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CONFIDENTIAL
RESEARCH DEPARTMENT
Mutual Interference between Naval Radar
and VHF FM Broadcasting in
Band II— B. B.C. and A.S.R.E. Tests
Report No. K-101
[1955/1]
THE BRITISH BROADCASTING CORPORATION
ENGINEERING DIVISION
RESEARCH DEPARTMENT
MUTUAL INTERFERENCE BETWEEN NAVAL RADAR
AND VHF FM BROADCASTING IN
BAND II — B.B.C, AND A.S.RoE, TESTS
Report No. K-iOi
[1955/!]
R,A« Rowden, B> Sc (Eng. ) f D.I.C,,, A.M. I.E. E.
D.G. Beadle, B.Sc. (Eng. ), A.M. i.E.E. ^ 4o-jtLl/**u i
G.I. Ross ^r^ c, ^*^^_______
D.E. Susans - '
K.h. Green (W. Proctor Wilson)
Thi s a
sport
1 s
th
e property of
the
British
Broad
Basting
Corporation and
nay
not be
r eprodu
led
or di
solo sed to a
third j
arty
in
an;
form
il thout
the
written
pern]
ssi
on
of the
Corp oration •
Report No. K-101
MUTUAL INTERFERENCE BETWEEN" NAVAL RADAR
AND VHF FM BROADCASTING IN
BAND II — -B.B..C. AND A..S.R.E.. TESTS
Section Title Page
1 SUMMARY .
2 INTRODUCTION
GENERAL . . .
4 PROGRAMME OF TRIALS .
INTERPRETATION OP FIELD STRENGTH MEASUREMENTS .
6 INTERFERENCE WITH TYPE 281 RADAR FROM WROTHAM ....
INTERFERENCE WITH FM BROADCASTING FROM TYPE 281 RADAR
8 INTERFERENCE WITH FM BROADCASTING FROM TYPE 960 RADAR . 10
9 CONCLUSIONS ....... ................ 12
APPENDIX 14
CONFIDENTIAL
Report No. K-101
January 1955 [l955/l]
MUTUAL INTERFERENCE BETWEEN NAVAL RADAR
AND THE FM BROADCASTING IN
BAND II B.B.C. AND A. S.R.E. TESTS
1. SUMMARY.
Tests were carried out by the Admiralty Signal and Radar Establishment
and the B.B.C. Research Department to investigate the mutual interference likely to
arise from the co— channel operation of naval radar sets Type 281 and Type 960 with
YHF FM broadcasting stations,
Specific measurements and observations on land in the Brighton area and at
sea on board H.M.S. Boxer are described. It is concluded that perceptible inter-
ference would arise in coastal areas by the operation of the naval radar sets at sea
out to ranges from the coast of the order of 70 km and 180 km in the case of the
Type 281 and Type 960 sets respectively. The result of the tests on interference
with the operation of the Type 281 set from a high power YHF transmitter cannot be
regarded as conclusive as, for technical reasons, naval apparatus could not be
adjusted to work exactly on the same frequency channel as the "7HF FM transmitter.
Tests indicate quite definitely, however, that a serious degree of interference with
the radar may occur within ranges from a VHF FM transmitter of 250 km.
It is recommended that co-channel operation of the naval radar sets and
VHF FM broadcasting should, if possible, be avoided, at least in coastal waters.
2, INTRODUCTION.
This report describes some tests arranged jointly by the Admiralty Signal
and Radar Establishment and the B.B„C. Research Department to determine the extent of
the mutual interference between the B.B.C. FM transmitters in Band II and the naval
radar equipment working on shared frequencies within the band.
The sharing of some part of the frequency band 88-100 Mc/s between YHF
broadcasting and naval radar arose in the following manner.
A document known as Paper Number 85 of the Inter-Departmental Committee on
Post- War Planning shows that FM broadcasting in the United Kingdom has the exclusive
use of the frequency band 90*5 Mc/s to 95 Mc/s and that it shares the band 88 Mc/s to
90*5 Mc/s with the naval Type 281 set. The Paper further states that the naval
Type 281 set has been granted priority on the frequencies 88 ± 0*5 Mc/s and 90
±0*5 Mc/s. It is stated that the allocations are based on agreements reached by the
Inter-Departmental Committee before the Atlantic City Conference, but have been
adjusted to fit within the framework of the allocation table agreed at the conference
for the European Region. The European Broadcasting Conference (1952) provides for
the use of the entire 88-95 Mc/s band by the United Kingdom for FM stations and
assigns frequencies to particular stations.
