input would be attenuated to -10 dBm for com-
munication receivers and -20 dBm for navigation receivers. The above two cal-
culations would be the high level or prime FM signal required for a configura-
tion. Appropriate distances must be calculated for secondary level signals of
-20 and -30 dBm in intermodulation combinations. The space loss formula was
used to calculate the distances:
Ls = 38 + 20 log d + 20 log f
Where :
d = distance in nmi
f = frequency in MHz
The HP-65 calculator program (appendix A) has been written for FM and TV brute
force interference calculation which may be used to determine d of the above
equation. When using the calculator, once the program has been entered the
calculator may be operated as follows:
Step
Instruction
Keys
1
2
3
4
5
Initialize RTN, R/S
Enter LS in dB B
Enter frequency of FM in MHz C
Read d in feet D
Read d in nmi E
26
The calculation of LS is modified as follows:
LS = ERP + |pr| - Lr dB
Where:
ERP = Effective radiated power of FM station in dBm
|Pr| = Absolute dBm signal level at receiver i.e., -10, -20, -30
Lr = For NAV antenna: Antenna loss of 3 dB plus 1 dB/MHz below 108 MHz
Lr * For COM antenna: Antenna loss of 10 dB from 108 to 100 MHz plus
2 dB/MHz below 100 MHz
If d is used as the radius of circles, they may be presented as in figure 229.
The value of d will vary as a function of frequency due to the antenna response.
In figure 230 the shaded areas indicate where the conditions are met for
potential interference based on power levels from FM stations A and B, where
-10 dBm is the prime signal level and -30 dBm the secondary. In figure 231
the prime level is reduced to -20 dBm while the secondary level is held at
-30 dBm. The shaded area again indicates the potential area of interference.
Figure 232 illustrates the Topeka, Kansas, area for which power circles have
been drawn around the local FM stations. Based on the required combination
of KSWT, KTOP, and KTPK for an intermodulation frequency of 121.7 MHz, the
figure should be studied to determine the expected area of interference
(crosshatched ) • Interference should be expected in the area common to that
overlayed by the PR = -30 (DCOM) circle of KSWT, the PR = -20 (DCOM) circle
of KTPK, and the PR = -20 circle of KTOP. The area defined as common to
these three circles would be a conservative prediction of interference area
for communication receivers. Recorded data for Topeka indicated that the pre-
dictions was substantially correct. Within the area, the effect of antenna
radiation lobes causes the interference to appear to be intermittent,
depending on the course the aircraft flying through the area. The duration
of interference is frequently only a few seconds, which reflects the lobe
condition of radiation.
Not all areas of radiation may be predicted by the described technique. As
described in NAFEC Technical Letter Report, NA-77-41-LR, "High Power FM
Station Interference to VHF Avionics, Topika, Kansas,” radiation levels
from high-gain FM antennas may at times far exceed the level calculated from
the effective-radiated power of the FM station and the assumption of uniform
omnidirectional radiation due to reflections and lobing in the airspace.
High-gain FM station antennas are usually designed to radiate a pattern no
more than +10° from the horizontal. However, based on flight test data, high-
level signals are usually measured directly above FM antennas.
Loss of Sensitivity. The laboratory tests conducted with single FM signals
into the receivers showed a loss of sensitivity of as much as 10 dB for high-
level FM signal inputs. The loss should not, however, adversely effect recep-
tion in the terminal areas where signal levels are normally expected to be
greater than -75 dBm unless there is an intermodulation frequency present due
27
to the presence of appropriate frequencies. There would not be any audible
interference as a result of the single high-level FM signal. Multiple FM
signals at high levels result in sensitivity loss equivalent to single signals.
Emergency Locator Transmitter Effects. The adverse effect of the ELT
used in laboratory tests and during the flights tests is evident in much of
the data presented. The level of FM signal required to cause interference
from the ELT is at a minimum between -5 and -0 dBm. Below the -5 dBm level,
the ELT ceases to adversely affect its environment. Solutions to the ELT
problem have not been considered. Appropriate action to correct the problem
is necessary as the ELT is a unit covered by a Technical Standard Order (TSO) .
Brute Force Interference. One type of "brute-force" interference is a
condition which results from the proximity of the FM band and the ILS band.
The FM frequencies extends from 88 MHz to 108 MHz where it interferes with the
low end of the ILS band. This type of interference will most often occur only
if the separation is a few hundred kHz, thus, it is present only at the (low
end) of the navigation band. The FM interference is present due to radiation
of on-frequency power within the FCC authorized levels. Proper frequency
engineering will prevent authorization of this condition. The conforming FM
emission is: "Between 120 and 240 kHz removed from the carrier, any emission
must be at least 25 dB below the unmodulated carrier. Between 240 and 600 kHz
removed from the carrier, any emission must be at least 35 dB below the unmod-
ulated carrier. Any emission removed from the carrier by more than 600 kHz
must be at least 80 dB below the level of the unmodulated carrier or at least
43 + 10 logigP whichever is the lesser attenuation ( 'Reference Data for Radio
Engineers,' ITT, Fifth Edition)."
A second type of "brute-force" interference is where the strength of signal
is the critical parameter. Protection against this form of interference is
particularly critical for navigation receivers. The protection procedure should
establish distance from the FAA facility within which interference levels should
not exist. The level must consider the standards for receiver performance.
The scope of the project did not seek to establish such a level.
Finally, no brute force audio modulation was observed during laboratory
tests. The maximum input which could be achieved in most cases was approxi-
mately +5 dBm. Rarely, during flight testing, were FM signal levels on the
spectrum analyzer observed to exceed 0 dBm.
28
CONCLUSIONS
1. Intermodulation interference from FM stations was found to be present at
most locations where flight testing was conducted at low altitude. The loca-
tions were in or near cities which had several high-power FM stations serving
the cities. The interference was most severe near major FM radiation areas
used by several stations. The interference recorded affected both communica-
tion and navigation receivers.
2. A 10 dB increase of rejection in the avionic receivers to FM signals
would nearly eliminate intermodulation interference.
3. Receiver sensitivity and selectivity are significantly reduced by high-
power FM signals .
4. The presence of an FM signal at the prime level in a terminal area
diminishes the number of channels in the VHF avionics band available for
avionic use which will be free of interference to all but high-performance
avionics .
5. Due to avionic antenna frequency response to the FM band, avionic
receivers are less subject to interference of FM signals near 88 MHz.
6. Intermodulation interference at the high end of the VHF communications
band is less frequent and less severe based on receiver response to labora-
tory interference tests.
7. Expected intermodulation interference can be effectively located through
the use of Venn diagram circles whose radii are based on receiver input power
level. However, interference may occur when reflections and radiation char-
acteristics of an FM antenna cause an FM signal to be present at an inter-
modulation power level even though calculated radius based on ERP would indicate
that it should be beyond the range of interference level.
8. Certain ELTs increase the amount of intermodulation interference from
FM stations to VHF avionics due to diode action on FM signals within the ELT
and reradiation of the modified signals to avionic receivers via the ELT
antenna.
29
RECOMMENDATIONS
1. Protect from "prime" level FM signals the ILS and VOR approaches to air-
ports and also those air spaces near airports where communication intermodu-
lation interference is considered hazardous to general aviation. A "prime"
level signal in these areas will adversely affect most general aviation avionic
receivers and establish the conditions which will cause intermodulation with
the presence of an intermodulation "secondary" FM signal.
2. Implement a procedure for analysis of expected FM station interference
from proposed FCC action. The procedure should include both "brute force"
considerations as well as intermodulation prediction based on the Venn dia-
gram approach of this report, in order to adequately protect the communica-
tion and navigation frequencies of the VHF avionic band.
