PULSE WIDTH ( VICTIM) =0-83us

PRF ( VICTIM) =830.O00rrs
PULSE WIDTH( INTERFERER )=0 -50us
PRE CINTERFERER )=1200 -O0res

VIC. ANT. SWEEP RATE =13-O0rrn

INT. ANT. SWEEP RATE =15.50ren

WITH INITIAL REL~ AZIMUTH =350oe0
INT. BEARING =97oe0

MUTUAL ANT. GAIN THRESHGLO =-26 -30b8:

0

270

180

Fo sho oe &.
Aide 1 Weuricanes

of Leng Seach \SR-3 with
4 Interference

Figure E-s.


was found to be approximately 5.6 dB and is discussed in
Appendix A. Taking into account the additional attenuation
of the Long Beach antenna radiation backlobe and using the
measured FDR (Long Beach emission spectrum), propagation loss
and Long Beach antenna backlobe level, the measured INR is
-0.7 dB using Equation 3-1 as compared to the predicted INR
of 26.2 dB. An INR of approximately -0.7 @B would not cause
interference on the AN/CPN-4 PPI display. Predicted inter-
ference to the Los Alamitos AN/CPN-4 from the Long Beach
ASR-5 is shown in Figure E-2 using the PPI simulation model.
There was actually no observed interference from Long Beach
on the PPI display of the Los Alamitos AN/CPN-4 radar.

Ontario ASR-5. Interference was observed on the Los
Alamitos AN/CPN-4 PPI display from the Ontario ASR-5. Inter-
ference from the Ontario ASR-5 radar was not predicted since
the predicted INR was -4.6 dB for antenna coupling of the
mainbeam of the victim to backlobe of the interferer. The
emission spectrum of the Ontario ASR-5 radar is shown in
Figure B-12. The figure shows that the predicted FDR should
be within a few dB of the actual FDR. The measured propaga-
tion loss was found to be 184 dB (Table D-2) as compared to
183 predicted. Therefore, some other factor other than error
in the predicted FDR and propagation loss had to contribute
to the occurrence of interference from the Ontario ASR-5 radar
to the Los Alamitos AN/CPN-4 radar. Figures A-25 through A-27
show environmental antenna patterns of the Ontario ASR-5 radar
measured at Los Alamitos. The higher antenna sidelobe and
broadened beamwidth shown in these figures indicates the
presence of multipathing caused by diffraction and reflection
in the Chino Hills between the two radar sites. The broadened
beamwidth and higher sidelobe level of the Ontario antenna
pattern, as seen by the Los Alamitos radar, increased the
probability of equivalent mainbeam-to-mainbeam coupling.

INR measurements made using the 8580 receiver and tapping
off the AN/CPN-4 IF preamplifier output, yielded measured
INR's between 15 GB and 24 dB.

Norton AFB AN/MPN-13. Interference was observed on the
Los Alamitos radar from the Norton AFB AN/MPN-13 radar.
Interference from the Norton AFB AN/MPN-13 was not predicted
since the predicted INR was -8.9 dB. Since the Norton radar
is operating cochannel with the Los Alamitos AN/CPN-4 (Trans-
mitting frequency 2800 MHz, Figure B-11) the FDR rejection is
0 dB. The measured propagation loss was found to be 192°dB
(Table D-2) as compared to 198 dB predicted. Therefore, the
measured propagation loss was 6 dB less than predicted. How-
ever, the 6 dB less propagation loss does not account for the
occurrence of interference from the Norton AFB AN/MPN-13 radar.

E-5




PULSE WIDTH ( VICTIM) =0.83us

PRF ( VICTIM) =830.00rrs
PULSE WIDTH( INTERFERER )=2 -00us
PRF ( INTERFERER )=370 . OOres

VIC. ANT. SWEEP RATE =13-00Ren

INT. ANT. SWEEP RATE =0 -OOnen

WITH INITIAL REL. AZIMUTH =289o80
INT. BEARING =2300¢0

MUTUAL ANT. GAIN THRESHGLD =-0.90oe:

)

270

180

0.00 $3.00 eb .00

ny x
RRNGE I v Maur 12a LES

Fivure F-3. Simulated PPI Display of Long Beach ASR-5 with
San Pedro AN/FPS-90 Interference


Figure A-28 indicates that multipath phenomena also caused

the occurrence of interference from the Norton radar. The
broadening of Norton's antenna beam as seen by Los Alamitos
(Figure A-28), and the 6 dB lower than predicted propagation
loss, caused by mcuntain diffraction and reflection in the
Chino Hills, resulted in interference from the Norton AN/MPN-13
radar which was not predicted.