3. GMERAIu
In June 1952 H.M. S. Swiftsure reported serious interference with her Type 281
radar from B.B.C, Wroth am EM transmissions. As a result of H. M.S. Swiftsure 's report,
trials were arranged between the B.B.C. and the Admiralty Signal and Radar Establishment
(A.S.R.E. ) to determine not only the nature and extent of the interference experienced
by Type 281 from Wrotham but also that which Type 281 would cause to the reception of
frequency modulated signals.
Prom the point of view of obtaining the maximum information about mutual
interference, it was considered desirable to operate the interfering sources as. near
to one another as possible and then to increase the distance between them and. note how
the interference and field strength varied. For this. reason the B.B.C. initially
suggested carrying out the tests with a shipborne Type 281 in the Thames Estuary, the
nearest sea point to Wrotham and one that offered a "straight course for 130 km or
more offshore in a N.W. direction. The ship allocated for the trials. was, however,
H.M.S, Boxer, a radar training unit which normally operates in the Isle of Wight
area, and, as she was to carry out her normal training programme in addition to the
A.S.R.E. /B.B.C. trials, the tests were of necessity carried out in this area.
A B.B.C. Research Department Report Ar-021 "Radar Pulse Interference"
gave the results of some preliminary work on the problem carried out in 1946 when
measurements were made on a naval radar transmitter at Chatham. The work now described
is a more complete investigation embracing subjective listening tests and the. effect
of the jamming of the naval radar by a high power YHP transmitter.
The Radio Branch of the Post Off ice Engineering Department was informed of
the tests and sent observers to one of the B.B.C. receiving sites and to H.M.S. Boxer.
4. PROGRAMME OP TRIALS.
Tests were initially plan Tied for two consecutive days, as follows:
First day
1. H.M.S. Boxer to steam from a point off Worthing on the continuation of
a straight line joining Wrotham and the B.B.C. shore site (see5below)
towards Cherbourg.
2. Measurements of the field strength of Wrotham on 91*4 Mc/s to be made
periodically on hoard.
3. The Type 281 radar set to he tuned to 91*4 Mc/s and adjusted for the
radiation of a peak effective power of 3*2 MW in the direction of
maximum aerial gain,
4. The interference from the Wrotham transmission to the Type 281 set
receiver display to be noted and, if possible, photographically
recorded,
5. B.B.C. observations to be made at Shoreham-on— Sea at a site effectively
at sea level.
Second day
1. H.M.S, Boxer to steam on course approximately the reciprocal of that
of the first day.
2. Field strength and interference measurements and observations to be
made on board as on the first day,
3. B.B.C. observations to be made at a high site on the South Downs near
Brighton (initially planned as Truleigh Hill but later changed to the
Dyke Golf Club House),
The tests originally planned for two days, as above, were conducted on
1st, 2nd and 3rd February, 1954.
The observations made at the B.B.C. site consisted of:
a. measurements of ~ the Wrotham field strength;
b. measurements of the field strength of the signals from
H.M.S. Boxer j
c. subjective assessment of the degree of interference to
the required programme from Wrotham.
A change in the programme was necessitated by a mis— match between the
Type 281 feeder and aerials on a frequency of 91' 4 Mc/s. This had caused the
Pyrotenax feeder to be damaged when an attempt was made to radiate a peak power of
3*2 MW. The trials were, therefore, carried out with a Type 281 transmitter unit
operating on a frequency of 90-3 Me/s and a reduced. ERP of 0*8 MW,
A second radar set, Type 960, a modern counterpart of the Type 281, also
radiated. during the trials. This set, though capable of operating at frequencies up
to 90 Mc/s, is not at present permitted to operate in the 88-90*5 Mc/s band. The
B.B.C, however, took advantage of the facilities offered by.A.S.R.B. and subjective
tests were carried out to determine its effect on FM broadcasting.
The measurement of the amplitude of the pulses of the two radar sets was
made with a modified Gee receiver fitted with anti- jamming circuits. A locally
generated pulse from a standard signal generator was coupled into the Gee receiver and
its width and amplitude adjusted until it was equal to that received from the radar
sets. With this arrangement, it was possible to measure the field strength of the
pulses when their amplitude was 35-40 dB below that of a eo-ehannel FM signal.
Further data of transmitting and receiving equipment, site and aerial heights
are given in the Appendix.
