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TRACKING AND COMMUNICATIONS DEVELOPMENT DIVISION
INTERNAL NOTE
•’;AlOA^r' M np°?!.Tr- TASK 6G rESI BEP °BT»
STAST™
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TASK 60 TEST RfcFUKl
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H74-26668
Onclas
41407
EVALUATION OF IRIG-A 21 CHANNEL
CONSTANT BANDWIDTH FM MULTIPLEXER
FOR
National Aeronautics and Space Administration
LYNDON B. JOHNSON SPACE CENTER
Houston, Texas
May 1974
LEC- 3558
JSC-09017
TRACKING AND COMMUNICATIONS DEVELOPMENT DIVISION
INTERNAL NOTE
TASK 60 TEST REPORT
EVALUATION OF IRIG-A 21 CHANNEL
CONSTANT BANDWIDTH FM MULTIPLEXER
FOR
SHUTTLE DEVELOPMENT FLIGHT
INSTRUMENTATION
APPROVED BY
TJ7 B. /farmer
Head, Astrionic's Programs Office
TSTpI
Chief, Tracking and Communicl
Development Division
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
LYNDON B. JOHNSON SPACE CENTER
HOUSTON, TEXAS
May 1974
LEC- 3558
JSC-09017
TASK 60 TEST REPORT
EVALUATION OF IRIG-A 21 CHANNEL
CONSTANT BANDWIDTH FM MULTIPLEXER
FOR
SHUTTLE DEVELOPMENT FLIGHT
INSTRUMENTATION
PREPARED BY
_ T - , X 2-3 74-
C. Tj. Haddlck, Principal Engineer
Lockheed Electronics Company, Inc.
LEC
APPROVED BY
NASA
Astrionics Projects Section
L. R. W^fckiny, Manager
Tracking and Communications
Systems Department
Ritterhouse
Astrionics Programs Office
Astrionics Programs Office
Prepared By
Lockheed Electronics Company, Inc.
For
Tracking and Communications Development Division
NATIONAL AERONAUTICS AND SPACE DIVISION
LYNDON B. JOHNSON SPACE CENTER
HOUSTON, TEXAS
May 1974
LEC-3558
ACKNOWLEDGMENTS
This document was prepared by Lockheed Electronics
Company, Inc., Aerospace Systems Division, Houston, Texas,
for the Tracking and Communications Development Division at
the Johnson Space Center, under Contract NAS 9-12200, Job
; Order 18-109. It was written by C. M. Haddick, Principal
Engineer, and approved by W. J. Shannakan, Supervisor of
| Astrionics Projects Section and by L. R. Watkins, Manager
i of Tracking and Communications Systems Department, Lockheed
Electronics Company, Inc.
PRECEDING tMVv,
11
CONTENTS
Section Page
1.0 SUMMARY 1-1
1.1 VCO PERFORMANCE TESTS 1-2
1.2 RECORDED TESTS 1-2
1.3 RF TRANSMISSION TESTS 1-4
1.4 COMPARISON OF TEST RESULTS 1-5
2.0 INTRODUCTION 2-1
2.1 MULTIPLEXER DESCRIPTION 2-1
2.2 TEST DESCRIPTION 2-2
3.0 DISCUSSION 3-1
3.1 VCO PERFORMANCE TESTS 3-1
3.1.1 Static Noise Tests 3-1
3.1.2 Dynamic Data Signal, Harmonic
Distortion 3-5
3.1.3 Phase Error, Channel-to-
Channel 3-5
3.1.4 Crosstalk, Channel- to-Channel . . 3-8
3.2 RECORDING TESTS 3-10
3.2.1 Static Data Signal Noise 3-11
3.2.2 Static Data Signal Noise With
Induced Tape Recorder Flutter . . 3-14
3.2.3 Dynamic Data Signal Harmonic
Distortion 3-14
3.2.4 Dynamic Data Signal Harmonic
Distortion With Induced Tape
Recorder Flutter 3-16
iii
Section Page
3.3 TRANSMITTED TESTS 3-19
3.3.1 Static Data Signal Noise 3-21
3.3.2 Dynamic Data Signal Distortion. . 3-24
4.0 CONCLUSIONS 4-1
4.1 VCO PERFORMANCE 4-1
4.2 RECORDING TESTS 4-3
4.3 RF TRANSMISSION TESTS 4-4
Appendix
A TASK 60 TEST PROCEDURE EVALUATION OF
TWENTY-ONE "A" CHANNEL CONSTANT BANDWIDTH
FM MULTIPLEXER A-l
IV
TABLES
Table Page
I COMPARISON, NOISE AND DISTORTION
MEASUREMENTS 1-6
II STATIC DATA SIGNAL NOISE, pk-p.c PERCENT OF
FULL SCALE, VCO PERFORMANCE TESTS 3-3
III DYNAMIC DATA SIGNAL, PERCENT TOTAL HARMONIC
DISTORTION, SYSTEM BASELINE TEST 3-6
IV DYNAMIC DATA SIGNAL, CHANNEL-TO-CHANNEL PHASE
ERROR, SYSTEM BASELINE TEST 3-7
V CHANNEL-TO-CHANNEL CROSSTALK TEST 3-9
VI TAPE RECORDER SLOT NOISE DATA 3-12
VII STATIC DATA SIGNAL NOISE, pk-pk PERCENT OF
FULL SCALE, RECORDED DATA TEST 3-13
VIII PLAYBACK STATIC DATA SIGNAL NOISE, pk-pk
PERCENT OF FULL SCALE, WITH TAPE RECORDED
FLUTTER, RECORDED DATA TEST 3-15
IX PLAYBACK DYNAMIC DATA SIGNAL, PERCENT TOTAL
HARMONIC DISTORTION, RECORDED DATA TEST ... 3-17
X PLAYBACK DYNAMIC DATA SIGNAL, PERCENT TOTAL
HARMONIC DISTORTION, WITH TAPE RECORDER
FLUTTER, RECORDED DATA TEST 3-18
XI STATIC DATA SIGNAL NOISE, pk-pk PERCENT OF
FULL SCALE, TRANSMITTED DATA TEST 3-22
XII DYNAMIC DATA SIGNAL, PERCENT TOT'LL HARMONIC
DISTORTION, TRANSMITTED DATA TEST 3-25
v
FIGURE
Figure
Page
3-1
Block diagram of laboratory
21 channel constant bandwidth
multiplexer evaluation tests
3-2
• • • •
BW
ABBREVIATIONS AND ACRONYMS
Bandwidth
CBW
Constant Bandwidth
DR
Deviation Ratio
EMR
Electro-Mechanical Research, Inc.
FM
Frequency Modulation
FS
Full Scale
IRIG
Inter-range Instrumentation Group
LPF
Low Pass Filter
SNR
Signal- to-Noise Ratio
THD
Total Harmonic Distortion
V
Volt
VCO
Voltage-Controlled Oscillator
Ch
Channel
Discr .
Discriminator
Freq .
Frequency
Hz
Hertz (Cycles Per Second)
Lao
Laboratory
MHz
Megahertz (Million Cycles Per Second)
Osc
Oscillator
Ref.
Reference
Sel .
Selector
Vdc
Volts Direct Current
dB
Decibel
Vll
dBm Decibels Referred to 1 Milliwatt
dc Direct Current
i.f. Intermediate Frequency
kHz Kilohertz (Thousand Cycles Per Second)
mV Millivolt
max Maximum
pk-pk Peak- to- Peak
rf Radio Frequency
rms Root Mean Square
vs Versus
viii
TASK 60 TEST REPORT
EVALUATION OF IRIG-A 21 CHANNEL
CONSTANT BANDWIDTH FM MULTIPLEXER
FOR
SHUTTLE DEVELOPMENT FLIGHT
INSTRUMENTATION
1 . 0 SUMMARY
A frequency modulated (FM) multiplexer, consisting of
21 IRIG-A constant bandwidth (CBW) voltage-controlled oscil-
lators (VCO's) was tested to determine its suitability for
use in multiplexing 21 data signals which have frequency
ranges of dc to 2 kHz. Tests* were performed with the
composite signal, consisting of the mixed outputs of the
21 VCO’s connected directly to a set of subcarrier discrimi-
nators, with the signal recorded on magnetic tape and played
back through the discriminators (discr.), and with the
signal transmitted by a frequency-modulated (FM) S-band
radio frequency (rf) transmitter to a EM receiver and
through the subcarrier discriminators.
The tape recording tests included test conditions where
tape speed flutter was induced to determine the reduction
in flutter noise which can be obtained by the tape speed
compensation equipment.
The rf transmission test included transmitting the
composite signal at a nominal rf received signal of -73 dBm
*these tests were performed in the Tracking and Com-
munications Development laboratories as Shuttle-in-line,
Task 60B, wideband studies and evaluation.
1-1
and at rf levels of -83 and -86 dBm. The level of -73 dBm
is the estimated minimum equivalent signal level which will
be received from the Shuttle vehicle at a slant range of
5 degrees.
1.1 VCO PERFORMANCE TESTS
These tests were performed with the VCO signals con-
nected directly to the discriminators. The tests included
measurement of peak-to-peak (pk-pk) noise with dc signals
applied to the VCO's, distortion with sine wave signals
applied to the VCO's, crosstalk between received data
signals, and phase error between the received data signals.