March AFB AN/MPN-13. Interference from the March AFB
BN/MPN-13 was also observed on the Los Alamitos AN/CPN-4 radar.
The predicted INR from the March radar was -17.6 dB. The
March radar also operates on approximately the same frequency
(Transmitter frequency 2800 MHz, Figure B-10) as the Norton
AN/MPN-13 radar and is also cochannel with the Los Alamitos
AN/CPN-4 radar. Propagation measurements from the March AFB
AN/MPN-13 could not be measured since the received power level
at the RSMS van 8580 receiver input was below the receiver
noise level. The RSMS van has approximately 25 dB less sensi-
tivity than the AN/CPN-4 radar due to a higher inherent noise
level and 11 dB less antenna gain. Interference from the
March AN/MPN-13 radar was identified by tapping off the
AN/CPN-4 IF preamplifier output and connecting it up to the
RSMS van 8580 receiver. Interfering signals from the Norton
AFB AN/MPN-13 were identified by requesting the Norton radar
to operate in their stagger mode (3 x 365 = 1095), and the
March radar with stagger off (1095 PRF). The AS-330 pulse
train separator was then used to differentiate between the
two radars.

LONG BEACH ASR-5 VICTIM RADAR MEASUREMENTS

The nominal characteristics of the Long Beach ASR-5 radar
are given in Table 4-2. Closed system measurements made on
the radar indicated that the nonsynchronous MDS INR was 6 GB
for normal channel and 5 dB for the MTI channel with the inte-
grator off. With the integrator on, the MDS INR was 6 GB for
the MTI channel. An INR of 10 GB would cause a steady level
of interference on both the normal and MTI channels even with
the integrator on. The receiver inherent noise level (N;) is
-106 dBm. 2

The ASR-5 radar site at Long Beach is a cluttered site,
and an ideal location for the RSMS van was very difficult to
find. The ASR-5 radar at Long Beach has an antenna height of
26 feet. The RSMS van dish height is only 14 feet. The RSMS
van cavity back spiral antennas mounted on a tower have the
capability of reaching a height of 25 feet. However, the
cavity back spiral antennas are not directional antennas

E-7


PULSE WIDTH ( VICTIM) =0.50us

PRF ( VICTIM) 2=1200.00rers
PULSE WIDTH(C INTERFERER )=0 -83us
PRF CINTERFERER )=830 .O0rrs

VIC. ANT. SWEEP RATE =15.50nen

INT. ANT. SWEEP RATE =13.00ren

WITH INITIAL REL. AZIMUTH =Ooee

INT. BEARING =277o80

MUTUAL ANT. GAIN THRESHOLD =-0.40os:

0

270

180

tb.co  th.oo 24.00 $b.00

oe
RANGE IN NAUTICAL MILES

Figure E-2. Simulated PPI Display of Los Alamitos AN/CPN-4
with Long Beach ASR-5 Interference

E-6


antenna) which would give an INR of 17 dB, and still cause
interference on the PPI display.

INR measurements made using the 8580 receiver and
tapping off the ASR-5 IF preamplifier output, yielded measured
INR's between +18 dB and +35 dB. During these detailed
measurements, the height finder did not nod at Long Beach.
Therefore, we did not measure an INR as high as +66 GB.
Predicted interference tc the Long Beach ASR-5 radar for
mainbeam of the victim coupling with the backlobe of the
height finder using the PPI simulation model is shown in
Figure E-3.