5. INTERPRETATION OP FIELD' STRMGTH : M1ASDE1H1NTS.
Before discussing details of the observations, the method of evaluating
the field strength measurements both on ship and shore is described, On account of
fading, it was. necessary to observe the field strength of Wrotham on H.M.B, Boxer for
a period of 1-2 minutes and note the mean value. This was done at least once every
fifteen minutes and on completion of each run the mean measured- value was related to
distance from Wroth am by reference to the ship's log.
Field strength measurements on board H.M.S. Boxer could only be made
conveniently at a height of 9'8 metres above -sea level, although the height of the
aerial system of the Type 281 radar set was 35 metres above sea level. It is,
therefore, necessary to make a correction to the measurements made at the lower height
in order to arrive at values for the field incident on the Type 281 set aerial. This
has been done on a linear height gain basis, the-' gain factor being 3'6, This. is
likely to be the true gain for all ranges where the ship is below the radio horizon
from the last diffracting ridge on the wave path from Wrotham (the South Downs) but
for closer ranges the linear height gain may not ; apply. Since the ranges at which
the interference effects -were observed extend well beyond this horizon, all the
figures given in this report for the field strength of Wrotham on H.M.S. Boxer include
the linear height gain. correction.
The receiving aerials at the shore sites were all at a height of 9*2 metres
above ground level, the value (30 ft) being the height above ground generally accepted
as the height of the average listener's outdoor aerial.
Fading was observed on the signals received from H.M.S. Boxer at a distance
exceeding 65 km. Allowance has, however, been made for this by a process of averaging.
..All measured field strengths of the Type 281 set have been corrected for
the normal power of 3*2 MW and the distances corresponding to various degrees of
interference from the Type 281 set have likewise been corrected.
6. INTERFERING! WITH TYPE 281 RADAR FROM WROTHAM.
As the Type 881 transmitter unit could not be tuned to Wrotham's frequency,
it was impossible to observe co— channel interference under normal working conditions
and recourse was made to tuning the receiver unit to 91' 4 Mc/s while the transmitter
unit radiated on 90*3 Me/s. In this mis- tuned condition no echoes appeared on the
receiver displays but the effect of the interference. could be observed on either
cathode ray tube trace, as the aerial rotated through 360°,
The effect of the FM signal on the display was as follows I
As the amplitude of the interference signal increased, the trace level rose
and the noise amplitude decreased. Further increase of the interference level caused
the datum line of the trace to limit and the. noise to invert. This condition was
observed when H.M.S. Boxer was 200 km from Wrotham and the Type 281 aerial was
pointing towards Wrotham; the corresponding field strength was 20/iV/m. Still
further increase of the field strength reduced the amplitude of the noise to zero and
the cathode ray tubes then gave a clean trace. This condition corresponded to a
field strength of 45/^V/m.
When the interfering field strength exceeded 400/xV/m, it was possible to
observe both the interference and echoes by tuning the receiver unit to apoint mid— way
between 90' 3 Mc/s and 91*4 Mc/s. In this condition, similar effects were noted to
those described above.
Table 1 summarises the result of the observations as the distance between
H.M.S, Boxer and Wrotham was progressively decreased.
TABLE 1
Summary of Subjective Tests on Type 281 Radar
with Wrotham as the Source of Interference
Distance from Approximate Field Interference
Wrotham km Strength fXl/m
200 20 Trace limiting over an arc
of 40 and noise inverted
175-185 45 Trace wiped clean over an
arc of 40
170-175 63 Weak interference on back
lobe in addition to above
165 80 Weak interference on side
lobes in addition to above
140 250 Saturation jamming on all
bearings except arc of 40
on each side
130 400 Saturation jamming on all
bearings
The table shows that when the ship was 200 km from Wrotham, the Type 281
set was inoperative over an arc of 40 , and at 130 km from Wrotham, the set was
completely inoperative on all bearings. These conditions correspond to field
strengths of 20/xV/m and 400/-t"V/m respectively.
The ground profile 'between the Wrotham transmitter and the course seawards
from a point off Worthing is not very favourable for TOF transmission owing to the
attenuation introduced through diffraction losses, by the South Downs which rise to a
height of about 700 ft. To indicate the ranges at which interference with the
Type 281 radar set may be experienced when the ground profile outwards from the
transmitter is more favourable Table 2 below has been prepared. Here the distance
ranges have been derived from theoretical propagation curves for propagation over
average terrain (F.C.C. data, U.S.A.) and apply to a 90 Mc/s transmitter with an
effective radiated power of 125 kW and height of aerial of 1000 ft above the surround-
ing terrain.