The worst case test results are summarized as follows:
Peak-to-peak noise: 0.6% FS at DR=2
3.9% FS at DR=1
Distortion:
Crosstalk:
Phase Error*
0.65% at DR= 2
3 0% at DR=1
2.8% at DR=1
19° at 2.0 kHz (DR=1)
10.1° at 1.0 kHz (DR=1)
18.4° at 1.0 !Hz (DR= 2)
5.6° at 0.5 kHz (DR-2)
1.2 RECORDED TESTS
The multiplexer composite signal consisting of the VCO
output signals was recorded on an intermediate bandwidth
recorder at a tape speed of 60 inches per second. The
1-2
recorded data were played back through the subcarrier dis-
criminators to determine data signal degradation caused by
the recording process. Recordings were also made with
induced tape speed flutter. The worst case test results are
summarized as follows:
No recorder flutter:
pk-pk noise
1.8* FS at DR* 2
6.01 FS at DR=1
distortion
1.0* at DR* 2
3.3% at DR=1
2.41
flutter:
pk-pk noise
2.31 FS at DR* 2
7.0% FS at DR=1
dis tortion
1.95% at DR* 2
4.1% at DR=1
4.5!
c lutter :
pk-pk noise
2.5% FS at Dk* 2
8.0 FS at DR=1
distortion
4.1% at DR* 2
5.5% at DR=1
These results show that the tape speed compensation
equipment is effective in reducing noise on the data signals
that would be caused by uncompensated tape speed flutter.
The significantly higher values of distortion measured
with induced flutter are caused by frequency modulation of
the data signals that results from the induced flutter. The
1-3
tape speed compensation equipment does not correct the
changes in data signal frequency which is caused by the
recorder flutter.
1.3 RF
TRANSMISSION
;ests
The
worst case test results
are
summarized
as follows.
DR=
1
DR
<2
Received
rf level
Percent
Distortion
Noise, 1
pk-pk
FS
Percent
Distortion
Noise, % FS
pk-pk
-73
dBm
3.0
7.0
0.71
1.2
-83
dBm
—
8.0
—
1.4
-86
dBm
8.5
_
1.5
The relatively high peak-to-peak noise level of 7.0 to
8.5 percent of full scale was measured on the data signal
obtained from channel 14A (120 kHz center frequency) at a
deviation ratio of 1. These values were measured with
the VCO frequency set to high and low bandedges. The noise
measured with the VCO set at center frequency was 1.5 percent
of full scale. At a received rf level of -73 dBm, the maxi-
mum peak-to-peak noise measured on the other channels was
4.5 percent of full scale; at a received level of -86 dBm,
the maximum noise on the other channels was 6.0 percent of
full scale. The high noise levels measured on channel 14A
is caused by interference from a 120 kHz refe 'nee signal
in the 120 kHz translator. This interference can be
significantly reduced by the use of a transmitter which has
a lower deviation sensitivity, so that the VCO signals could
1-4
be set to higher values. Such a transmitter was not avail-
able when these tests were performed.
The rf level of -86 dBm was determined to be the
minimum usable level with the available test equipment.
This level produces a calculated receiver i.f. section
signal-to-noise ratio of 13 dB.
1„ 4 COMPARISON OF TEST RESULTS
The worst case noise and distortion measurements for
the test nominal recording and transmission test configura-
tions are summarized in table I to indicate the degradation
caused by the recording and transmission processes.
1-5
6
2.0 INTRODUCTION
Tests wer'' performed to evaluate the performance of a
frequency modulation data signal multiplexer which consists
of 21 IRIG-A constant bandwidth voltage-ccntrolled oscillators.
2.1 MULTIPLEXER DESCRIPTION
The multiplexer contains VCO’s, mixer amplifiers, trans-
lators, and a reference oscillator manufactured by Sonex,
Inc. The multiplexer consists of 21 IRIG-A channel CBW
VCO’s, Sonex part number TEX-3007MD; five . ixer amplifiers,
Sonex part number TEX-3207MD; three translators, Sonex
part number TEX-3802; and one 240 kHz reference oscillator,
Sonex part number TEX 340 2A.
The 21 VCO signals are developed from one group of
IRIG CBW VCO’s, consisting of channels 1A through 6A, and
three groups of IRIG CBW VCO’s, each consisting of channels
1A through 5A. The composite output of the group of 1A
through 6A VCO’s is connected directly to the final mixer
amplifier. The frequencies of the groups of 1A through 5A
VCO’s are translated up to obtain the channel 7A through 21A
VCO frequencies. Channels 7A through 11A are obtained by
using a 120 kHz translating frequency; channels 12A through
16A are obtained by using a 160 kHz translating frequency;
and channels 17A through 21A are obtained by using a
200 kHz translating frequency.
Each of the groups of VCO’s is mounted in a separate
chassis with a mixer amplifier. The three translators,
the reference oscillator, and the final summing amplifier
are mounted in a separate chassis.
2-1
The peak frequency deviation of the IRIG-A channels is
2 kHz. Each of the VCO's can be nodulated by a 2 kHz data
signal if a deviatio; .ratio (DR) of 1 is used. The deviation
F d
ratio is defined as DR » where F, is the VCO peak fre-
quency deviation and F m is the maximum frequency of the data
signal. The VCO deviation ratio is determined by the cut-off
frequency of the low pass filter used at the output of the FM
subcarrier discriminator which recovers the data signal.
In general, the quality of the received data signal is
increased as the deviation ratio is increased. The IRIG-A
channel VCO*s can be used to transmit 1 kHz data signals with
a deviation ratio of 2.
2.2 TEST DESCRIPTION
The purpose of the evaluation tests was to determine
the accuracy which can be expected when the IRIG-A VCO's
are used to multiplex 21 data signals in the range of 0 to
? kHz. In addition, the multiplexer output signal was
recorded on a magnetic tape recorder and transmitted by
a .'-band FM telemetry transmitter to determine the data
signal degradation which would be caused by the recording
and transmission processes.
Static (dc) signals obtained from a precision labora-
tory power supply, and dynamic (sine wave) signals obtained
fro*, laboratory sine wave oscillators were used as simulated
data signals. The simulated data signals were connected to
the inputs of the FM multiplexer VCO’s. Electro-Mechanical
Research, Inc. (EMR) model 4150 FM subcarrier discriminators
£
2-2
w're used to demodulate the composite FM multiplex signals
to recover the multiplexed data signals.
An EMR model 4059 detranslator was used to translate
the IRIG channels 7A through 21A signals down to three groups
of 1A through 5A signals. The detranslator develops
translating frequencies of 120 kHz, 160 kHz, and 200 kHz
from an external 240 kHz reference signal. The 240 kHz
reference frequency obtained from the multiplexer was
supplied to the detranslator during the tape recording tests
to facilitate tape speed compensation.
The data signals, recovered at the output of the dis-
criminators, were measured using an oscilloscope, a voltmeter,
and a total harmonic distortion analyzer to determine the
degree of data signal degradation which is caused by the
multiplexing, recording, and transmission process. Phase
delay measurements were also made to determine how accurately
different data signals can be time-correlated when the
signals are multiplexed.
2-3
3.0 DISCUSSION
3.1 VCO PERFORMANCE TESTS
The FM multiplexer, the simulated data signals, and
the test equipment were connected as shown in figure 3-1.
Static data signal noise, dynamic data signal distortion,
channel-to-channel phase error, and crosstalk measurements
were made with the multiplexer output connected directly to
the discriminators.
3.1.1 Static Noise Tests
Peak-to-peak noise at the outputs of the subcarrier
discriminators was measured with static data signals of 0,
2.5, and 5.0 applied to the VCO signal inputs. These meas-
urements were made using VCO deviation ratios of 1 and 2.
The measurements expressed as percentages of full scale are
given in table II.
The maximum peak-to-peak noise on the received data
signals measured for a data signal deviation ratio of 1
was 1.3 percent of full scale for an input signal of 2.5 Vdc
(VCO center frequency); the maximum peak-to-peak noise
measured with input signals of 0 Vdc (VCO low bandedge)
and 5.0 Vdc (VCO high bandedge) was 3.9 percent.
The value of 3.9 percent was measured for channel 6A
with the VCO frequency set to high bandedge (5.0 Vdc data
signal). The noise measured for channel 7A with the
same input signal was 3.5 percent of full scale. The
3-1
Figure 3-1. - Block diagram of laboratory 21 channel constant
bandwidth multiplexer evaluation tests.
TABLE II. - -.TATIC DATA SIGNAL NOISE, pk-pk PERCENT OF FULL SCALE
vco
Channel
0 Vdc
2.5 Vdc
5.0 Vdc
0 Vdc
2.5 Vdc
5.0 Vdc
Noise, % FS pk-pk
•—I
n
O'
Q
DR= 2
1A
1.8
1.3
1.7
.5
.4
.5
2A
1.8
1.3
1.7
.4
.4
.5
3A
1.5
.8
1.4
.4
. 3
.3
4 A
1.8
1.1
1.8
.4
.4
.6
5A
1.6
1 . 7
1.7
.3
.4
.5
6A
1.3
.9
3.9
.5
.4
.4
7 A
1.3
.9
3.5
.5
. 3
. 4
8A
1.5
1.0
1.7
.3
.4
.6
9A
2.0
.9
1.7
.4
.4
.4
10A
1 . 8
.0
1.8
.4
.4
.5
1 1 A
1 . 3
.9
1.4
. 3
. 3
.4
12A
1.6
.9
1.6
.4
.3
.4
13A
1 .5
i.i
1 . 8
.5
. 4
.6
14A
2.6
.9
2.8
.4
.3
.4
15A
1.2
. 8
1 .3
. 3
. 3
...