Burbank ASR-6. Interference was observed on the Long
Beach ASR-5 PPI display from the Burbank ASR-6 radar. The
interference from the Burbank radar appeared on the PPI dis-
play approximately 1 out of 5 scans, and covered approximately
a 3° sector at the bearing of the Burbank radar (320°). The
measured propagation loss from Burbank to Long Beach was found
to be 191 dB (Table D-2), and the predicted propagation loss
was 181 dB. kKcwever, the propagation loss measurements were
made with the RSMS van dish which was about 12 feet lower than
the ASR-5 antenna height. Because of foreground clutter,
measurements made with the dish may be a few dB low. Propa-
gation loss measurements from Burbank to Long Beach could not
be made with the cavity back spiral antenna to determine the
propagation loss as a function of antenna height because of
the inability to discriminate against the Long Beach ASR-5
emissions. The measured propagation loss from Long Beach to
Burbank was found to be 185 dB (Table D-2). This difference
in nonreciprocity is discussed in detail in Appendix D. An
estimate of the additional propagation loss due to the difference
in antenna height at Long Beach was 3 dB. Therefore, a good
estimate of the actual propagation loss from Burbank to Long
Beach would be 188 dB. An approximate FDR was taken from
Figure B-14, and found to be 27 dB. The average antenna back-
lobe level of the Burbank radar was found to be -11.9 dBi
(Table A-1). Using Equation 3-1 and the measured data, the
calculated INR would be -8.9 dB. One major factor contributing
to the big difference between measured and predicted INR levels
was the FDR factor. A frequency separation of 5 MHz (Long Beach
frequency 2780 MHz and Burbank frequency 2785 MHz). was used for
the INR prediction. Due to the fact that the ASR'S usually
do not operate at the edge of their 10 MHz band, the actual
frequency separation was 11 MHz (Long Beach frequency 2777 MHz
and Burbank frequency 2788 MHz). This made a difference in the
emission spectrum level of approximately 10 dB because of the
sharp fall-off of the emission spectrum for small AF. Measure-
ments indicate that the INR for mainbeam-to-backlobe coupling
was -8.9 dB which indicated that interference from the


APPENDIX E

DETAILED MEASUREMENTS

INTRODUCTION

Part of the Los Angeles and San Francisco area measurement
program involved making detailed measurements at several radar
sites. These measurements were made using the RSMS van instru-
mentation with the objective of determining what caused:

l. The absence of predicted interference,
2. The presence of unpredicted interference,

3. The interference having a different form on the PPI
scope than predicted.

These detailed measurements involved measuring:
1. Interferer emission spectrum,
2. Interferer antenna pattern at victim radar site,
3. Propagation loss between victim and interferer,
4. Victim radar antenna pattern.

A limited number of measurements were also made connecting the
RSMS 8580 receiver to the victim radar IF preamplifier output
with the victim radar transmitter turned off. This permitted
peak power measurements at the victim radar IF preamplifier
output, and positive identification of the interferer using
the AS-330 pulse train separator. The measured peak power
level at the IF preamplifier output was then converted to a

RF input level using a measured transfer function. A more ex-
panded discussion of the detailed measurement plan is given

in Appendix F.

The measured data referenced in this Appendix is contained
in Appendices A through D. The following is a discussion of the
detailed measurements conducted in the Los Angeles and San
Francisco areas.


PULSE WIDTH ( VICTIM) =0.83us

PRF ( VICTIM) =830.00res
PULSE WIOTHCINTERFERER )=0 .83us
PRF CINTERFERER J=1125 «00ers

VIC. ANT. SWEEP RATE =13.00ren

INT. ANT. SWEEP RATE =15-O00ren

WITH INITIAL REL- AZIMUTH =310o80
INT. BEARING =319oe0

MUTUAL ANT. GAIN THRESHOLD =12.0008

0

270 90

180

208 i. x
. fitee w'iGuricacniues

Figure E-4. Simulated PPI Display of Long Beach ASR-5 with
Burbank ASR-6 Interference

E-12


Burbank ASR-6 should not appear on the PPI display at Long
Beach. However, interference from the Burbank ASR-6 was
observed approximately 1 out of 5 scans. An explanation of
the possible cause of the interference is given in Appendix A.
Figure A-32 shows that a multipath phenomena was occurring due
to a mountain range between the two radars and a high mountain
range in back of the Burbank ASR-6 radar. INR measurements .
made using the 8580 receiver and tapping off the ASR-5 IF
preamplifier output, yielded measured INR's between +26 dB

and +35 dB. This indicates that the interference was occurring
when interfering signal levels were received due to the multi-
path phenomena. Figure E-4 shows the form of the predicted
interference using the PPI simulation program. .