3. Establish a flight test program by Flight Standards Service to determine
the FM spectrum signature and power level at airports which may be subject to
FM interference. Current information on FM airspace power levels is inade-
quate to perform frequency management assignments free of FM intermodulation
interference (particularly for navigation receivers).
30
FIGURE I. ANTENNA TEST RANGE
FIGURE 4. AIRCRAFT ANTENNAS (COLLINS RADIO)
FIGURE 5. AIRCRAFT ANTENNAS (GENERAL AVIATION)
DORNE AND MARGOLIN
DMN-4
w
o
r*
5
& r
<
1 {
CS
ft *
w
■
5 D
J
o?5
- ip**
L) co
FIGURE 6. ANTENNAS EMPLOYED IN FLIGHT TEST
8CHANNi:L RECORDER
GOULD -BRUSH
SPECTRUM ANALYZER
TEKTRONIX 7L 13
FIGURE 7. INTERFERENCE MONITORING EQUIPMENT
38
FIGURE 9
STANDARD
INSPECTION CONSOLES
SIGNAL GENERATOR
HEWLETT PACKARD
8640 B
SIGNAL GENERATOR
HEWLETT PACKARD
8640 B
SIGNAL GENERATOR
SYNTHESIZED
HEWLETT PACKARD
8660 B
SPLITTER
LORD.
PS-261-4CM
EMERGENCY
LOCATOR
TRANSMITTER
SPLITTER
ANZAC
TU-50
TERMINATION
50 OHMS
X-Y RECORDER
H.P. MOSELEY
2 DR- 2
DISTORTION
METER
FIGURE 11. LABORATORY TE^T CONFIGURATION
ARC A-13B
NARCO V R P-15
150 200
FREQUENCY (MHz)
300 350
77-44-12
FIGURE 12. FREQUENCY RESPONSE OF NAVIGATION AIRCRAFT ANTENNAS (GENERAL
AVIATION)
10
FIGURE 13. FREQUENCY RESPONSE OF NAVIGATION AIRCRAFT ANTENNAS (COMMERCIAL)
FIGURE 14. FREQUENCY RESPONSE OF COMMUNICATION AIRCRAFT ANTENNAS (COMMERCIAL)
2
FIGURE 15. HORIZONTAL PATTERN OF NARCO VRP-15 ANTENNA 99 MHz HORIZONTALLY
POLARIZED SOURCE
43
■m
SfTx’iMC ATLANTA INC
i:::!
»••»■••••• ■ - •in
FIGURE 16.
polarizedLsourceRN 0F NARC0 VRP‘15 ANTENNA 110 MHz horizontally
44
IBBBS
STANDARD GAIN ANTENNA
FIGURE 17. HORIZONTAL PATTERN OF NARCO VRP-15 ANTENNA 320 MHz HORIZONTALLY
POLARIZED SOURCE
itmjgmi
WHM
spiv
®aKS8©*£
fflaW1
HilNunt
FIGURE 18. HORIZONTAL PATTERN OF COLLINS 37R-2U ANTENNA 100 MHz VERTICALLY
POLARIZED SOURCE
46
FIGURE 20. HORIZONTAL PATTERN OF COLLINS 37R-2U ANTENNA 320 MHz VERTICALLY
POLARIZED SOURCE
k 8
UBS
,IIflKa*ilaaaaa,ajl
m
180 #4.
SdINIillC
HORIZONTAL PATTERN OF COLLINS 137X-1 ANTENNA 99 MHz
HORIZONTALLY POLARIZED SOURCE
FIGURE 21
: ! :::
:i:i: :
win.
49
?.i itwirir ah»m»
FIGURE 23. HORIZONTAL PATTERN OF COLLINS 137X-1 ANTENNA 320 MHz
HORIZONTALLY POLARIZED SOURCE
6 nmi from threshold
LOCATION:
BENDIX- None
AUDIO INTERFERENCES:
MARK 12- None
FM SPECTRUM
•20 dBm 0098 MHz 300 kHz RES
MARK 12
BENDIX
FRAME 1
FIGURE 24. INDIANAPOLIS - WEIR COOK
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LOCATION - Rwy 4
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
0 dBm 0098 MHz 300 kHz RES
mmmmum
MARK 12
BENDIX
FRAME 2
FIGURE 25. INDIANAPOLIS - WEIR COOK
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over outer marker
LOCATION
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
20 dBm 0098 MHz 300 kHz RES
MARK 12
BENDIX
FRAME 3
FIGURE 26. INDIANAPOLIS - WEIR COOK
LOCATION “ Over airfield
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
20 dBm 0098 MHz 300 kHz RES
MARK 12
BENDIX
FRAME 5
FIGURE 28. INDIANAPOLIS - WEIR COOK
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BEND IX- None
AUDIO INTERFERENCES
MARK 12- Heterodyning
FM SPECTRUM
MARK 12
BENDIX
FRAME 6
FIGURE 29. INDIANAPOLIS - WEIR COOK
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LOCATION - 310 R/20 nmi from SHB VORTAC
BENDIX-Nonc
AUDIO INTERFERENCES
MARK 12-Music
FM SPECTRUM
10 dBm 0098 MHz 300 kHz RES
MARK 12
BEND IX
FIGURE 31. INDIANAPOLIS - WEIR COOK
FRAME 8
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LOCATION - 310°R/23 nmi from SHB VORIAC, over ANTENNA #2
BEND IX- None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
CD I
AGC
-20 dBm 0098 MHz 300 kHz RES
■ ;.i * ■*
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BENDIX
77-44-32
FRAME 9
FIGURE 32. INDIANAPOLIS - WEIR COOK
iMPwrappwiiJiirpvii'aRfij
LOCATION- 130°R/17 nml from SUB VORTAC over ANTENNA #3
BENDIX-None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
MARK 12
BENDIX
FRAME 10
FIGURE 33. INDIANAPOLIS - WEIR COOK
LOCATION - Between middle and outer marker
BENDIX-None
AUDIO INTERFERENCES
MARK 12- Aircraft Engine Noise
FM SPECTRUM
MARK 12
BEND IX
FRAME 1
FIGURE 34. KANSAS CITY - FAIRFAX
20 dBm 0098 MHz 300 kHz RES
m -*>. *****
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LOCATION - 320°R/13 nmi from VORTAC
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
10 dBm 0098 MHz 300 kHz RES
MARK 12
BENDIX
FRAME 5
ANSA S CITY - FAIRFAX
rp ■
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LOCATION - 308°R/13 nmi from VORTAC over ANTENNA #4
FM SPECTRUM
AUDIO INTERFERENCES
CDI
AGC
MARK 12
FIGURE 39. KANSAS CITY - FAIRFAX
BENDIX- None
MARK 12-None
BENDIX
FRAME 6
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BENDIX- High Background Noise
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FIGURE 41. KANSAS CITY - FAIRFAX
FRAME 8
LOCATION - 360 R/13 nmi from VORTAC, over ANTENNA #6
BENDIX-Motorboating sound
MARK 12- Music
FM SPECTRUM
10 dBm 0098 MHz 300 kHz RES
AUDIO INTERFERENCES
5 MHz
MARK 12 f" n
BENDIX
J
77-44-42
FIGURE 42. KANSAS CITY - FAIRFAX
FRAME 9
10 dBm 0098 MHz 300 kHz RES
LOCATION - 315°R/13 nmi VORTAC, between ANTENNA #8 and #4
AUDIO INTERFERENCES
BENDIX- None
MARK 12- Music
FM SPECTRUM
j
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BENDIX
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FIGURE 43. KANSAS CITY - FAIRFAX
FRAME 10
FIGURE 44
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FIGURE 47
TOPEKA
7 nmi from threshold
LOCATION
BEND IX- None
AUDIO INTERFERENCES
MARK 12- None
FM SPECTRUM
MARK 12
BENDIX
FRAME 2
FIGURE 48. TOPEKA - PHILIP BILLARD
3 nmi from outer marker
LOCATION
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
20 dBm 0098 MHz 300 kHz RES
MARK 12
BENDIX
FRAME 3
FIGURE 49. TOPEKA - PHILIP BILLARD
4 nmi from threshold
LOCATION
BEND IX— None
AUDIO INTERFERENCES
MARK 12-Music
FM SPECTRUM
BEND IX
FIGURE 50. TOPEKA - PHILIP BILLARD
FRAME 4
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LOCATION - 4 nmi from threshold
BENDIX- None
AUDIO INTERFERENCES
MARK 12-Music and speech
FM SPECTRUM
MARK 12
BENDIX
FRAME 5
FIGURE 51. TOPEKA - PHILIP BILLARD
r~i
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AD-A058 903 NATIONAL AVIATION FACILITIES EXPERIMENTAL CENTER ATL— ETC F/G 20/14
INTERFERENCE IN COMMUNICATIONS AND NAVIGATION AVIONICS FROM COM— ETC (U)