TABLE 2
Probable Range of Interference with Type 281 Radar
from Typical High Power "VHF FM Transmitting Site
Distance from FM Station
(ERP 125 kW, aerial height 1000 ft) Interference
km
250 Trace limiting and noise inverted
over an arc of 40
200 Trace wiped clean over an arc of 40
185 Weak interference on back lobe in
addition to above
176 Weak interference on side lobes in
addition to above
145 Saturation jamming on all bearings
except for 40 arc on each side
132 Saturation jamming on all bearings
Under abnormal tropospheric propagation conditions the above ranges may be
considerably increased and the operational use of the Type 281 set would be further
restricted.
The A. S.R.E. representative on board H.M.S. Boxer decided to conduct the
tests without the anti- jamming circuits of the Type 281 set connected, for the
following reasons:
i. Under the particular conditions of the tests (Wrotham and the
Type 281 set operating on different frequencies), it was
considered that the results would be so unrealistic as to be
misleading.
ii. Anti-jamming circuits severely restrict the operational use
of the equipment in a number of ways.
7. INTERFERENCE .WITH FM BROADCASTING PROM TYPE 881 RADAR.
Subjective co— channel listening tests on Wrotham 's frequency with the
Type 281 set as the source of interference could. not he carried out as planned because,
as mentioned earlier in this report, the Type 281 set could not he tuned to 91" 4 Mc/s.
This difficulty was, however, overcome by tuning the FM receiver to the Type 281 set
pulse transmissions on 90-3 Me/s and injecting a locally generated frequency modulated
signal derived from a standard signal generator,
The signal generator was modulated with programme and the output level was
adjusted to correspond to the appropriate field strength at each receiving post, i.e.
0*5 mV/m at Shoreham and 9*0 mV/m at Dyke Golf Club House, It was thus possible to
observe the co— channel interference effect of Type 281 and, by retuning the local
signal generator, similar observations were made for Type 960 radiating on 86 Mc/s.
The field strength of both radar sets was measured periodically on a modified Gee
receiver at both receiving posts- The results of the observations on interference
from the Type 281 set are given in Table 3.
TABLE 3
Amplitude of
pulse relative
to that of the
FM carrier dB
Summary of Subjective Tests on an FM Signal with
Type 281 Radar as the Source of Interference
Distance from H.M.S. Boxer
km
Shoreham Dyke Golf Club House
(Wrotham 0*5 mY/m) (Wrotham 9-0 mY/m)
Degree of
Interference
-10
82
110
"Just perceptible"
when carrier
unmodulated
66
87
"Perceptible" when
carrier unmodulated
+ 10
+ 20
47
32
64
48
"Perceptible during
quiet passages in
programme
"Perceptible" on
programme of average
modulation level
+30
19
34
"Slightly disturbing"
on programme of
average modulation
level
+40*
11*
18*
"Disturbing" on
programme of average
modulation level
''These figures were obtained by extrapolation of tbe field strength/distance
curve for Type 38 1 and laboratory tests.
Before commencing on this table, it should be noted that the nearest H.M.S.
Boxer approached Shoreham was 15 km while the corresponding distance for Dyke Golf
Club House was 42 km. The data shown in the table for smaller distances were derived
by interpolation of the field strength/ distance curves for the Type 281 set and
laboratory tests subsequent to the trials.
The table shows that at Shoreham the degree of interference varied from
"just perceptible" when the carrier was unmodulated for H.M.S. Boxer 82 km distant, to
"disturbing" when she was 11 km distant. For the distances at which observations
were made the level of interference was never "very disturbing".
The distance between H.M.S. Boxer and Dyke Golf Club House for a given degree
of interference is considerably greater than that for the Shoreham site; this arises
from the fact that the field strength of the Type 281 set was greater, relative to
that of Wrotham, at Dyke Golf Club House than at Shoreham. This is readily seen from
Fig. 1 which makes direct comparison between the measured and theoretical field
strengths for both sites. The difference between the theoretical fields is 27 dB,
whereas the average difference between the measured fields is 34 dB. The discrepancy
between each measured field strength curve and the appropriate theoretical one is well
within the limits imposed by local site conditions.
The two receiving sites, one at sea level and one elevated on a high, clear
site, tend towards the extremes in elevation and it is considered that a typical
receiving site would lie somewhere between these limits. For this reason, a fifth
curve has been drawn on Fig. 1. This curve is for a field strength 10 dB greater
than the theoretical value for Shoreham, and, although arbitrary, it is considered to
be fairly representative of the field strength of the Type 281 set at a typical
coastal town.