Los Alamitos AN/CPN-4. Interference was observed on the
Long Beach ASR-5 PPI display from the Los Alamitos AN/CPN-4
radar. The interference from the Los Alamitos radar was very
infrequent and only appeared at the bearing of the Los
Alamitos radar (97°). Since the FDR is emission spectrum
limited, the FDR can be determined from Figure B-6. The FDR
(emission spectrum level at 2777 MHz) is approximately 38 dB.
The average backlobe level of the Los Alamitos antenna was
found to be -8.4 dB (Table A-1). The measured propagation
loss from Los Alamitos to Long Beach was 157 dB (Table D-2)
using the van cavity back spiral antennas at a height of 25
feet (approximate height of Long Beach ASR-5 antenna). When
the van dish was used at a height of 14 feet, the measured
propagation loss was 176 dB. Using the cavity back spiral
antennas and raising the tower from 14 feet to 25 feet, the
propagation loss decreased by 11 dB. The Long Beach ASR-5 radar
site was a cluttered site which caused the signal energy from
the Los Alamitos radar to be scattered. This was evident from
the smeared appearance of the interference on the Long Beach
ASR-5 PPI display. Because of this signal scattering phenomena
and antenna beamdwith difference associated with the measure-
Ment antennas and actual radar antenna, it is very difficult
to actually determine what the propagation loss was between
the two radars without using the radar antenna to measure
the propagation loss. The subject of propagation loss be-
tween these two antennas is discussed in more detail in
Appendix D. Another factor which may have contributed to the
absence of the frequency of predicted interference from the
Los Alamitos radar was additional attenuation of the Los Alamitos
antenna backlobe radiation due to foreground clutter. Also,
the Los Alamitos AN/CPN-4 radar had been realigned between the
time the emission spectrum was measured and the time the measure-
ments were made at Long Beach. The actual operating frequency of
the Los Alamitos AN/CPN-4 was changed from 2807 MHz to 2801 MHz.
This realignment could have also changed the emission spectrum
shape. Considering these factors, it is very difficult to assess



and reflections of the ASR-5 antenna platform and reflector
could cause erroneous propagation loss measurements.

The predicted interferers for the Long Beach ASR-5 radar
operating on the high channel were:

Interferer Victim
Radar Freq. (MHz) Freq. (MHz) INR
Sen Pedro
AN/FPS-90 2835 2777 2 Tel
Burbank ASR-6 2788 2777 12.8

Los Alamitos
AN/CPN-4 2801 2777 50.7

San Pedro BN/FES- 20. Interference from the San Pedro
AN/FPS-9 eight finding radar was observed on the PPI scope
of the ASR-5 at Long Beach. The interference varied from
covering a 40° sector of the PPI when the height finder's
vertically nodding antenna was pointed in azimuth at Long
Beach, to a 3° sector when the antenna was not pointed at
Long Beach. Because of the random scanning of the AN/FPS-90
antenna, it was difficult to measure propagation loss between
San Pedro and Long Beach. However, the RSMS van with a 20 4B
gain dish was used to monitor the power level received at
Long Beach from the height finder over a period of several
hours. A one-hour sample of this measured data, shown in Figure
D-5, indicates a maximum received peak power level of +4 dBm.
Since the 4 dBm level was also the maximum peak power measured
over a 12-hour period, it is likely that it occurred when the
San Pedro antenna was nodding at the Long Beach radar. Cor-
recting the +4 dBm level for the gain of the van dish gives
a peak power level at the ASR-5 antenna of -16 dBm (Pr). The
INR at the Long Beach ASR-5 IF output caused by the San Pedro
AN/FPS-90 can be determined by Equation E-l. It is shown in
Appendix C that the FDR is emission spectrum limited. The
measured emission spectrum of the San Pedro AN/FPS-90, as shown
in Figure B-19, indicates an FDR of approximately 51 dB at the
operating frequency (2777 MHz) of the Long Beach ASR-5 (the
predicted FDR was 61 dB, Figure C-13). Using Equation E-1l and
a mainbeam gain of +27 dBi (correcting for antenna tilt angle,
7 GB) and receiver noise level of -106 dBm, the calculated INR
for coupling from the San Pedro radar would be +66 GB indicates
why a majority of the PPI display was covered by interference
from the height finder when the AN/FPS-90 was nodding in the
direction of Long Beach. When the height finder was not nodding
in the direction of Long Beach, the INR should be approximately
49 dB less (mainbeam-to-median backlobe ratio of height finder