JUN 78 EM SAMTELLE' J G DONG
UNCLASSIFIED FAA-NA-77-44 FAA-RD-78-35 NL
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BENDIX-None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FRAME 6
FIGURE 52. TOPEKA - PHILIP BILLARD
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LOCATION ” Back course
BEND IX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FRAME 8
FIGURE 54. TOPEKA - PHILIP BILLARD
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LOCATION - 250°R/24 nmi from Topeka VOR
BENDIX-None
AUDIO INTERFERENCES
MARK 12— Music
FM SPECTRUM
MARK 12
BEND IX
FRAME 9
FIGURE 55. TOPEKA - PHILIP BILLARD
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LOCATION - 260°R/10 nmi from Topeka VOR
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FIGURE 58. TOPEKA - PHILIP BILLARD
FRAME 12
BEND IX
CD I
AGC
MARK 12
FIGURE 59. DENVER - JEFFERSON COUNTY
FRAME 1
LOCATION - Rwy 29R, over outer marker
BENDIX-None
MARK 12-Music
FM SPECTRUM
AUDIO INTERFERENCES
-10 dBm 0102 MHz 300 kHz RES
LIN
2 MHz
LOCATION
over outer marker
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Music
FM SPECTRUM
MARK 12
BENDIX
FIGURE 60. DENVER - JEFFERSON COUNTY
FRAME 2
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LOCATION - RNAV Rwy 29R
over middle marker
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Music
FM SPECTRUM
MARK 12
BEND IX
FIGURE 61. DENVER - JEFFERSON COUNTY
FRAME 3
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LOCATION - RNAV Rwy 29R
over outer marker
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
MARK 12
BENDIX
FRAME 4
FIGURE 62, DENVER - JEFFERSON COUNTY
r 7 !
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LOCATION - 260°R/14 nmi from Denver VORTAC
BENDIX- None
AUDIO INTERFERENCES
MARK 12- High Background Noise
FM SPECTRUM
MARK 12
BENDIX
FRAME 5
FIGURE 63. DENVER - JEFFERSON COUNTY
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LOCATION- 258 R/I3.5 nmi from Denver VORTAC
AUDIO INTERFERENCES
BENDIX- None
MARK 12- High Background Noise
FM SPECTRUM
20 dBm 0100 MHz 300 kHz RES
2 MHz
MARK 12 !
BENDIX
r T T
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77-44-64
FIGURE 64. DENVER - JEFFERSON COUNTY
FRAME 6
LOCATION - 240°/25 nmi from Denver VORTAC, Over ANTENNA #4
BEND IX- None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
10 dBm 0100 MHz 300 kHz RES
MARK 12
BEND IX
FIGURE 65. DENVER - JEFFERSON COUNTY
FRAME 7
~
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LOCATION - 230°R/20 nmi from Denver VORTAC, over ANTENNA A
BEND IX- None
AUDIO INTERFERENCES
MARK 1 2- Mu s i c
FM SPECTRUM
CD I
AGC
MARK 12
t—
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BENDIX
' ! . i ._ I
77-44-66
FIGURE 66. DENVER - JEFFERSON COUNTY
FRAME 8
94
LOCATION - 250°R/19 nmi from Denver VORTAC
AUDIO INTERFERENCES
BEND IX- None
MARK 12- Motorboating Sound
FM SPECTRUM
-10 dBm 0100 MHz 300 kHz RES
2 MHz
ij-
MARK 12
:
'till
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77-44-67
FIGURE 67. DENVER - JEFFERSON COUNTY
FRAME 9
95
LOCATION - 230°/25.5 nmi from Denver VORTAC, over ANTENNA #4
AUDIO INTERFERENCES
BENDIX- None
MARK 12- High Background Noise
FM SPECTRUM
CDI
AGC
MARX 12
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77-44-68
FIGURE 68. DENVER - JEFFERSON COUNTY
FRAME 10
LOCATION - 230°R/21 nmi from Denver VORTAC
over ANTENNA A
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
10 dBm 0100 MHz 300 kHz RES
MARK 12
BENDIX
FRAME 11
FIGURE 69. DENVER - JEFFERSON COUNTY
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LOCATION - 220°R/21 nmi from Denver VORTAC
BENDIX- None
AUDIO INTERFERENCES
MARK 12-Di-storted Voice
FM SPECTRUM
0100 MHz 300 kHz
MARK 12
BENDIX
FRAME 12
FIGURE 70. DENVER - JEFF)-
LOCATION - 270°R/18 nmi from Denver VORTAC, over ANTENNA #8
AUDIO INTERFERENCES
BENDIX- None
MARK 12- Motorboating sound
FM SPECTRUM
CD I
ACC
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77-44-71
FIGURE 71
DENVER - JEFFERSON COUNTY
FRAME 13
LOCATION “ 235°R/22 nmi from Denver VORTAC, over ANTENNA A
AUDIO INTERFERENCES
BENDIX- None
MARK 12- Music
FM SPECTRUM
Blank Video Recording
CD I
AGC
LOCATION - 060°/20 nmi from Denver VORTAC , over ANTENNA #4
BENDIX-
AUDIO INTERFERENCES Blank Recording
MARK 12-
FM SPECTRUM
MARK 12
Blank Video Recording
CD1
AGC
BENDIX
FIGURE 73
DENVER - JEFFERSON COUNTY
FRAME 15
LOCATION - 050°/ 19 nmi from Denver VORTAC
BEND IX-
AUDIO INTERFERENCES Blank Recording
MARK 12-
FM SPECTRUM
FIGURE 74
DENVER - JEFFERSON COUNTY
FRAME 16
LOCATION - 050°R/20 nmi from airfield, between ANTENNAS #6 and #1
AUDIO INTERFERENCES
BEND IX- None
MARK 12- Distorted Voice
FM SPECTRUM
FIGURE 75. ALBUQUERQUE - INTERNATIONAL
FRAME 1
i3
LOCATION - 060°R/20 nmi from airport, between ANTENNAS #1 and #2
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Distorted Voice
FM SPECTRUM
20 dBm 0098 MHz 300 kHz RES
MARK 12
BENDIX
FIGURE 76. ALBUQUERQUE - INTERNATIONAL
FRAME 2
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BEND IX-
AUDIO INTERFERENCES
MARK 12- Distorted Voice
FM SPECTRUM
MARK 12
BENDIX
FRAME 3
FIGURE 77. ALBUQUERQUE - INTERNATIONAL
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nmi from Albuquerque VORTAC
LOCATION
BEND IX- Motorboating Sound
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
10 dBm 0098 MHz 300 kHz RES
i « * •»* j
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MARK 12
BENDIX
FRAME U
ALBUQUERQUE - INTERNATIONAL
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LOCATION
BENDIX-None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
10 dBm 0098 MHz 300
Mlti-Ms
MARK 12
BENDIX
FIGURE 79. ALBUQUERQUE - INTERNATIONAL
FRAME 5
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LOCATION - 063 R/12 nmi from VORTAC
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Motorboating Sound
FM SPECTRUM
10 dBm 0098 MHz 300 kHz RES
MARK 12
3ENDIX
FRAME 6
FIGURE 80. ALBUQUERQUE - 1 UTERI! AT IONA
108
LOCATION - 063°R/12 nmi from VORTAC
BENDIX-None
AUDIO INTERFERENCES
MARK 12- Distorted Voice
FM SPECTRUM
MARK 12
BEND IX
FIGURE 81. ALBUQUERQUE - INTERNATIONAL
FRAME 7
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LOCATION - 063°R/8 nmi from VORTAC, over ANTENNA #4
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FRAME 8
FIGURE 82. ALBUQUERQUE - INTERNATIONA.