. 3
16A
1.5
1 .0
1 .4
.3
. 3
. 4
1 7 A
.9
.6
1 . 3
. 3
I
2
i
1 8 A
.9
.6
I .0
. 2
->
19A
i
.8
- -
2.4
. 3
. 4
. S
20A
.6
.9
T
■>
2 1 A
1.0
.6
.8
. 3
*>
. 3
3 -?
relatively high noise levels for these two channels are
caused by mutual interference between the two VCO signals.
Channel 7A is obtained by translating a 56 kHz VCO signal
to obtain a signal which has a frequency of 64 kHz. The
translation causes a 180 degree change in the deviation
sensitivity of the resulting signal. When a 5.0 Vdc signal
is applied to both channel 6A and channel 7A, the channel
6A VCO frequency is at high bandedge and the channel 7A
VCO frequency, obtained by translation, is at low bandedge.
The frequency separation between the two VCO's is minimum
for this condition so t>at maximum crosstalk occurs.
The noise on the data signals measured for channels 14A
(120 kHz) and 19A (160 kHz) with 0 Vdc and 5.0 Vdc data
signals were also relatively high. With the input signal
set to 5.0 Vdc, 2.8 percent was measured on channel 14A and
2.4 percent was measured on channel 19A. The higher noise
levels on these channels is caused by feed-through of the
120 kHz translation signal from the 120 kHz translator, and
feed-through of the 160 kHz translation signal from the
160 kHz translator. The noise levels measured are not
considered excessive but do show the necessity of suppressing
the translation signal at the outputs of the translators.
The maximum peak-to-peak noise on the received data
signals measured at a deviation ratio of 2 was 0.4 percent
for an input signal of 2.5 Vdc; the maximum peak-to-peak
noise measured with input signals of 0 and 5.0 Vdc was
0.6 percent. The use of a deviation ratio of 2 eliminated
the data signal, degradation which occurred on channels 6A ,
7A , 14A, and 19A when a data signal deviation ratio of 1
was used.
3-4
3.1«2 Dynamic Data Signal,
Harmonic Distortion
Sine wave data signals were applied to the VCO's.
Recovered data signal total harmonic distortion was measured
at the subcarrier discriminator outputs. The measurements
were made using VCO deviation ratios of 1 and 2.
The results of the measurements are given in table III.
The maximum total harmonic distortion measured for a
data signal deviation ratio of 2 was 0.65 percent. The
maximum total harmonic distortion measured for a data signal
deviation ratio of 1 was 3.0 percent.
The distortion analyzer filters out the data signal
fundamental component and provides a measure of the remaining
content of the data signal. This measurement gives an
indication of noise and crosstalk contained in the received
data signal.
3.1.3 Phase Error, Channel-to-Channel
A single sine wave data signal was connected in parallel
to the inputs of all VCO's. The difference in phase between
the recovered data signals was measured at the output of
the subcarrier discriminators for data signal frequencies
of 2.0, 1.0, and 0,5 kHz. Measurements were made using 2 kHz
low pass filters (DR=1) and 1 kHz low pass filters (DR=2).
The measured values of phase errors are given in table IV.
3-5
TABLE III. - DYNAMIC DATA SIGNAL, PERCENT TOTAL HARMONIC
DISTORTION, SYSTEM BASELINE TEST
vco
Channel
Data Signal
Freq, Hz
Data
VCO
Channel
Data Signal
Freq, Hz
Data
% THD
% THD
DR=1
DR=2
1A
2000
1.85
1A
1000
0.34
2A
1900
2.40
2A
900
0.33
3A
1800
2.65
3A
800
0.58
4A
1750
2.55
4A
750
0.52
5A
2000
2.60
5A
1000
0.49
6A
1900
2.25
6A
900
0.33
7A
1800
2.75
7A
800
0.32
8A
1900
2.65
. j
8A
900
0.58
9A
2000
2.30
9A
1000
0.37
10A
.
1750
10A
750
0.58
11A
1800
2.65
11A
600
0.28
12A
1750
2.40
12A
750
0.32
13A
1800
3.00
13A
800
0.56
14A
1900
2.30
14A
ra
ISA
2000
2.65
ISA
1000
0.4 7
16A
1750
2.70
16A
750
0.38
17A
2000
2.50
17A
1000
■El
18A
1750
18A
19A
1800
■S3
19A
800
0.05
20A
1900
■S3
20A
900
0. >1
2 1A
2000
1.85
21A
1000
n.:4
3-6
TABLE IV. - DYNAMIC DATA SIGNAL, CHANNEL-TO- CHANNEL
PHASE ERROR, SYSTEM BASELINE TEST
vco
Channel
Freq 2.0 kHz,
degrees
Freq 1,0 kHz,
degrees
Freq 1,0 kHz,
degrees
DR s I
DR= 2
1A-2A
-14.5
-6.9
-8.4
5.6
2A-3A
-7.3
-2.8
-11.8
-2.5
3A-4A
+ 2.0
-1.2
+4.6 0 !
4A-5A
-11.5
-3.8
-8.7
-1.5
5A-6A
+ 7.5
+ 2.4
-2.7
-.7
6A-7A
+ 5.5
+ 2.8
+ 14.1
+ 4.3
7 A- 8A
- 3.7
-1.7
- 7.7
-3.0
8A-9A
+ 2.2
+ 1.4
-5.1
-.3
9A-10A
+6.0
+ 3.0
+ 18.4
+ 3.6
10A-11A
+ 9.0
+;.s
-9.0
0
11A-12A
-6.5
-5.8
-3.3
-3.0
12A-13A
-12.5
-4.2
+ . 6
-.5
13A-14A
+ 2.5
+ 1.6
+ 9.3
+ 1.9
14A-15A
+ 6.0
+ 3.3
-2.4
+ 1.0
15A-16A
+ 10.5
+ 4.1
+ 13.2
+ 2.4
16A-17A
-18.1
-7.7
-12.2
-4.5
17A-18A
-4.5
-2.1
-8.2
-3.2
18A-19A
+ 2.7
+ 1.8
-5.0
-.1
19A-20A
+ 5.7
+ 2.8
+ 18.3
+ 3.6
20A-21A
+9.0
+ 4.0
-9.1
- 2
1A-7A
-18.7
-10.0
-13.2
-5.5
1A-12A
-12.5
-7.0
-10.2
-4.1
1A-17A
-19.0
-10.1
-18.0
-5.6
3
The maximum phase shift measured between channels is
as follows:
DR*1
Data Signal
Maximum Phase
Frequency (kHz)
Shift (degrees)
2.0
-19 (Ch 1A to Ch 17A)
1.0
-10.1 (Ch 1A to Ch 17A)
DR=2
1.0
+18.4 (Ch 9A to Ch 10A)
0.5
-5.6 (Ch 1A to Ch 2A and
Ch 1A to Ch 17A)
3.1 .4 Crosstalk, Channel-to -Channel
A 5 V pk-pk sine wave data signal was applied in turn
to channels 6A, 1;A, 16A and 21A. A 2.5 Vdc data signal was
applied to the remaining VCO’s. The peak-to-peak noise on
the received data signals obtained from the remaining VCC's
was measured to determine the amount of crosstalk caused b-
the sine wave signals. The crosstalk measurements were
performed for a data signal deviation ratio of 1 with a
sine wave signal frequency of 2.0 kHz. The results of the
crosstalk measurements are given in table V.
The test results indicate that most of vhe crosstalk
occurs on the VCO’s adjacent to the VCO which is modulated
by the sine wave signal. The worst case crosstalk increased
the noise on the unmodulated VCO's from 0.9 to 2.8 percent
peak-to-peak.
3-8
TABLE V. - CHANNEL-TO- CHANNEL CROSSTALK TEST
Crosstalk
Condition
Noise, 1 FS pk-pk
DR-1
Channel
Basic
Noise
6A
11A
16A
21 A
1A
1.3
1.2
1.2
1.2
1.2
2A
SB
1.0
1.1
1.3
«.«
3A
mm
.8
.9
.9
.8
4A
1.1
1.3
1.2
1.2
1.2
SA
HO
2.8
1.0
.9
.9
6A
.9
Signal
1.0
1.0
.9
7 A
. 9
2.8
1.3
1.3
1.3
8A
1.0
1.0
1.1
1.0
.9
9 A
.9
1.0
1.0
1.0
1.0
10A
■9
1.4
2 8
1.3
1.3
HA
.8
Signal
1.1
1.0
1 2 A
_
Si
.9
2.6
1.0
_ . ;
1.0
13A
1.1
1.8
1.5
mm
1.7
14 A
.9
.9
1.2
1.0
1 SA
.8
.8
- - - - -|
.8
■
.9
IbA
1.0
1.3
1.3
Signal
1.3
1 7 A
. 6
.7
* /
2.4
.7
18A
.6
.8
.6
7
.8
19A
.8
.9
.9
.9
.9
20 A
.0
.6
.6
.6
2.2
2 i A
7
.6
.6
Signal
•9
The crosstalk measurements were made with the unmodu-
lated VCO’s set at their center frequencies. The crosstalk
on an unmodulated VCO will increase as the frequency of the
VCO is moved toward the frequency of an adjacent VCO.
3.2 RECORDING TESTS
The output of the FM multiplexer was recorded on an
Ampex FR 1300 magnetic tape recorder at a recorder speed of
60 inches per second, using direct record-playback electronics.