Considering now the whole problem of interference from the Type 281 set in
more general terms, and taking the European Broadcasting Conference, Stockholm, 1952,
recommendation that a field of 0*25 mY/m should ,be protected for 99$ of the time,
Table 4 has been drawn up, based on the theoretical curves of Fig. 1. It gives the
distances between a shipborne Type 281 set and three receiving sites, one at sea level,
one . "typical", and one elevated, for various levels of interference. From the table
it will be seen that, due to the reduction in the protected field strength to 0*25 mY/m
compared with that of Wrotham, the distances at which a given level of interference
would be observed are considerably greater than those measured and shown in Table 3.
This is particularly so in the case of Dyke Golf Club House site, where the field
strength of Wrotham is 9'0 mY/m.
The use of theoretical rather than the measured field strengths is also
responsible for minor differences on both sites hut it is preferable to employ
"standard" field strengths when dealing with the general case.
In interpreting Tables 3 and 4, it should be borne in mind that when the
distance between the source of interference and the receiver exceeds 70-80 km,
abnormal tropospheric conditions would raise the level of interference above that
shown in the tables.
.000
500
100
50
10
500
100
50
10
-Mea
-Thee
5urec
>retic
alj
Dyke
Gol1
1 Club.
J
>
~ E
Thee
jretic
fpica
:al for ^s.
l" receiving
-site.
E
1.
SI
ioreh
fmeas
am tthec
.ured
retk
:al^"
\
Distar
ice kn
n.
1
10 20 30 40 50 60 70 80 90 100 I JO 120 130 140
Fig. I - Field strength of Types 281 and 960 radar transmitters
at B.B.C. receiving sites
10
TABLE 4
Interference between Type 881 and an FM Broadcasting
Service for three Receiver Sites
(FM Carrier Field Strength = 0- 25 mV/m)
Degree of Interference
Distance from Shipborne Type 881
km
Site at "Typical" Elevated
sea level site site
"Just perceptible"
when carrier
unmodulated
158
240
440*
"Perceptible"
when carrier
unmodulated
98
156
320*
"Perceptible"
during quiet
passages in programme
67
95
220
"Perceptible"
on programme of
average modulation level
46
69
132
"Slightly disturbing"
on programme of
average modulation level
30
46
86
"Disturbing"
16
89
60
These figures were obtained by extrapolation of the field strength/distance
curve for Type 28 1 and laboratory tests.
8. INTERFERENCE WITH FM BROADCASTING FROM TYPE 960 RADAR.
The Type 960 radar set is the modern counterpart of Type 881 and the only
significant difference in their transmission characteristics is that the Type 960 set
has a pulse repetition frequency of 850 c/s and the Type 881 set a pulse repetition
frequency of 100 c/s.
The interference tests using the Type 960 set as the source were carried out
in precisely the same way as those described for the Type 281 set and Table 5 is a
summary of these interference observations.
11
TABLE 5
Summary of Subjective Tests on an FM Signal with
Type 960 Radar as the Source of Interference
Amplitude of
pulse relative
to that of the
FM carrier dB
Distance from H.M. S.Boxer
km
Shoreham Dyke Golf Club House
(Wroth am 0-5 mV/m) (Wrotham 9-0 mV/m)
Degree of
Interference
-27
135
158
"Just perceptible"
when carrier
unmodulated
-13
87
110
"Just perceptible"
during quiet
passages
- 7
- 3
+ 3
+ 20
74
67
63
58
29
96
"Perceptible"
during quiet
passages
90
"Perceptible"
85
"Slightly dis
80
"Disturbing"
45
"Very disturb
Comparison between Tables 3 and 5 shows that the Type 960 set causes a
much higher level of interference than the Type 881 set. For example, when the field
strength equalled that of the wanted FM transmission, the level of interference was
"slightly disturbing", whereas the corresponding level for the Type 281 set was
"perceptible when the carrier is unmodulated". Further comparisons for the same
radar field strengths are "very disturbing" and "perceptible on programme of average
modulation level". These comparisons clearly show that, as expected, the set with
the higher pulse repetition frequency causes the higher interference level.
The measured field strength/distance curves for this set are almost exactly
the same as those for the Type 281 set shown in Fig. 1.
Both sets being of equal power, the same theoretical curves are used to
derive the distances for various levels of interference at three representative
receiver sites. The protected field strength considered is again 0*25 mV/m and the
results are given in Table 6.