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LOCATION - 063°R/I2 nmi from VORTAC, over ANTENNA #3
AUDIO INTERFERENCES
BENDIX- None
MARK 12- Motorboating sound
FM SPECTRUM
Blank Video Recording
CD I AGC
77-44-83
FIGURE 83. ALBUQUERQUE - INTERNATIONAL
FRAME 9
111
LOCATION - 078°R/between outer marker and VORTAC
AUDIO INTERFERENCES
BEND IX- None
MARK 12- Motorboating Sound
FM SPECTRUM
Blank' Video Recording
CD I
AGC
MARK 12
BEND IX
FIGURE 84. ALBUQUERQUE - INTERNATIONAL
FRAME 10
112
LOCATION - 078°R/8 nmi
AUDIO INTERFERENCES
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BENDIX-None
MARK 12- Motorboating Sound
FM SPECTRUM
«
Blank Video Recording
\
CDI
AGC
MARK 12
BENDIX
FIGURE 85. ALBUQUERQUE - INTERNATIONAL
FRAME 11
3
LOCATION - Rwy 4, over VORTAC
AUDIO INTERFERENCES
BENDIX-None
MARK 12-Motorboating Sound
FM SPECTRUM
Blank Video Recording
FIGURE 86
ALBUQUERQUE - INTERNATIONAL
FRAME 12
LOCATION
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Music
FM SPECTRUM
20 dBm 0100 MHz 300 kHz RES
MARK 12
BEND IX
FRAME 1
FIGURE 87. SAN ANTONIO - INTERNATIONAL
1 '
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10 dBm 0100 MHz 300 kHz RES
LOCATION - \ nmi from outer marker
AUDIO INTERFERENCES
BENDIX-None
MARK 12- Music
FM SPECTRUM
2 MHz
MARK 12
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BENDIX
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77-44-88
FIGURE 88. SAN ANTONIO - INTERNATIONAL
FRAME 2
MARK 12
LOCATION - Over outer marker
AUDIO INTERFERENCES
BENDIX-None
MARK 12- Music
FM SPECTRUM
CD I
AGC
BENDIX
FIGURE 89. SAN ANTONIO - INTERNATIONAL
FRAME 3
2 MHz
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Over outer marker
AUDIO INTERFERENCES
BENDIX— None
MARK 12- Music
MARK 12
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77-44-90
FIGURE 90. SAM ANTONIO - INTERNATIONAL
FRAME 4
1 18
LOCATION - -2 nni from outer marker
AUDIO INTERFERENCES
BENDIX- None
?-lARK 12- Motorboating Sound
FM SPECTRUM
-10 dBm 0100 MHz 300 kHz RES
MARK 12
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77-44-91
FIGURE 91. SAN ANTONIO - INTERNATIONAL
FRAME 5
LOCATION - 1 nmi from outer marker
BENDIX-None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
AGC
77-44-92
FRAME 6
CD I
- INTERNATIONAL
MARK 12
BEND IX
FIGURE 92. SAN ANTONIO
j
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LIN
2 MHz
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20 dBm 0100 MHz 300 kHz RES
LOCATION - 177°R from San Antonio VORTAC, over ANTENNA #5
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
CDI
ACC
MARK 12
BENDIX
FIGURE 93. SAN ANTONIO - INTERNATIONAL
FRAME 7
mmmmm
2 MHz
LOCATION- 177°R/7 nmi from VORTAC, over ANTENNA #2
AUDIO INTERFERENCES
BENDIX- None
MARK 12- Motorboating Sound
FM SPECTRUM
CDI
ACC
jV
FIGURE 94. SAN ANTONIO - INTERNATIONAL
FRAME 8
122
over ANTENNA #5
LOCATION - 12 nmi from VORTAC
BEND IX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FRAME 9
FI CURE 95. SAN ANTONIO - INTERNATIONAL
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LOCATION - 177°R/I4 nmi from VORTAC
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Motorboating Sound
FM SPECTRUM
MARK 12
BEND IX
FRAME 10
FIGURE 96. SAN ANTONI 0 - INTERNATIONAL
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LOCATION - 177°R/15 nmi from VORTAC
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
10 dBm 0100 MHz 300 kHz RES
MARK 12
BENDIX
FIGURE 97. SAN ANTONIO - INTERNATIONAL
FRAME 11
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LOCATION - 13 mv.i from VORTAC, over cluster of ANTENNAS
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
MARK 1
BENDIX
\rJ\^s
FIGURE 98. SAN ANTONIO - INTERNATIONAL
‘I
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LOCATION - 158°R/6 nmi from VORTAC
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FIGURE 99. SAN ANTONIO - INTERNATIONAL
FRAME 13
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MHz 300
kHz RES
RTTT7
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LOCATION - 158°R/9 nmi from VORTAC, over 4 ANTENNAS
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FIGURE 100. SAN ANTONIO - INTERNATIONAL
FRAME 14
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LOCATION- 158°R/16 nmi turning
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
MARK 12
BENDIX
FIGURE 101. SAN ANTONIO - INTERNATIONAL
FRAME 15
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LOCATION - 158 R/I3 nmi from VORTAC
BENDIX-None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
MARK 12
BENDIX
FIGURE 102. SAN ANTONIO - INTERNATIONAL
FRAME 16
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LOCATION
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Music
FM SPECTRUM
BLANK (NO ALPHANUMERIC
MARK 12
BENDIX
FIGURE 103. HOUSTON - HOBBY FIELD
FRAME 1
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2 nmi from middle marker
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FIGURE 104. . HOUSTON - HOBBY FIELD
FRAME 2
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MARK 12
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LOCATION - 5 nird. from outer marker
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Motorboatrng Sound
FM SPECTRUM
CDI
AGC
BEND IX
77-44-105
FRAME 3
FIGURE 105. HOUSTON - HOBBY FIELD
-
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LOCATION - 1 nmi inside of outer marker
AUDIO INTERFERENCES
BEND IX-N one
MARK 12-Motorboating Sound
FM SPECTRUM
CD I
AC.C
MARK 12
BEMDIX
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FIGURE 106. HOUSTON - HOBBY FIELD
FRAME 4
134
LOCATION - 182°R/17 nmi from Houston VORTAC
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating sound
FM SPECTRUM
20 dBm 0100 MHz 300 kHz RES
MARK 12
BENDIX
1
1
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k
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FIGURE 107
HOUSTON
HOBBY FIEIJ)
fra:i: 5
LOCATION - 182°R/15 nmi from VORTAC
BEND IX- None
AUDIO INTERFERENCES
MARK 12- Motorboating sound
FM SPECTRUM
10 dBm 0100 MHz 300 kHz RES
MARK 12
BENDIX
FRAME 6
FIGURE 108. HOUSTON - HOBBY FIEND