The recorded tape was played back with the reproduced signal
connected to the subcarrier discriminators to determine the
degradation in data signal quality caused by the tape record-
ing process. The FM multiplexer, simulated data signals, and
test equipment were connected as shown in figure 3-1.
The recorder normal record level was set to 1.0 Vrms,
i.e., a 1.0 Vrms sine wave signal produces 1.0 percent third
harmonic distortion on the tape. Each of the VCO levels was
set to a nominal value of 70 mVrms; the 240 kHz tape speed
reference signal was set to a nominal value of 140 mVrms.
The tape speed reference signal was set 6 dB higher than
the VCO signals to ensure that a relatively clean signal
would be available for providing tape speed and tape flutter
compensation for the recorded data signals during tape play-
back. The VCO and reference signal levels were chosen such
that the composite recorded signal would have a nominal
peak-to-peak value of 2.8 volts when the signal was observed
using an oscilloscope.
3-10
Prior to recording the FM multiplexer signal, recorder
slot noise measurements were made relative to the normal
record level. A wave analyzer with 3.0 kHz filter band-
width was used to make the measurements. The measured signal-
to-noise ratios are listed in table VI. The measured noise
was used to obtain an indication of the noise in a 1.0 kHz
and a 2.0 kHz bandwidth over the frequency range of the
recorder. These values are also listed in table VI. The
data signal-to-noise ratio will depend on the tape noise
levels; the results obtained 5or the tests reported here can
be used to predict the performance of a different recorder
only if the signal-to-noise characteristics of the recorders
are the same.
3.2.1 Static Data Signal Noise
The output of the FM multiplexer was recorded with
0, 2.5, and 5.0 Vdc data signals applied to the VCO's. The
recorded tape was played back, and the reproduced signal was
connected to the subcarrier discriminators. The peak-to-
peak noise on the recovered data signals was measured.
Measurements were made using deviation ratios of 1 and 2.
Measured values expressed as percentages of full scale are
given in table VII.
With a data signal deviation ratio of 1.0, the maximum
peak-to-peak noise for a 2.5 Vdc data signal was 3.5 percent;
the maximum peak-to-peak noise was 6.0 percent for 0.0 and
5.0 Vdc data signals.
3-11
TABLE VI. - TAPE RECORDER SLOT NOISE DATA
Frequency ,
(kHz)
Measured SNR,
3.0 kHz BW
Calculated SNR
2.0 kHz BW
1.0 kHz BW
10
57
58.8
61.8
20
67
68.8
71.8
40
67
68.8
71.8
80
67
68.8
71.8
100
65
68.8
69.8
175
64
65.8
68.8
240
63
64.8
67.8
3-12
TABLE VII. - STATIC DATA SIGNAL NOISE, pk-pk PERCENT OF
FULL SCALE, RECORDED DATA TEST
vco
Channel
0 Vdc
2.5 Vdc j 5.0 Vdc
0 Vdc
2.5 Vdc
5.0 Vdc
Noise, % FS pk-pk
DR=1
DR=2
1A
4.0
2.8
3.5
■a
1.0
1.8
2A
3.5
2.5
3.5
i.i
1.0
1.1
3A
3.5
mm
3.5
■B
1.0
1.2
4A
4.0
2.5
4.0
1.3
1.3
1.2
5A
4.0
2.5
4.0
1.3
mm
1.3
6A
4.0
2.8
6.0
■n
1.4
1.5
7A
4.5
2.8
6.0
m
1.3
1.5
8A
4.5
3.0
5.0
1.5
1.3
1.5
9A
5.0
3.0
5.0
1.5
1.3
1.5
10A
5.0
3.0
5.0
1.5
1.3
1.6
11A
5.0
3.0
5.0
1.5
1.4
1.5
12A
S.O
3.0
6.0
1.5
1.5
1.7
13A
5.0
3.5
5.5
m
1.5
1.8
14A
6.0
3.3
6.0
1.6
1.5
1.8
15A
i
6.0
warn
5.5
■a
1.5
1.7
16A
6.0
3.5
5.5
1.7
1.5
1.7
17A
5.5
mam
6.0
. . . i
1.7
1.6
1.8
18A
5.5
warn
6.0
1.6
1.5
1.7
19A
6.0
6.0
■B
mm
1.8
20A
6 . C
3.2
6.0
1.8
1.5
1.7
21A
6.0
3.2
6.0
1.7
1.6
1.7
3-13
With a data signal deviation ratio of 2.0, the maximum
peak-to-peak noise for a 2.5 Vdc data signal was 1.6 percent;
the maximum peak-to-peak noise for 0.0 and 5.0 Vdc data
signals was 1.8 percent.
3.2.2 Static Data Signal Noise With
Induced Tape Recorder Flutter
Tape recorder flutter levels of 2.42 and 4.5 percent
were induced by placing adhesive tape on the recorder
capstan. Static data signals were recorded and played back
as described in section 3.2.1. The measured values of noise
on the data signals, expressed as percentages of full scale,
are given in table VIII.
A comparison of the test results listed in table VIII
and those listed in table VII (no induced flutter) shows
that the induced flutter increases the peak-to-peak noise
on the received data signals. With 2.42 percent flutter and
a deviation ratio of 2, the worst case noise was increased
from 1.8 percent to 2.3 percent; with a deviation ratio of
one, the worst case noise increased from 6.0 percent to
7.0 percent. With 4.5 percent flutter and a deviation
ratio of 2, the worst case noise increased from 1.8 percent
to 2.5 percent; with a deviation ratio of 1, the worst
case noise increased from 6.0 percent to 8.0 percent.
3.2.3 Dynamic Data Signal
Harmonic Distortion
The output of the FM multiplexer was recorded with
sine wave data signals applied to the VCO's. The recorded
3-14
TABLt VIII. - PLAYBACK STATIC DATA SIGNAL NOISE, pk-pk PERCENT OF FULL SCALE,
hITIi TAPE RECORDED FLUTTER, RECORDED DATA TEST
\co
channel
0 Vdc
2.5 Vdc 1 5.0 Vdc
1
0 Vdc
2.5 Vdc
5.0 Vdc
Noise, * FS pk-pk
t)R*l
DR* 2
2 . 42t Flutter j
IA
4.0
:.s
4.0
1.3
1.0
1.3
:a
■a
:.s
4.0
B9
1.0
1.2
3A
i
2.4
4.5
1.3
1.0
1.3
4\
■
2.^
4.5
1.2
1.4
SA
IQQI
2.7
4.5
1. 1
1.2
1.4
b\
S.O
2.8
6.5
i.-
1.4
1.5
'4
'.0
IB
1.4
1.7
Kill
3.0
5.5
r m
1.4
1.5
5.S
3.0
5.5
-
IB
1.3
1.6
10 \
5.5
5.3
3.5
IB
1 L\
5.5
Li^
3 . 5
12A
5.5
6.0
l.t»
1.3
2.0
r>\
6.0
MTM
6.0
J
i.o
1 . 5
2.0
14 \
6.0
3.5
■MUM
1 5
1.8
ISA
JpUB
6.o ! :.o
i
1.3
1.8
ll>\
rm
■
—Iff 1
- -■
1 . 3
i:\
('.5
3. *
(,5 i
1.6
13\
■a
KgB
6.o , :.o
1.6
1.8
19 \
2.5
1*'
1 9
■a
3 . ~
c>.d
..5
1.6
2.0
mm
■
5.7
6.' 1
1.5
1.5
VCO
Channel
5.0 Vdc
0 Vdc
5.0 Vdc
Noise, \ FS pk-pk
DR*1
ui=:
4.5* Flutter |
14
4.0
2.8
4.0
2.0
1.2
1.6
2A
2.b
4.0
1.2
1.3
3A
2.7
4.0
1.4
1.3
1.4
44
BB
2.8
4.0
1.4
1.4
54
3.0
4.0
1.6
1 4
1.5
64
BB
igy
1.7
1.8
—
1.8
1.8
| 84
6.0
3.5
l.“
l.S
—
S.O
2.0
l."
t>.0
3.6
5.0
2.0
1.7
1.8
114
6.0
3.6
5.0
2.0
1.6
1.7
12A
7.0
5.8
5.5
2.4
1.8
13A
7.0
4.0
mi
BB
2.0
2 . 5
14A
8.0
4.0
6.0
, .
1.8
154
".0
1 1
4.0
5.5
2.4
1.8
1.8
L
16 \
7.5 ' 40
5.5
2.4
1.8
17\
8.0
L 4 ' n
5.5
2.5
2.0
2.0
18A
~.5
—
5.5
B
5.0
1
Ki-ai
B
B
204
♦
B
5.5
2.4
1.7
’•‘i
21A
|
5.5
2.4
>•-
1.8
5
i
i
i
tape was played back with the reproduced signal connected
to the subcarrier discriminators. The total harmonic
distortion of the recovered data signals was measured.
Measurements were made using deviation ratios of 1 and 2.
The measured values are given in table IX.
The maximum distortion measured at a data signal devia-
tion ratio of 2 was 0.86 percent; the maximum distortion
measured at a deviation ratio of 1 was 3.3 percent. The
measured values provide an indication of the crosstalk and
tape noise contained in the data signals.
3.2.4 Dynamic Data Signal Harmonic Distortion
With Induced Tape Recorder Flutter
Tape recorder flutter levels of 2.42 and 4.5 percent
were induced by placing adhesive tape on the recorder
capstan. Sine wave data signals were recorded and played
back as described in section 3.2.3. The measured values of
total harmonic distortion are given in table X.