12
TABLE 6
Interference between the Type 960 set and an FM Broadcasting
Service for three Receiver Sites
(FM Carrier Field Strength = 0' 25 mV/m)
Degree of Interference
Distance from Shipborne Type 960
km
Site at "Typical" Elevated
sea level site site
"Just perceptible"
when carrier
unmodulated
320
"Just perceptible"
during quiet passages
in musical programme
184
420*
"Perceptible
during quiet passages
in musical programme
138
218
406*
"Perceptible"
on programme of
average modulation level
116
182
350*
"Slightly disturbing"
on programme of
average modulation level
98
160
320
"Disturbing"
on programme of
average modulation level
87
136
290
"Very disturbing"
on programme of
average modulation level
46
70
132
*These figures were obtained by extrapolation of the field strength/distance
curve for the Type 28 1 set and laboratory tests.
9. CONCLUSIONS.
The experiments have shown that considerable mutual interference would
result if the naval radar sets are operated on shared frequency channels with VHP FM
broadcasting.
In particular, the interference suffered by the radar system might be such
as to render it inoperative in a ship within 200 km of a typical inland transmitter
13
site of the "high, power" type the B.B.C. proposes to use. In the exceptional case of
a high power EM transmitter on a high site near the coast, intolerable interference
might he suffered by the radar system out to ranges of 250 km.
The converse interference with FM broadcasting is not quite so serious
in terms of range hut the tests show that, in the case of a typical receiving loca-
tion, at average height above sea level and near the coast, interference graded as
"perceptible" or worse would be experienced when the shipborne radar was within 70 km
of the coast in the case of the Type 281 set, and within 180 km in the case of the
Type 960 set. In arriving at the above figures it is assumed that a second-class
service of 0'25 mV/m would be available to the listener.
Some of the results of the trials described in this report require qualifi-
cation since the co— channel tests were not carried out as originally planned. In
particular, it is considered that if the interference experienced by the Type 281 set
had been assessed in the presence of radar echoes it might not have been quite so
extensive as that indicated against a background of receiver noise. Furthermore,
co-channel tests would have provided data of a more detailed nature, showing the effect
of the interference on various aspects of the performance of the Type 281 set.
Likewise, tests with the Type 281 set using its anti— jamming circuits would have
provided data showing not only the extent to which they limit its performance in the
absence of interference but also that to which they enhance its performance in the
face of co- channel interference.
The tests to determine the extent to which an FM service would suffer from
co-channel operation of either the Type 281 or Type 960 set are not subject to the
same limitation, since, in this ease the co— channel conditions simulated by using a
locally generated FM signal are regarded as satisfactory.
The results of the tests provide strong support for the recommendation that,
if possible, co— channel working of FM broadcasting and the naval radar sets should be
avoided altogether or, if this is not possible, the use of the naval radar sets should
be restricted to sea areas at sufficient distance from the coast that there is no
possibility of mutual interference.
14
EQUIPMENT ON H.M.S. BOXER
APPENDIX
Transmission Characteristics
Pulse repetition frequency (c/s)
E.R.P. MW (max. )
Aerial height (ft)
Frequency (Mc/s)
Field Intensity Meter
RADAR UNITS
Type 281
Type 960
100
250
0-8
3-2
115
115
90-3
86
R.C.A. Type 301B (modified)
EQUIPMENT AT B.B.C. RECEIVING POST
C.W. Field Intensity Meter
For measurement of pulse amplitude
Oscilloscope
Standard signal generators
F.M. Receiver
Pulse Generator
A.F. Oscillators
SITE DATA
WROTH AM
Latitude
Longitude
National Grid Reference TO. (5D/594604
Site height (ft) aju.s.l. 720 (216 m)
Distance from Wrotham
(miles )
51° 19' 11 " N
00° 17' 20" E
R.C.A. Type 301B (modified)
Gee receiver Type 1355 (modified)
Type 27 (modified) R.F. Units
plus pre-amp.
Cossor Type 1035
Marconi Types TF.801A and TF.995
Fitton and Eddystone Type 770R
B.B.C.
B.B.C. and Ediswan Type R.666
SHORES AH
50° 49' 54" N
00° 14' 55" W
DYKE GOLF CLUB HOUSE
50° 52' 51" N
00° 12' 24" W
TO. (5D/234051 TO. (5D/251107
20 approx. (6m) 670 approx. (190 m)
41-5 (67 km)
38 (61 km)