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LOCATION - 160°R/7 nini turning
AUDIO INTERFERENCES
BEND IX- None
MARK 12-Motorboating Sound
FM SPECTRUM
CDI
AGC
MARK 12
i r\
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BENDIX
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77-44-109
FIGURE 109. HOUSTON - HOBBY FIELD
FRAME 7
A
137
LOCATION - 134°r/16 nrai from VORTAC
BENDIX- None
AUDIO INTERFERENCES
MARK 12'
Music
FM SPECTRUM
MARK 12
BENDIX
FIGURE 110. HOUSTON - HOBBY FIELD
FRAME 8
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2 nmi over ANTENNA -3
LOCATION
BENDIX-None
AUDIO INTERFERENCES
MARK 12
FM SPECTRUM
MARK 12
BENDIX
FIGURE 111. UCUSTi
FRAME 9
UOBB F E ( J)
LT
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139
LOCATION - 170°r/13 nmi
AUDIO INTERFERENCES
BENDIX- None
MARK 12- Motorboating Sound
BENDIX
77-44-112
FIGURE 112. HOUSTON - HOBBY FIELD
FRAME 10
140
LOCATION - 1S0°R/12 nni over ANTENNAS #3 and # I
BENDIX- None
AUDIO INTERFERENCES
MARK 1
Motorboatin;; Sound
FM SPECTRUM
MARK 12
BENDIX
FIGURE 11
FRAME 11
LOCATION - Back course, Rv/y 31R, 3 nmi from threshold
AUDIO INTERFERENCES
BENDIX-None
MARK 12- Motorboating Sound
FM SPECTRUM
CDI
AGC
FIGURE 114. DALLAS - LOVE FIELD
FRAME 1
MARK 12
• A ■ i
^ » r V
3ENDIX
77-44-114
LOCATION - Back course
3 nmi from threshold
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FIGURE 115. DALLAS - Lt/VE FIELD
FRAME 2
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LOCATION - Rv/y 31L, 1 runi from middle marker
AUDIO INTERFERENCES
BENDIX-None
MARK 12-Motorboating Sound
FM SPECTRUM
CDI
AGC
BEND IX
• *7 T'
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to
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77-44-116
FIGURE 116. DALLAS - LOVE FIELD
FRAME 3
144
BENDIX
LOCATION - Between middle and outer markers
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
CD I
AGC
FIGURE 117. DALLAS - LOVE FIELD
FRAME 4
...1 ...1 i.. J
77-44-117
MARK 12
aaLaaIIlJL
2 MHz
LOCATION - Between middle marker and threshold
BEND IX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
•10 dBm 0100 MHz 300 kHz RES
MARK 12
BENDIX
FIGURE 118. DALLAS - LOVE FIELD
FRAME 5
mm
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LOCATION -080°R/9 nnd from Greater Southwest (GSW) VORTAC
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
FIGURE 119. DALLAS -
LOVE FIELD AMD REGIONAL FT WORTH /DALLAS FRAME 1
BENDIX
CDI
AGC
MARK 12
20 dBm 0098 MHz 300 kHz RES
2 MHz
LOCATION - 080°R/9 nmi from Greater Southwest (GSW) turning
AUDIO INTERFERENCES
BENDIX-None
MARK 12-Motorboating Sound
FM SPECTRUM
148
LOCATION - 260°R/14 nmi from GSW VORTAC
BEND IX— None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
BENDIX
FIGURE 121. DALLAS - L( VE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 3
I
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LOCATION
over ANTENNA #11
BENDIX- None
AUDIO INTERFERENCES
MARK 12- High Background Noise
FM SPECTRUM
MARK 12
BENDIX
FICURE 122. DAI, US - L( VE FIELD AMD REGIONAL FT Wo.lTH/DALUS FRAME 4
1 — l
r * p *;
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M
1
LOCATION - 230°R/12 nmi from GSW, over ANTENNA #8
AUDIO INTERFERENCES
BENDIX- None
MARK 12-High Background Noise
BENDIX
«i.> a . m» on « iwm » m
. VU ~ 1 1
77-44-123
FICURE 123. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 5
131
LOCATION - 2I0°R/12 nmi from CSW, over ANTENNA #8
AUDIO INTERFERENCES
BENDIX-None
MARK 12-Noise and Motorboating
FM SPECTRUM
CD I
AGC
FIGURE 124. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 6
152
DALLAS - LOVE FIELD AM) REG1C1AL FT WLRTi /DALLAS FRAME 7
153
LOCATION - I60°K/18 runi from GSW turning, over ANTENNA #2
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Music
FM SPECTRUM
MARK 12
BENDIX
DAutAS - LOVE 1-i.ELD A..D REGIONAL FT WORTH /DALLAS FRAME 8
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LOCATION - 135°R/15 nmi from GSW
AUDIO INTERFERENCES
BENDIX-None
MARK 12-High Background Noise
FM SPECTRUM
FIGURE 127. DAuuAS - LoVE FIEuD AI D REGIONAL FT VA.RTK /DALLAS FRAME 9
155
LOCATION - 110°R/15 nmi from GSW
over ANTENNA #6
BENDIX-None
AUDIO INTERFERENCES
MARK 12- Music
MARK 12
BENDIX
FIGURE 123. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 10
\
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LOCATION - 135°R/16 nmi from CSW
AUDIO INTERFERENCES
BENDIX-None
MARK 12-High Background Noise
FM SPECTRUM
1
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CD I
MARK 12
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77-44-129
FIGURE 129. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAM 11
157
LOCATION - 155°R/18 nmi from C.SW, over ANTENNA #2
AUDIO INTERFERENCES
BENDIX-None
MARK 12-Music
FM SPECTRUM
CDI
AGC
MARK 12
|
BEND IX
FIGURE 130
DALLAS - LOVE FIELD AND REGIONAL FT WORD’. /DALLAS
FRAME 12
LOCATION - 170°R/16 nmi from CSW
AUDIO INTERFERENCES
BENDIX-None
MARK 12-i'ludic
FM SPECTRUM
CD I
AC.C
MARK 12
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77-44-131
FIGURE 131. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 13
159
LOCATION - 185°R/14 nmi from GSK
AUDIO INTERFERENCES
BENDIX- None
MARK 12- Music
FM SPECTRUM
m -20 dBm 0100
MHz 300 kHz RES ■
' i1
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2 MHz i
CD I AGC
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BENDIX
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77-44-132
FIGURE 132
DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 14
LOCATION - 200°R/14 nmi Iron' GSW, over ANTENNAS #4 and #10
BENDIX-None
AUDIO INTERFERENCES
MARK 12- Mu sic
FM SPECTRUM
20 dBm 0100 MHz 300 kHz RES
MARK 12
BENDIX
FIGURE 133. DALLAS - LOVE FIELD AND REGIONAL FT WORTN /DALLAS FRAME 13
LOCATION - 210 R/14 n..i fro:. GSW , over ANTENNAS #3 and #10
AUDIO INTERFERENCES
CDI
MARK 12
BEND IX
BENDIX- None
MARK 12- Music
AC.C
77-44-134
•r-Ri; 13/-
DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 16
LOCATION - 165°R/I5 nmi from GSW, over ANTENNAS #1, #4, and #9
BENDIX- None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
MARK 12
BENDIX
FIGURE 135. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 17
nr.