The values listed in table X compared with those in
table IX (no induced flutter) show that the induced flutter
causes a significant increase in the data signal distortion.
With 2.42 percent flutter, the maximum distortion for a
deviation ratio of 2 was 1.95 percent; the maximum distor-
tion at a deviation ratio of 1 was 4.1 percent.
With 4.5 percent induced flutter, the maximum distor-
tion for a deviation ratio of 2 was 4.1 percent; the
maximum distortion at a deviation ratio of 1 was 5.5 percent.
3-16
TABLE IX. - PLAYBACK DYNAMIC DATA SIGNAL, PERCENT TOTAL
HARMONIC DISTORTION, RECORDED DATA TEST
vco
Channel
Data
Freq, kHz
Data
vco
Channel
Data
Freq, kHz
Data
% THD
% THD
DR=1
DR=2
1A
2.0
1A
1.0
.56
2A
1.9
2.6
2A
.9
.49
3A
1.8
2.9
3A
.8
.69
4A
1.75
2.8
4A
.75
.66
5A
2.0
2.8
5A
1.0
.66
6A
1.9
2.55
6A
.9
.55
7A
1.8
2.9
Ik
.8
.53
8A
1.9
2.95
8A
.9
.71
9A
2.0
2.6
9A
1.0
.61
10A
1.75
3.0
10A
.75
.74
11A
1.8
3.0
11A
.8
.55
12A
1.75
2.8
12A
.75
.58
13A
1.8
3.3
13A
.8
.73
14A
1.9
2.7
14A
.9
.70
15A
2.0
3.0
15A
1.0
.72
16A
1.75
3.1
16A
.75
.61
17A
2.0
2.9
17A
1.0
.58
18A
1.75
3.3
18A
.75
.76
19A
1.8
3.0
19A
.8
.86
20A
1.9
3.0
20A
. Q
.76
21A
2.0
2.45
21A
1.0
.60
3-17
1‘AiiLL X. - PLAT BACK DTNAM1C DATA SIGNAL, PLRCLN1 TOTAL HARMON I G DISTORT ION,
hi Tit T APfr RECORDED FLUTT1R, RECORDLD DATA TI ST
.8
The tape recorder flutter causes frequency modulation
of the data signals as well as frequency modulation of the
VCO signals. The frequency modulation of the data signal
cannot be corrected by the tape speed compensation equipment
available. The distortion measured is essentially a measure
of the sidebands around the data signals which are produced
by the frequency modulation.
3.3 TRANSMITTED TESTS
The output of the FM multiplexer was used to frequency
modulate a S-band rf transmitter. The transmitter output
was connected through attenuators to a S-band FM receiver.
Adjustable attenuators were used to allow control of the
received power levels. The received FM multiplexer signal
was connected to the subcarrier discriminators to determine
the degradation in data signal quality caused by the trans-
mission process.
The FM multiplexer, simulated data signals, and test
equipment were connected as shown in figure 3-1.
The levels of the channel 10A through channel 21A VCO's
were set to produce a transmitter FM modulation index of 0.7.
The .^vels of channels 1A through 9A were set to produce a
minimum transmitter deviation of 61 kHz per channel to reduce
interference on these channels caused by the higher frequency
VCO's. The resulting peak transmitter deviation produced
by the composite signal was 1657 kHz. The FM receiver i.f.
3-19
bandwidth used was 3.3 MHz. The overall signal-to-noise ratio
for each VCO channel is obtained from the following equation.
F 2 B
SNR = 10 log 3/4 (DR) 2 + SNR D dB
F M B D R
where Fp is the transmitter frequency deviation produced by
the VCO signal , F^ is the VCO frequency, DR is the VCO devia-
tion ratio, Bjp is the receiver i.f. bandwidth. Bp is the
data signal low pass filter bandwidth, and SNR R is the
signal-to-noise ratio in the receiver i.f. section.
For a data signal deviation ratio of 2, the calculated
minimum data signal-to-noise ratio is as follows:
SNR - 10 log 3/4 (0.7) 2 (2) 2 + SNR R
* 36.8 + SNR R dB
For a data signal deviation ratio of 1, the calculated
minimum SNR is
SNR = 10 log 3/4 (0 . 7) 2 (l) 2 pp + SNR R
= 27.8 •• SNR R dB
The tests were performed at received power levels of
-73, -83, and -86 dBm. Tests were attempted at a received
power level of -89 dBm; this power level results in a
calculated receiver i.f. section signal-to-noise ratio of
3-20
E
10 dB. However, frequent FM noise spikes occurred at the
output of the data signal low pass filter at a received
power level of -89 dBm. When the power level was increased
to -86 dBm, the spikes became relatively infrequent and the
received data signals were considered to be usable.
The calculated data signal- to-noise ratios (rms-to-rms)
for the test received power levels are as follows:
Calculated SNR, dB
keceived power (dBm) DR=1 DR=2
-73
53.8
62.8
-83
43.2
57.8
-86
40.8
49.8
The value of -73 dBm is estimated to be the minimum
level which will be received from the Shuttle vehicle at
a slant range of 5 degrees. The use of a 10-watt trans-
mitter is assumed. This power level includes a factor to
account for the differences in system noise temperatures
between the test receiver and the receiver which would be
used to receive the signal from the Shuttle vehicle.
3.3.1 Static Data Signal Noise
The peak-to-peak noise on the recovered data signals
was measured at the outputs of the subcarrer discriminators
with 0, 2.5, and 5 Vdc data signals applied to the VCO's.
The measurements were made with 'eceived rf power levels of
-73, -83 and -86 dBm, and with VCO deviation ratios of 1
and 2. The measured values are given in table XI.
3-21
*v**n **"*®
TABLh XI. - STATIC DATA SIGNAL NO 1st, pk-pk I’l.RCbNT OT Ft! LI CALB
vco
Channe 1
0 VUc
warn
5.0 Vdc
Noise, 5
rs pk-pk
DR-1
DR*
rf Level * >73 dBm J
IA
4.5
2.0
4.5
1.0
.8
1.0
2A
4.5
2.5
4.5
1.2
3A
4.0
1.7
'.0
■Bi
.8
4A
4.5
2.5
4.5
.8
.9
1.2
SA
3.5
1.6
4.0
.6
.6
.8
6A
3.5
1.6
6.0
.8
.6
.7
7A
3.0
1.3
|
.8
.6
.8
8A
ma
.9
9A
.6
10A
5.0
iTs
3.5
|
.9
11 A
3.0
1.6
3.0
.6
.6
.6
12A
2.5
1.7
3.5
.6
.5
.6
13A
2.5
1.5
tj
CO
.6
. 5
. Q
14A
7.0
1.5
7.0
. 8
.5
t n
15A
■ ■ ■ H
2.0
1.5
3.0
.4
.4
r-7
1 6 \
:.o
1.1
1 .8
. 4
.4
.6
17\
l.S
1.0
1.8
.4 1 .4
.5
1 8 \
1 .s
i
2.0
. 4
. J
.4
liM
:.o
1.0
.4
.6
_ : "_i •» .
L_V
• 4
. 3
. 4
:i \
T ~
•* i 1 - J
■ ' i
. 4
VCO
Channel
0 Vdc j 2.5 Vdc *
3.0 Vdc
0 Vdc
2.5 V
.♦disc, - FS pk-pk
I)R=1
LrR-
rf Level * -83 dBm
1A
—
_ 2.0 __
4.0
.9
*
2A
S3
4.4
1.0
1.
3A
4.0
1.7
4.0
.7
*
4 A
—
4.5
2.8
4.4
. 8
•
5 A
'.0
1.8
3.5
.8
•
6A
4.0
1.8
.9
•
7A
3.5
1.8
5.5
L
.9
•
8 A
3.5
2.4
.9
•
9A
3.8
2.2
.9
3 0A
3.S
2.0
4.0
’ .0
n;
3.5
2.2
3.8
1.0
-
12A
3.4
2.0
oo
1 .0
1 3 A
♦ *>
- * -
3.8
1.0
14A
".5
2.3
o
OO
1.2
1 5 \
5.0
2.0
1
3.4
. Q
1 6 A
3 . 0 ! 2 . 0
3.0
. 8
i:a
2 . T l 1.8
3.0
. 9
1 8 \
2 . S ! 2.0
i -
1 .0
i - -
.6
19 \
5.: i :.p
l
1
3.5
.8
20a
:.s , i.s
3.0
. 6
2n
** ^
1.8
2. 8
. s
3-22
FQLDOUT FRA If
••“-■I St, pk-;;k 1'tRCLXT OF FULL SCALt , TR.WSM1TTU) OAT A Slitl.T
vco
Channel
0 Vdc
2.5 V
3.0 Vdc
0 Vdc
2.5 Vdc
5.0 Vdc
Noise, % FS pk-pk
DR =1
DR *2
rf Level * -86 dBm
1 A
4.0
2.0
4.0
1.0
.8
1.1
2 A
4.5
1.8
4.5
1.0
1.1
1.2
3 A
4.0
2.0
4.0
.8
.7
1.0
4 A
4.0
3.0
4.5
1.0
1.1
1.4
SA
3.5
2.0
4.0
.9
.8
1.1
6 A
3.5
2.4
6.0
1.1
1.0
1.1
7 A
2.4
6.0
1.2
1.0
1.2
8 A
4.0
2.8
4.0
1.2
1.2
1.3
9 A
4.0
2.8
4.0
1.2
3.1
1.2
10 A
4.0
2.8
4 5
1.3
1.2
1.5
11 A
4.0
2.8
4.0
1.3
1.2
1.4
12 A
4.0
3.0
4.5
1.3
1.2
1.4
13 A
5 . 5
2.8
4.0
1.3
1.2
1.5
14 A
8.0
-
2.6
8 . 5
t
1.4
1.2
1.5
15A
4.0
2.8
4.0
1.2
1.1
1.4
16 A
2.7
4.0
1.2
1.1
1.3
17A
3.5
■a
1.2
1.2 1
i
1.2
18A
3.5
4.0
1.2
1.1 '
i
1.2
m
4.0
WBM
4 . S
1.2
1.1
1.3
20 A
Wmm
warn
3. 5
1.2
1.1
1.2
21A
3.5
2.6
3.5
1.2
1.1
1.1
3-22
The signal- to-noise equations given in section 3.3
show that the FM transmitter deviation produced by each of
the VCO signals should be proportional to the frequency of
the VCO in order to obtain equal signal-to-noise ratios for
each of the VCO’s. When the VCO signal levels are set to
produce transmitter deviation which is proportional to the
VCO frequency, the lower frequency VCO’s signal levels must
be set to relatively low values and are subject to inter-
ference from intermodulation signals which may be produced
by the higher frequency VCO's. When this occurs, it may
be necessary to set the lower frequency VCO levels to a
minimum value.