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LOCATION - 125°R/15 nmi rom GSW
BENDIX— None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
CDI AGC
MARK 12
BENDIX
. .i
L. j _]
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j. .!
. qij
J
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77-44-136
FIGURE 136. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 18
164
LOCATION - U0°R/15 n,.i
rov. CSW
over
BEND IX- None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
20 dBm 0100 MHz 300 kHz RES
MARK 12
BEND IX
FIGURE 137. DALLAS - VE FIELD AND REGIONAL FT WORTH/DALLAS FRAME 19
LOCATION - I20°R/16 nmi from CSW
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Motorboating Sound
FM SPECTRUM
MARK 12
BEND IX
FIGURE 138. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 20
LOCATION - 140°R/17 n.i from GSW
77-44-139
FIGURE 139. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 21
AUDIO INTERFERENCES
BEND IX- None
MARK 12- Motorboating Sound
FM SPECTRUM
MARK 12
BEND IX
V-V^
1
J
1
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CDI
AGC
2 MHz
6
LOCATION - 150°R/17 nmi from GSW, over ANTENNA #2
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Motorboating Sound
FM SPECTRUM
MARK 12
BENDIX
FIGURE 140. DALLAS - LOVE FIELD AND REGIONAL FT WORTH/DALLAS FRAME 22
..r : tip
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1
1 : i j - 1
\y
V
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LOCATION
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Motorboating Sound
FM SPECTRUM
10 dBm 0100 MHz 300 kHz RES
MARK 12
BENDIX
FIGURE 141. DALLAS - LOVE FIELD AND REGIONAL FT WORTH/DALLAS FRAME 23
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169
LOCATION - 180°R/15 nmi from GSW
BENDIX-None
AUDIO INTERFERENCES
MARK 12- Motorboating Sound
FM SPECTRUM
20 dBm 0100 MHz 300 kHz RES
MARK 12
BENDIX
FIGURE 142. DALLAS - LOVE FIELD AND REGIONAL FT WORTH/DALLAS FRAME 24
y rr
H
...
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170
LOCATION - 230° R/ 14 nmi from GSW
BENDIX-None
AUDIO INTERFERENCES
MARK 12-Music
FM SPECTRUM
MARK 12
BEND IX
FICURE 143
DALI AS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 25
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LOCATION - I60°R/17 nmi, over ANTENNAS #2 and #3
AUDIO INTERFERENCES
BENDIX-None
MARK 12- Motorboating Sound
FM SPECTRUM
BENDIX
MMHWN. «mnaiM
77-44-144
FIGURE 144. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 26
CDI
AGC
MARK 12
2 MHz
LOCATION
240°R/14 nmi, over ANTENNA #11
AUDIO INTERFERENCES
BENDIX-None
MARK 12-Music
FM SPECTRUM
Blank Video Recording
FIGURE 145. DALLAS - LOVE FIELD AND REGIONAL FT WORTH/DALLAS FRAME 27
3
LOCATION
turning over cluster of ANTENNAS
rum
BEND IX- None
AUDIO INTERFERENCES
MARK 12- Music
FM SPECTRUM
Blank Video Recording
MARK 12
BENDIX
FIGURE 146. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 28
AD-A058 903 NATIONAL AVIATION FACILITIES EXPERIMENTAL CENTER ATL— ETC F/6 20/14
INTERFERENCE IN COMMUNICATIONS AND NAVIGATION AVIONICS FROM COM— ETC (U)
JUN 78 EM SAWTELLEf J G DONG
UNCLASSIFIED FAA-NA-77-44 FAA-RD-78-35 NL
LOCATION - 110 R/ 6 nmi from GSW
AUDIO INTERFERENCES
BENDIX-None
MARK 12-Motorboating Sound
FM SPECTRUM
Blank Video Recording
MARK 12
BENDIX
77-44-148
FIGURE 148. DALLAS - LOVE FIELD AND REGIONAL FT WORTH /DALLAS FRAME 30
LOCATION - Over Love Field, 9 nmi from GSW
AUDIO INTERFERENCES
BENDIX— None
MARK 12- Motorboating Sound
FM SPECTRUM
Blank Video Recording
CDI AGC
FIGURE 149. DALLAS - LOVE FIELD AND REGIONAL FT WORTH/DALLAS FRAME 31
LOCATION - Rwy 17R, 2 nmi from outer marker
AUDIO INTERFERENCES
BEND IX- None
MARK 12- Motorboating Sound
FM SPECTRUM
Blank Video Recording
FIGURE 150
DALLAS - LOVE FIELD AND REGIONAL FT WORTH/DALLAS FRAME 32
FM SPECTRUM NO. 2
( 3 SECONDS LATER )
THAN NO. 1
FM SPECTRUM NO. 3
( 8 SECONDS LATER )
THAN NO. 1
FM SPECTRUM NO. 4
( 12 SECONDS LATER )
THAN NO. 1
FIGURE 151. FM SPECTRirM, BIRMINGHAM -MUNICIPAL, RWY 5
"
T
FM SPECTRUM NO. 1
FM SPECTRUM NO. 2
( 4 SECONDS LATER )
THAN NO. 1
FM SPECTRUM NO. 3
( 8 SECONDS LATER )
THAN NO. 1
FM SPECTRUM NO. 4
( 13 SECONDS LATER )
THAN NO. 1
FIGURE 152. KM SPECTRUM, BIRMINGHAM -MUNICIPAL, ORBIT 5 NMI
•A- I
3
n
lifi
,« • .’Si
I 1
If?
4/4/77 Teat » 3
ZZZ
a
ii
z
■
■
I!
FIGURE 153. SELECTIVITY, AM SIGNAL 108.3 MHz ESCORT (NAV)
FIGURE 156. SELECTIVITY, 1 AM 6. 2 FM SIGNALS, TEST 4 ESCORT (NAV)
4/4/77 T««t #5
FIGURE 157. SELECTIVITY, 1 AM & 2 FM SIGNALS, TEST 5 ESCORT (NAV)
FIGURE 160. SELECTIVITY, 1 AM & 2 FM SIGNALS, TEST 2 ESCORT (COM)
Receiver: NARCO Eicort 110
HI
■ i
Hi
mpi
FIGURE 161. SELECTIVITY, 1 AM & 2 FM SIGNALS, TEST 3 ESCORT (COM)
90 MHz, 400 Hz
FIGURE 162. SELECTIVITY, I AM 5. 2 FM SIGNALS, TEST 4 ESCORT (COM)
4/1/77 Test #2
191
FIGURE 163. SELECTIVITY, 1 AM & 1 FM SIGNALS, TEST 2 ARC NAV 400
FIGURE 164. SELECTIVITY, 1 AM & 2 FM SIGNALS, TEST 3 ARC NAV 400
4/1/77 Te.t #5
FIGURE 166. SELECTIVITY, 1 AM & 2 FM SIGNALS, TEST 5 ARC NAV 400
FIGURE 168. SELECTIVITY, AM SIGNAL 126.25 MHz KING 195B
FIGURE 169. SELECTIVITY, 1 AM 6 2 FM SIGNALS, TEST 2 KING 195B
Receiver: KING 195B
FIGURE 170. SELECTIVITY, MULTIPLE 1, DISTORTION TEST 1 KING 195B
AGC Response Curves, Selectivity (Distortion Measure !)
Receiver: KING 195B
FIGURE 171. SELECTIVITY, MULTIPLE 1, DISTORTION TEST 2 KING 195B
FIGURE 172. SELECTIVITY, MULTIPLE 1, DISTORTION TEST 3 KING 195B
--~-V 8/77 Test f
FIGURE 173. SELECTIVITY, MULTIPLE 2, DISTORTION TEST 1 KING 195B
rj9
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89
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ip
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19
in
mm
n
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99
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99
n
99
19
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m
99
99
' HI
in
n
19
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99
in
mm
n
99
91
19
■1
11
99
99
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Hi
n
91
19
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19
1
is
S!
PS
5
tm
■!
X*
ft
i
S'
in
99!
mm
il
*1
M
m
t
Wl
99m
FIGURE 174. SELECTIVITY, MULTIPLE 3, DISTORTION TEST 2 KING 195B
Curve SO Settings ibm Distortion ' Aursl
No. SG-1 SG-2 SG-3 % Observation
FIGURE 175. SELECTIVITY, MULTIPLE 3, DISTORTION TEST 3 KING 195B
—■■■I
IffilliniWu.W:
FIGURE 177. SELECTIVITY, AM & 2 FM SIGNALS, TEST 2 GENAVE 10
el;
\vmm
FIGURE 178. SELECTIVITY, AH & 2 FM SIGNALS, TEST 6 GENAVE 10
FIGURE 179. SELECTIVITY, AM & 2 FM SIGNALS, TEST 7 GENAVE 10
IfJ! *1 -4 M
r.'..
^1 si
5
. ;
n
i
'
k
ft
R
f '
►
1 :
>
hr
IIFJ
ittl
IK
■*r.i
&Vi
J — _
- - !
FIGURE 182. SELECTIVITY, AM & 2 FM SIGNALS TEST 4 COM 1LA
Zf 1 MJL . UttU*
FIGURE 184. SELECTIVITY, AM & 2 FM SIGNALS TEST 2 EDO-AIRE
4/14/77
FIGURE 186. SELECTIVITY, DISTORTION TEST 1 EDO-AIRE
117 MHz
VERTICAL SCALE
0.4V = 3V (8.9 cm)
LEGEND
FM SIGNAL dBm (AM SIGNAL dBm)
1. (-85) dBm
2. -20(-85)
3. -10(-85), 0(-85)
4. -(-75)
5. -20(-75), -10(-75), 0(-75)
6. (-65), -20(-65) , - 10(-65), 0(-65)
77-44-188
FIGURE 187. AGC RESPONSE, AM & FM SIGNALS ESCORT 110
215
FIGURE 188. INTERMODULATION TEST 1 , 2 FM SIGNALS ESCORT 110
LLJ\%li ZP »•»!
FIGURE 189. INTERMODULATION TEST 2, 2 FM SIGNALS ESCORT 110
FIGURE 191. INTERMODULATION TEST 2, 2 FM SIGNALS ESCORT 110
8
108 MHz
1
2
6
117 MHz
VERTICAL SCALE
IV - 1 3/4" (4.4 cm)
LEGEND
FM SIGNAL dBm (AM SIGNAL dBm)
1. (“85)
2. -20(-85)
3. - 10(-85)
4. 0(-85)
5. (-75), -20(-75)
6. -10(-75), 0(-75)
7. (-65) -20(-65)
8. -10(-65), 0(-65)
7
8
112 MHz
77-44-195
FIGURE 194. AGC RESPONSE, AM & FM SIGNALS MARK 12
222
Rcc. Input Remarks
FIGURE 195. INTERMODULATION TEST 1 , 2 FM SIGNALS MARK 12
FIGURE 196. INTERMODULATION TEST 2 , 2 FM SIGNALS MARK 12
FIGURE 197. INTERMODULATION TEST 3, 2 FM SIGNALS MARK 12
■inia
ivilM
io|
i
FIGURE 198. INTERMODULATION TEST 4 , 2 FM SIGNALS MARK 12
GENAVE EDO-AIRE
VERTICAL SCALE VERTICAL SCALE
0.1V - 1 1/2" (3.8 cm) 0.1V - 11/16" (1.7 cm)
4
4
5
118 MHz
118 MHz
135 MHz
135 MHz
LEGEND
FM SIGNAL dBm (AM SIGNAL dBm)
1. (-85) dBM
2. -20(-85)
3. -10(-85), 0(-85)
4. (-75). -?0(-75), - 10(- 75), 0(-75)
5. (-65), -20(-65), -10(-65), 0(-65)
FIGURE 199. AGC RESPONSE, AM & FM SIGNALS GENAVE, EDO-AIRE
227
Te*t #1 4/13/77
FIGURE 200. INTERMODULATION TEST 1, 3 FM SIGNALS GENAVE
AGC Response Curves, Futed AM Signal
Level, Variable FM Signal Levels
FIGURE 202. INTERMODULATION TEST 13, 2 FM SIGNALS GENAVE
AGC Response Curves
Receiver: EDO-AIRE. PRT-551
FIGURE 203. INTERMODULATION TEST 4 , 3 FM SIGNALS EDO-AIRE
112 MHz
VERTICAL SCALE
1.0 V *= 4 7/8" (12.4 cm)
LEGEND
FM SIGNAL dBm (AM SIGNAL dBm)
1. (-65), -20(-65)
2. - 10(-65), -20(-65)
3. -20(-75) , -10(-75)
4. (-75) , 0(-75)
5. (-85)
77-44-205
AM & FM SIGNALS NAV 400
FIGURE 207. INTERMODULATION TEST 6, 2 FM SIGNALS NAV 400
t
r*
5 i
—
FIGURE 208. INTERMODULATION TEST 7, 2 FM SIGNALS NAV 400
6
6
118 MHz
1
2
3
6
135 MHz
127 MHz
VERTICAL SCALE
9
O.IV ” lb (1,A Cm *
LEGEND
FM SIGNAL dBm (AM SIGNAL dBa)
1. (-65), -20(-65)
2. -10(65), 0(-65)
3. (-75) , -20(-75), -10(-75), 0(-75)
4. -10(-85), 0(-85)
5. -20(-85)
6. (-85)
77-44-210
FIGURE 209. AGC RESPONSE, AM & FM SIGNALS KING 195B
237
m
■1
|
88
188
in
m
ss
B
in
|g
B
■
88
S
I8S
88
m
188
86
s
mm
HP
iHB
mm
mm !
188
88
B
IH|
;
mm
\mw
Bn
m
M ■
mi
mm
HP -
WM
mm
HP ,
'VK
M
|l
m
mm
mw
Bi
• • ,
w
o
M
Curve
No.
2
3
4
1 i
AGC Response Curves. Z FM Signals
FIGURE 212. INTERMODULATION TEST 3C, 2 FM SIGNALS KING 195B
AGC Response Curves with EI.T
Receiver: KING 195B
FM Sign*! Generators: SG-1:
FIGURE 213. INTERMODULATION TEST 2, 2 FM SIGNALS KING 195B
inUm
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3/28/77 T eat #11
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FIGURE 218. INTERMODULATION TEST 11, 2 FM SIGNALS KING 195B
FIGURE 219. INTERMODULATION TEST 2, 3 FM SIGNALS KING 195B
FIGURE 220. INTERMODULATION T!