The FM transmitter used provided a frequency deviation
sensitivity of 12.2 mVrms per kHz. In order to provide a
reasonable transmitter FM modulation index of 0.7 per VCO,
it was necessary to set the level of the highest frequency
VCO at 10 mVrms. If a constant FM modulation index per VCO
was used, the level of the channel 1A VCO would be 0.92 mVrms.
It was necessary to increase the minimum VCO level to
5.0 mVrms in order to reduce the data signal noise levels
to the values listed in table XI.
The VCO signal output levels for channels 1A through
9A were set to 5»0 mVrms. The VCO signal levels for chan-
nels 1CA through 21A were set to produce a transmitter FM
modulation index of 0.7 per VCO. When the VCO’s are
operated at low signal levels, the signals are subject to
interference from extraneous signals, such as the trans-
lating signals which are present in the multiplexer. The
120 kHz translation signal caused 7.0 percent of full scale
3-23
peak-to-peak noise on the channel 14A (120 kHz center
frequency VCO when the data signal was set to 0 Vdc or
5.0 Vdc. Reduced data signal noise levels for the lower
frequency VCO’s could be obtained if a transmitter were
used which had a lower deviation sensitivity.
3.3.2 Dynamic Data Signal Distortion
Sine wave data signals were applied to the VCO’s. The
total harmonic distortion of the recovered data signals was
measured. Measurements were made with a received power
level of -73 dBm with VCO deviation ratios of 1 and 2.
The measured values are given in table XII. The measured
values indicate the noise and crosstalk content of the data
signals.
3-24
TABLE XII. - DYNAMIC DATA SIGNAL, PERCENT TOTAL HARMONIC
DISTORTION, TRANSMITTED DATA TEST
VCO
Channel
Data
Freq, kHz
-73 dBm
1 THD
DR-1
1A
2.0
2.0
2A
1.9
2.75
3A
1.8
2.8
4A
1.75
2.85
5A
2.0
2.65
6A
1.9
mm
7A
1.8
2.8
8A
1.9
2.75
9A
2.0
2.35
10A
1.75
3.0
11A
1.8
2.65
12A
1.75
2 . S
13A
1.8
3.0
14A
1.9
warn
15A
2.0
2.6
mm
1.75
2.75
17 A
2.0
mm
ISA
1.75
2.9
19 A
1.8
2.6
20A
1.9
mm
21A
2 . C
1.85
VCO
Channel
Data
Freq, kHz
-73 dBm
t THD
DR- 2
1A
1.0
.44
2A
.9
.48
3A
.8
.64
4A
.75
.58
5A
1.0
.55
* 6A
_ _
.9
.47
7A
.8
.43
8A
.9
.66
9A
1.0
.51
10A
.75
.71
11A
.£
.45
12A
.75
.48
13A
.8
.64
14A
.9
.57
15A
1.0
.57
16A
.75
.45
17 A
1.0
.44
18A
.75
.64
19A
.8
.48
20A
.9
.58
21A
1.0
.41
3-25
4.0 CONCLUSIONS
The test results indicate that the 21 channel IRIG-A
VCO’s can be used to satisfactorily multiplex 21 data signals
which have frequency ranges of dc to 2 kHz. The results
indicate that the quality of the received data signals depends
on the data signal deviation ratio used, i.e., the frequency
range of the signals which are to be multiplexed. The VCO
channels were tested with deviation ratios of 1 (dc to 2 kHz
data signal frequency range) and 2 (dc to 1 kHz data signal
frequency range). The quality of the received data signals
is considerably better when a deviation ratio of 2 is used.
The narrower data signal low pass filter associated with a
deviation ratio of 2 decreases the noise contained with the
data signal and reduces the interference caused by channel -
to-channel crosstalk. When some data signal degradation can
be tolerated, a data signal deviation ratio of 1 can be used
to double the frequency range capacity of the multiplexer.
4.1 VCO PERFORMANCE
The tests were performed with the multiplexer output
connected directly to the discriminators to obtain baseline
performance data, so that any performance degradation caused
by the recording and transmission processes could be
determined. The maximum data signal noise measured with
the FM multiplexer connected directly to the discriminators
was 3.9 percent peak- to-peak. The maximum value was meas-
ured for VCO channel 6A with a 5.0 Vdc input signal and a
data signal deviation ratio of 1.
4-1
The noise levels measured for channels 6A and 7A with
a 5.0 Vdc data signal applied to both VCO's is caused by
mutual crosstalk between the VCO's. Since the channel 7A
VCO signal is obtained by translation, a 5.0 Vdc input signal
produces a low bandedge frequency, while a 5.0 Vdc input
signal applied to channel 6A produces a high bandedge
frequency. The two VCO signal frequencies are as near as
possible to each other and a maximum crosstalk condition
exists when a 5.0 Vdc data signal is applied simultaneously
to both VCO's.
The data signal noise levels measured for channels 14A
(120 kHz) and 19A (160 kHz) at a deviation ratio of 1 were
higher than the noise measured on channels other than chan-
nels 6A and 7A (ref. table II). The noise measured on these
channels was caused by interference produced by the 120 kHz
and 160 kHz multiplexer translators. The noise levels are
not considered excessive but do show the possibility that
the interference could be worse on these channels if the
suppression of the translating frequency at the translator
output is inadequate.
The data signal distortion measurements and the cross-
talk measurements made at a data signal deviation ratio of
1 show that crosstalk between the channels can be expected.
The data signal distortion measurements were made with all
VCO's simultaneously modulated by full scale sine wave data
signals. The data signal frequencies were made unequal so
that crosstalk signals could not be coherent with the data
signal on a particular VCO channel. The maximum data signal
4-2
distortion was 3.0 percent. This value was measured for
channels 13A and 18A at a deviation ratio of 1. The crosstalk
is inherent and can be reduced effectively only by increasing
the spacing between the VCO frequencies or by increasing the
deviation ratio. The maximum data signal distortion was
0.65 percent when the deviation ratio was increased to 2.
The channel- to- channel phase error tests were made by
applying a single signal to all the VCO's and by measuring
the phase difference oetween the signals at the discriminator
data signal low pass outputs. The maximum phase shift between
channels was 19 degrees for a data signal frequency of 2.0 kHz
the phase shift decreased in approximate proportion to the
signal frequency as the data signal frequency was decreased,
and was a maximum of 5.6 degrees at a data signal frequency
of 0.5 kHz. Phase shift calibration of the channels would
be required if the time correlation between data signals
must be more accurate than that which is indicated by the
measured phase errors .
4.2 RECORDING TESTS
Test results indicate that some degradation in data
signal quality will occur due to tape noise (ref. tables IX
through XII). However, the degradation is minimal and the
test results are considered to be satisfactory. The peak-to-
peak noise measured with dc data signals was a maximum cf
1.8 percent when a data signal deviation ratio of 2 was used;
the peak-to-peak noise was a maximum of 6.0 percent when a
deviation ratio of 1 was used. The total harmonic distor-
tion measured with sine wave signals on all VCO channels was
4-3
a maximum of 0.86 percent when a data signal deviation ratio
of 2 was used; the maximum distortion was 3.3 percent when
a deviation ratio of 1 was used.
The tests which were performed with induced tape speed
flutter levels of 2.42 and 4.5 percent show that the flutter
noise can be reduced effectively by the tape speed compensa-
tion equipment. The 4.5 percent flutter level increased the
peak-to-peak noise from a maximum of 6.0 percent (no recorder
flutter) to a maximum of 8.0 percent when a data signal
deviation ratio of 1 was used, and from a maximum of 1.8 per-
cent (no recorder flutter) to a maximum of 2.5 percent when
a deviation of 2 was used. A significant increase in data
distortion was found when flutter was induced. The recorded
sine wave data signals are frequency modulated by the
recorder flutter. The distortion measured : increased
because of the sidebands around the data signals which are
caused by the frequency modulation. Tape speed compensation
equipment which would eliminate frequency modulation of the
data signals is not available. The distortion measured at
a deviation ratio of 1 increased from 3.3 percent (no flutter)
to a maximum of 5.5 percent when 4.5 percent flutter was
induced.