. n
-d
— 1
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,
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5
AGC Re*ponae Curve*, 3 FM Signal*
Receiver: KING-195B (CURVES 1 4.2); ESCORT 1 10 (
FM Signal Generator*: SC- 1 , SG-2
bOI
1>»t »5 4/H/71
AGC Response Curves, 3 FM Signals
Receiver: King KY-195 (Curves 1 fc 2); 121. 3 MHz
Escort 110 (Curves 3-9) 109.9 MHz
FM Signal Generators: SG- 1 , SG-2,
SG-3: 98 + 10 MHz;
Curves 3 to 9 data taken at
89. 3 MHz
Curve
No.
1
F req.
MHz
90. 5
SG- 1
Inputs
Rec.
dBm
-14
ELT
dBm
-10
Freq.
MHz
105. 9
SG-2
Inputs
Rec.
dBm
-10
ELT.
dBm
-5
F req.
MHz
98
SG-3
Rec.
dBm
5
ELT
dBm
5
REMARKS
SevereAudio Int.
2
90. 5
-14
-
105. 9
-10
-
98
5
-
Aud. Int. Less Sex
-
90. 5
-14. 4
-10. 0
105. 9
-16
-10
98
0
0
W/W.O. ELT
Strong Int.
-
90. 5
-25
-
105. 9
-26
-
98
-10
-
High B. G.
Noise to this level
3
94. 9
0
0
104. 3
-3
0
89. 3
-8
0
"To" up, SLT
CD1 Deflection
4
94. 9
0
-
104. 3
-3
-
89. 3
-8
0
5
94. 9
-5
-6
104. 3
-6
-8
89. 3
-9. 5
-10. 8
"To" up, SLT
CDI Deflection
6
94. 9
-9
-10
104. 3
- 10
-13
89. 3
-9
-17
"Flag" Up
7
94. 9
-15
-16
104. 3
-17
-19
89. 3
-15
-21
"Flag" Up
8
94. 9
- 0
-5
104. 3
-11
-10
89. 3
-18
-9
"To: Up-Sm. Defl
9
94. 9
-6
.
104. 3
-11
.
89. 3
-18
-
I0DULATI0N TEST 3, 3 FM SIGNALS KING 195B, ESCORT 110
249/250
PRECEDING PAGE BLaNK-NOT FILMED
X
mm
FIGURE 223. INTERMODULATION TEST, ELT/REC SEPARATION CHANGE, KING 195B
3/28/77 Te.t #7
FIGURE 224. INTERMODULATION TEST 7 , 2 FM SIGNALS COM 11A
FIGURE 225. INTERMODULATION TEST 8 , 2 FM SIGNALS COM 11 A
3/28/77 Test #9
FIGURE 226. INTERMODULATION TEST 9, 2 FM SIGNALS COM 11A
FIGURE 227. INTERMODULATION TEST 10, 2 FM SIGNALS COM 11A
r
-10(-65), 0(-65)
(-65), -20(-65)
0(-75)
-10(-75), -10(-85), 0(-85)
-20(-75)
(-75)
-20(-85),
(-85)
108 MHz
112 MHz
(-65), -20(-65) , -10(-65), 0(-65)
•20(-75), -10(-75), 0(-75)
(-75)
-10(-85), 0(-85)
-20(-85)
(-85)
(-65)
- -20(-65), - 10(-65)
0(-65)
(-75), -20(-75), 10(-75), 0(-75)
-10(-85), 0(-85)
(-85), -20(85)
117 MHz
FM SIGNAL dBm (AM SIGNAL dBm)
VERTICAL SCALE
0* IV - 7/8- (2.2 cm) 77.^_22g
FIGURE 228. AGC RESPONSE, AM 6. FM SIGNALS BENDIX
258
FIGURE 229. RECEIVER SIGNAL LEVEL DIAGRAM FOR PRDCOM AND PRDNAV
ANTENI
96* 00'
95* 45'
SCALE - NAUTICAL MILES
PLOT OF TOPEKA AREA FM STATIONS AND
VHF RECEIVER POWER LEVEL CIRCLES
95* 30'
77-44-233
FIGURE 232. TOPEKA, KANSAS FM STATION RADIATION POWER CIRCLES
262
APPENDIX A
BRUTE FORCE INTERFERENCE CALCULATION
Instructions
Input
Data/Units
Keys
Output
Data/Units
This program calculates the distance required
between an interfering station and an aero-
nautical receiver to prevent brute force
desensitization, based on the space loss (Ls)
between the two stations.
Initialize
RTN R/S
0.00
Calculate Ls in db (if known, skip to Step 3)
Enter absolute values of the following:
Enter ERF in watts of interfering signal
ERP/Wat ts
ENTER
ERP/Watts
Enter sensitivity in dBm of victim receiver
Sen/dBm
ENTER
Sen/dBm
Enter losses in dB of victim antenna system
Loss/dB
ENTER
Loss/dB
Enter out band bass rej . in dB of victim rec .
Rej/db
A
Ls/dB
Enter Ls in dB (skip if calculated above)
Ls/dB
B
Ls/dB
Enter frequency in MHz of interfering signal
Freq/MHz
C
Freq/MHz
Read distance in feet required between victim
receiver and interfering transmitter
D
Dist/Ft.
Read distance in nautical miles required
E
Dist /nmi
between victim receiver and interfering
transmitter
A-l
Key
Code
Key
Entry
Shown
Comments
Entry
F
31
ST0-3
STK
42
Clear Stack.
P/S
LBL
Reg
43
Clear register
E
CLX
44
Clear X.
RCL-1
R/S
84
Display 0.00
3
LBL
23
/Calculate Ls value
8
A
11
Ain db from absolute
-
+
61
values of effective
2
C- »
51
3507
radiated power,
receiver sensitivity,
system loss, and
0
+
83
F-l
0
00
receiver rejection
log
0
00
RCL-2
1
01
Ls=
♦
♦
81
/ \
STO-4
F
31
fLO Log ERP \(Rec Sen)-
R/S
Log
08
\ .ooy
1
01
(Sys Loss)-(Rec. Re j • )
0
. 00
X
71
+
61
ST 0-1
3301
Store Ls value.
R/S
84
Display Ls value.
LBL
23
(Enter Ls in dB when
B
12
(known w/o calculation.
ST 0—1
3301
Store Ls value.
R/S
84
Display Ls value.
LBL
23
(Enter freq. in MHz
C
13
(of interfering signal.
STO-2
3302
Store freq. value.
R/S
84
Display freq. value.
LBL
23
(Calculate distance
D
14
(in feet.
RCL-1
3401
Ls in dB
3
03
8
08
Dist.fc< =
_ / \_
-
51
2
02
0
00
6080 Log-1 \ 20 /
♦
81
Freq. MHz
F-l
32
■-
08
! -2
3402
Freq. in MHz.
♦
80
b
06
0
00
8
08
0
00
X
71
Code
Shown
Comments
Mi
listers
3303
Store dist. in ft.
Ri
Ls in
84
Display dist. in ft.
dB
23
(Calculate distance
15
(in nautical miles
r2
Freq.
3401
Ls in dB
in MHz
03
08
Dist . nmi +
r3
Dist.
51
/ V.
in ft.
02
00
81
f f Ls-381
Log-1 \ 20 /
Freq. MH?_
r4
Dist .
in nmi
32
08
r5
3402
Freq. in MHz.
3304
Stare dist. in nmi
r6
84
Display dist. in nmi
R7
r8
r9
Labels
A Cal Ls
B Ent . Ls
C Ent Fr.
D Dist. Ft.
E Dist. nmi
0
1
2
3
4
5
6
7
8
9
Flags
1
A-2