4.3 RF TRANSMISSION TESTS
The test results show that the 21 IRIG-A VCO channels
can be transmitted satisfactorily using a S-band rf trans-
mitter, and that standard FM signal- to-noise ratio calcula-
tions can be made to predict the data signal signal -to-noise
ratio that will be experienced for a particular receiver
rf power level.
4-4
For a received power level of -73 dBm, (estimated
minimum value which would be received from the Shuttle
vehicle), the maximum peak-to-peak noise level was 1.2 per-
cent for a deviation ratio of 2 and 7.0 percent for a devia-
tion ratio of 1. Additional tests were performed with the
received rf level decreased to levels which are near the
receiver threshold. Although data obtained at the lower
rf levels are degraded by the receiver noise, the degradation
is not severe, and the data obtained with the received rf
level set to -86 dBm is considered to be acceptable.
While the test results are considered satisfactory, it
was necessary to set the VCO output signals at relatively
low levels to obtain reasonable transmitter frequency devia-
tion, and the signals were subject to interference from
extraneous signals, such as those generated in the multi-
plexer translators. The test results could be improved
if a transmitter with a lower frequency deviation sensitivity
were used. This would allow the VCO signal levels to be
raised so that the signals would be less susceptible to
interference.
4-5
APPENDIX A
TASK 60 TEST PROCEDURE
EVALUATION OF TWENTY -ONE "A" CHANNEL
CONSTANT BANDWIDTH FM MULTIPLEXER
A- 1
TASK 60 TEST PROCEDURE
EVALUATION OF TWENTY -ONE "A" CHANNEL
CONSTANT BANDWIDTH FM MULTIPLEXER
APPROVAL :
Astrionics Programs Office
Astrionics Programs Office
February 1974
EE-5-73-103
TASK 60 TEST PROCEDURE
EVALUATION OF TWENTY-ONE "A" CHANNEL
CONSTANT BANDWIDTH FM MULTIPLEXER
PREPARED BY
C . E. Coe _
Asttionics
ogmzant
Projects
Engineer
Section
APPROVED BY
,7
t22Zad&
J
W J .Shan n a han , Supervisor
istrionics Projects Section
L. R. Watkins, General Department Manager
Tracking and Communications Systems Department
Prepared By
Lockheed Electronics Company, Inc.
For
Astrionics Programs Office
Tracking and Communications Development Division
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
LYNDON B. JOHNSON SPACE CENTER
HOUSTON, TEXAS
February 1974
l
LEC- 1801
Shuttle
CONTENTS
Section Page
1.0 INTRODUCTION 1-1
2.0 STATIC STIMULATION NOISE TESTS 2-1
2.1 CALIBRATION 2-1
2.2 RECORDER SETUP 2-1
2.3 SYSTEM BASELINE 2-2
2.4 RECORDED DATA 2-4
2.4.1 Recording Procedure 2-4
2.5 TRANSMITTED DATA 2-6
2.5.1 Preliminary Steps 2-6
2.5.2 Transmitting Procedure 2-8
3.0 DYNAMIC STIMULATION DISTORTION TESTS 3-1
3.1 PRELIMINARY STEPS 3-1
3.2 CALIBRATION 3-4
3.3 SYSTEM BASELINE DATA 3-4
3.3.1 Baseline Data 3-4
3.3.2 Interchannel Crosstalk 3-5
3.3.3 Interchannel Phase 3-5
3.4 RECORDED DATA 3-6
3.5 TRANSMITTED DATA 3-6
3.5.1 Preliminary Steps 3-6
3.5.2 Transmitting Procedures 3-8
ii
Appendix Page
A DATA SHEETS A-l
i ii
FIGURES
Figure Page
1*1 DFI-CBW "A" channel modulation package
configuration 1-2
2-1 Static test baseline 2-3
2-2 Recorded data test 2-5
2- 3 Transmitted data test 2-6
3- 1 Dynamic test baseline 3-2
3-2 Recorded data test 3-3
3-3 Transmitted data test 3-7
iv
TASK 60 TEST PROCEDURE
EVALUATION OF TWENTY -ONE "A" 2HANNEL
CONSTAND BANDWIDTH FM MULTIPLEXER
1.0 INTRODUCTION
The tests described in this procedure are for evaluating
a 21-channel constant bandwidth (CBW) FM Multiplexer. They are
conducted to provide typical data and operating characteris-
tics of the translated system of "A" channels, which are
located at center frequencies of 16 to 176 kHz.
Sonex, Inc. voltage controlled oscillators (VCO's), and mixer
amplifiers are mounted remotely and are cable connected to
the summing chassis which contains the reference oscillator,
translators and final mixer. (See figure 1-1.) The VCO
modulation package is contained as part of the task 60 bread-
boar' 4 . External test equipment includes the data signal
simulators or stimuli to the VCO's. The FR 1300 simulates
an onboard recorder configuration; the wideband (2272.5 MHz,
10 watt) transmitter, also on the task 60 breadboard, provides
the rf transmission mode for the CBW. Evaluation test equip-
ment is primarily contained in the development flight instru-
mentation (DFI breadboard ground support equipment (GSE) and
a CBW detranslator/discriminator rack assembly.
The static tests at center and bandedge frequencies
provide noise data for worst case conditions. Dynamic
simulation of the VCO's to both bandedges gives a represen-
tation of total harmonic distortion. This procedure treats
the two tests independently. Both recorded and transmitted
data will be taken for the two basic types of tests.
1-1
2
Figure l-l.-DFI-CBW "A" channel modulation package configuration.
Previous CBW modulation tests (Ref. EE-5-73-501, Task 60
Initial CBW Modulation System Test Report) indicated that
adequate signal quality could be obtained with a transmitter
deviation of 0.7, a total peak deviation of 504 kHz for the
12 channel, six translated system. Therefore, this deviation
factor will be used in these tests for comparison.
Both static and dynamic tests will be oerformed using
an instrumentation recorder, intermediate . dwidth (300 Hz
to 300 kHz), and an rf receiver (3300 kHz It. , .
Tests will be conducted at modulation indexes of 1
and 2, where:
Mod index 1—2 kHz low pass filters (LPF) are installed
in data discriminators.
Mod index 2—1 kHz filters are installed in data
discriminators .
The equipment list sheet should be maintained throughout
these tests. The test equipment and procedure may be modi-
fied at the discretion of the test conductor in order to
obtain the required data. Test configuration and signal
path data sheets are to be maintained to supplement the
procedural figures.
1-3
7.0 STATIC STIMULATION NOISE TEST
2.1 CALIBRATION
Basic Method .— Calibrate the oscilloscope and discrim-
inators so that 100 mV deflection on the oscilloscope will
indicate 1 percent. This is accomplished using the TM cali-
brator and adjusting each discriminator output for ±5 Vdc at
bandedges and 0 Vdc at center frequency.
Alternate Method .— Apply +2.5 Vdc stimulus to all VCO's
on the modulation package. Set the discriminators for 0 Vdc
as read on the oscilloscope. Vary stimulus to +5 Vdc and
adjust discriminator output for a +5 Vdc response as read
on the oscilloscope. Repeat, using 0 Vdc. Repeat these
steps as often as needed to establish a ±5 Vdc from bandedge
to bandedge as indicated on the oscilloscope. Perform
calibration on each discriminator to be used.
2.2 RECORDER SETUP
Using the Ampex FR1300 operations manual, ensure that
recorder direct- record/reproduce amplifiers are set up for
60 ips. Check record level by measuring the third harmonic
level with a wave analyzer. With a flutter meter, measure
the nominal recorder flutter characteristic. Perform a
frequency response ch ,'ck for these CBW test frequencies,
measure the signal-to-noise ratio, and record on data sheet
A-7. Perform tape and recorder slot noise measuiements per
data sheet instructions (A-7 and A-8).
2-1
2.3 SYSTEM BASELINE DATA
Performance check of VCO's and mixers shall have been
performed previously with the special 21 -channel chassis
prior to these tests. CBW test system and support equip-
ment baseline noise is measured and recorded according to
the following steps. See figure 2-1.
1. Apply +2.5 Vdc stimulus to all VCO's by setting
the Epsco Power Supply to +2.5 Vdc.
2. Set the composite package output using a wave
analyzer. Monitor the mixer amplifier output,
and adjust each data VCO for 0.070 Vrms and the
240 kHz reference oscillator component for 0.140 Vrms.
Ensure that the 2 kHz filters are in the discrim-
inators. Record data on sheets A- 11 through A- 14.
3. Using the Tektronix oscilloscope, monitor the
discriminator output and record the peak-to-peak
noise levels in percent for each channel. Repeat
test with Epsco set at +5 Vdc (upper bandedge)
and 0 Vdc (lower bandedge) .
4. Monitor the bandpass filter of each discriminator
using the Beckman counter, and record frequencies
for each of the following conditions:
0 Vdc stimulus
+5 Vdc stimulus
+2.5 Vdc stimulus
NOTE: Wideband amplifier (HP 467A) is required
to raise signal levels to the triggering
level of counter.
2-2
3
Figure 2-1. - Static test baseline.
5. Repeat the above with 1 kHz filters for MI * 2;
a repeat of step 4 is not required.
2 . 4 RECORDED DATA
Configure the Ampex FR1300 and test equipment as des-
cribed in figure 2-2.
2.4.1 Recording Procedure
NOTE: Mod package set per baseline test.
1. Set stimulus (Epsco) for +2.5 Vdc.
2. Verify that VCO and reference levels are per
baseline test, and that 1 kHz filters are
installed in the data discriminators.
3. Read and record composite signal amplitude
prerecording using HP 3400 for true rms and
oscilloscope for peak-to-peak volts.
4. Record data with stimulus (Epsco) set for
0 Vdc, +2.5 Vdc and +5 Vdc. Record suffi-
cient data at each point to allow for making
measurements of percent noise and frequency
for each VCO on playback.
5. Play back recording, making measurement of
percent noise, frequency of each VCO and
reference, composite signal (rms) and peak-
to-peak. Record on data sheet A-15.
6. Induce approximately 2.5 percent flutter on
tape recorder.
2-4
figure 2 - 2 . - Recorded data test.
NOTE: Flutter shall be induced by adding
tape to the capstan and repeating
measurements of tape recorder
flutter until conditions of steps 6
and 9 are met.
Measure percent flutter on tape recorder,
test frequency 50 kHz, bandpass 2 to 5 kHz,
FK switch at 2o.
Repeat steps 4 and 5. Record on data sheet A- 16
Induce approximately 5 percent flutter on
tape recorder. Measure per step 7.
Repeat steps 4 and 5. Record on data sheet A- 17
Change discriminator filters to 2 kHz and
play back the recordings made in steps 5,
8, and 10. Record the data on sheets A- 18,
19 and 20.
2.5 TRANSMITTED DATA
2.5.1 Preliminary Steps
Connect equipment as described in figure 2-3.
Set up modulation package preemphasis
according to the deviation schedule
(appendix sheet A- 10). Measure and record
the VCO levels, the composite rms , and
peak-to-peak voltage at the transmitter
input. Disable the mod package 240 kHz
reference frequency.
Figure 2-3. - Transmitted data test.
3. Set up TMR74 receiver for 3300 kHz IF bandwidth
and 250 kHz video bandwidth.
4. Configure rf components per appendix sheet A-9.
Apply power to the Conic transmitter and
measure the power level at the 20 dB power
attenuator output. Reconnect per figure 2-3
and measure power at the cable end to the
receiver, with both R^ and set tc zero.
Subtract these two numbers and add 20 dB for
the fixed path loss. Measure power level at
the -30 dB sampling port of the first coupler.
To this measurement add 50 dB, thus giving
the transmitter power. Perform calculations
for variable attenuator settings for the
total received power per the rf setup and
calibration data sheet A-9.
5. Complete the cabling between the Conic trans-
mitter, the rf attenuator, coupler, and
receiver. Apply modulation to the transmitter,
dial maximum attenuation, then apply trans-
mitter power. Readjust rf attenuator
corresponding to the first rf level on the
appendix data sheet A-9.
6. Ascertain that 2 kHz filters are installed
(MI * 1).
2.5.2 Transmitting Procedure
1. Read and record percent noise and VCO fre-
quency for each channel, with rf level set
for -73 dBm. Record data on sheets A-21, 22 and 2
2-8
2. Reset attenuators corresponding to -83 dBm.
Repeat step 1, except for frequency measurement.
3. Reset attenuators corresponding to -86 dBm.
4. Repeat step 1, except for frequency measurement.
5. Install discriminator 1 kHz filters (MI * 2).
6. Repeat steps 1 through 4. Record data on sheets
A-24 , 25 and 26.
2-9
3.0 DYNAMIC STIMULATION DISTORTION TESTS
3.1 PRELIMINARY STEPS
The equipment shall be configured as shown in figure 3-1.
Signal generators (oscillators) are set to dynamically stimu-
late the CBW subcarrier oscillators according to the
following :
CBW dynamic test signals
1. Discriminator MI = 1 (2 kHz Filters)
CH 1A, 5A, 9A, 15A , 17A, 21A = 2.0 kHz
CH 2A, 6A, 8A, 14A, 20A = 1.9 kHz
CH 3A, 7A, 11A , 13A, 19A =1.8 kHz
CH 4A, 10A, 12A , 16A, 18A = 1.75 kHz
2. Discriminator MI = 2 (1 kHz Filters)
CH 1A, 5A> 9A, 15A, 17A, 21A = 1.0 kHz
CH 2A , 6A, 8A, 14A, 20A = 0.9 kHz
CH 3A, 7A, 11A, 13A , 19A = 0.8 kHz
CH 4A , 10A, 12A, 16A, 18A = 0,75 kHz
3.2 CALIBRATION
Reference the tape recorder, transmitter, receiver and
rf path setups in the previous static tests. No changes are
required. VCO output amplitudes must be checked with only
the +2.5 Vdc stimulus applied to their inputs.
3-1
3*2
Figure 5-1. - Dynamic test baseline.
3.3 SYSTEM BASELINE DATA
Using the DFI breadboard and GSE, set up the equipment
as shown in figure 3-2. External oscillators will be required
as well as a harmonic distortion analyzer.
3.3.1 Baseline Data
1. Set up bias power supply for (+) 2.5 Vdc, into
common VCO input for VCO center frequency
adjustment. Record data on sheet A- 27.
2. With the wave analyzer, measure and reset VCO
levels to 70 mV and reference to 140 mV.
3. Connect bias supply to the oscillators as
shown; enable the 240 kHz reference oscillator.
4. Set oscillators to the above frequencies for
MI » 1 with dial accuracy; set output levels
to 5 V pk-pk, using the oscilloscope.
Reference paragraph 3.1 for frequencies and
distribution.
5. Ensure that discriminators contain 2 kHz filters.
6. Read and recced on the data sheet the total
harmonic distortion (THD) for each of the dis-
criminator channel outputs. Record on data
sheet A-27.
7. Change discriminator filters to 1 kHz and test
frequencies for MI * 2; repeat steps 6 and 7.
Record on data sheet A-27.
3-3
3-f|
Figure 3- 2 . - Recorded data test.
3.3.2 Interchannel Crosstalk
Obtain basic noise data from sheet A- 13, and use in
obtaining the crosstalk component.
1. Stimulate channel 6A with 2 kHz, 5 V pk-pk,
and measure the percent noise on each of the
remaining channel outputs. Record on data
sheet A- 32.
2. Stimulate, in turn, channel 11A, 16A, and 21A;
and repeat measurements as per step 1. Record
data on sheet A- 32.
3.3.3 Interchannel Phase
Assuring setup of VCO outputs for recording levels,
simultaneously apply a test signal to two channels, per
sheet A-33. The test signal amplitude shall be 5 V peak-to-
peak. With a phase meter measure the adjacent channels’
phase lead or lag. Record data on sheet A-33.
1. Perform the measurement with test signal
at 2 kHz and with 2 kHz LPF's.
2. Change signal frequency to 1 kHz, aid repeat.
3. Change to 1 kHz LPF’s and repeat.
4. Reduce signal to 500 Hz and repeat measurement.
3-5
3 . 4 RECORDED DATA
Change equipment setup to include the Ampex FR1300
between the mod package and the detranslator discriminators,
as in the static tests previously run. See figure 2-1.
1. Read and record the composite signal amplitude,
volts peak-to-peak, and volts rms.
2. Record data with oscillators set to 5 V pk-pk,
and record sufficient data to allow time for
THD measurements on each channel.
3. Play back recording, measuring the THD for
each channel through 1 kHz discriminator
filters (MI = 2). Record data on sheet A-28.
4. Rewind tape and change filters to 2 kHz and
reset oscillator frequencies. Then play back
recording, measuring the individual channel's
THD.
5. Use same equipment as in the paragraphs above.
Add tape to the recorder capstan to provide
~2 percent flutter. Repeat steps 1 through 4.
Record data on sheet A-29.
6. Repeat step 1 above, but change tape to provide
»5 percent flutter. Record data on sheet A-30.
3.5 TRANSMITTED DATA
3.5.1 Preliminary Steps
Configure CBW system per figure 3-3, and perform checks
to assure rf path setup per section 2.5.1. Disable the
240 kHz reference oscillator.
3-6
3
Figure 3-3. - Transmitted data test.
3.5.2 Transmitting Procedure
1. With the rf level set for -73 dBm, read and
record the test signal frequencies and
measure the total harmonic distortion (THD)
for each channel. The test signals are set
up for MI = 1 data. Record data on sheet A- 31
2. Install discriminator 1 kHz filters; repeat
step 1 with the MI * 2 test signal frequencies
3-8
APPENDIX A
DATA SHEETS
A- 1
CONTENTS
Page
Equipment list A- 4
FR1300 record/playback setup A- 7
Tape recorder setup — slot noise A-8
RF setup and calibration A-9
RF deviation schedule A- 10
SC frequency — baseline, MI = 1 A-il
SC frequency — baseline, MI = 2 A- 12
Percent noise — baseline, MI = 1 A- 13
Percent noise — baseline, MI = 2 A- 14
Percent noise — recorded, MI = 1 A- 15
Percent noise — recorded, MI = 1, 2.5$ flutter. . . . A-16
Percent noise — recorded, MI = 1 , 5.0% flutter. . . . A-17
Percent noise — recorded, MI = 2 A- 18
Percent noise — recorded, MI = 2, 2.5% flutter. . . . A-19
Percent noise — recorded, MI = 2, 5.0% flutter. . . . A-20
Percent noise — transmitted, MI = 1 A-21
Percent noise — transmitted, MI = 2 A-24
Distortion — baseline A-27
Distortion — recorded A- 28
Distortion - recorded, 2.5% flutter A-29
Distortion - recorded, 5.0% flutter A-30
A- 2
Distortion — transmitted A-31
Crosstalk - transmitted A- 32
Interchannel phase A-33
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