E-8


PULSE WIDTH ( VICTIM) <=0-50us

PRF ( VICTIM) =1200.OO0res
PULSE WIDTH( INTERFERER )=2 -0Ous
PRF CINTERFERER )=370 . 00rrs

VIC. ANT. SWEEP RATE =15.-50ren

INT. ANT. SWEEP RATE =0.-00ren

WITH INITIAL REL. AZIMUTH =174o80
INT. BEARING =244oe0

MUTUAL ANT. GAIN THRESHGLD =-2.30o8:

0

270

180

0.00 3-00 24.00 90.00

8.00 1b 00
RANGE IN NAUTICAL NILES

Figure E-l1. Simulated PPI Display of Los Alamitos AN/CPN-4
with San Pedro AN/FPS-99 Interference

L-4


Almaden AN/FPS-90. Interference from the Almaden AN/FPS-90
radar was observed on both channels of the Mountain View ASR-5
radar. The interference from the Almaden AN/FPS-90 radar covered
3° to 40° sectors of the victim radar PPI scope. For approxi-
mately twenty minutes, the Mountain View ASR-5 transmitter was
turned off, and the pulse train separator (AS-330) was used to
identify the PRF of signals processed by the radar receiver.
The pulse train separator locked on to the PRF (275) of the
Almaden radar. Due to the ability to coordinate with the ADC
personnel at Almaden, propagation path loss measurements from
the height finding radar were made by having the height finding
radar nod in the direction of Mountain View for a one-half hour
period. The measured propagation path loss from Almaden to
Mountain View was found to be 141 dB (Table D-3) which was
only two dB off from the predicted propagation loss of 143 dB.
Using the measured emission spectrum to determine the FDR
factor, Figure B-17 shows the emission spectrum to be down
36 dB from the fundamental frequency at 2758 MHz. The pre-
dicted FDR was 37 dB (Figure C-13). The backlobe antenna gain
of the Almaden AN/FPS-90 radar could not be measured. Using a
nominal antenna backlobe gain of -13 dBi for the Almaden radar,
the measured propagation loss and FDR, and the nominal charac-
teristics of the Mountain View ASR-5, the calculated INR is
35 dB using Equation 3-1. The actual predicted INR was 32 dB.

Predicted interference, using the PPI Simulation model, to
the Mountain View ASR-5 from the Almaden AN/FPS-90 is shown in
Figure 5-6. The actual observed interference varied from a 3°
to 40° wedge of interference on the victim PPI display. Several
runs of the PPI Simulation model need to be made to simulate
this dynamic nature of the interference on the victim PPI display.

Almaden AN/MPS-14. ADC personnel at Almaden alternate the
operation of the AN/MPS-14 and AN/FPS-90 on a monthly basis.
Because of this operating procedure verification of interference
from the Almaden AN/MPS-14 radar could not be made.

Mt. Tamalpais AN/FPS-90. Interference from the Mt. Tamalpais
AN/FPS-90 radar was observed on both channels of the Mountain View
ASR-5 radar. Positive identification of the interference was
made using the pulse train separator when the victim radar
transmitter was turned off. The interference from the Mt.
Tamalpais AN/FPS-90 appeared on the victim PPI display about
one out of every four scans as interference wedges of 3° to 30°.
Propagation measurements from the Mt. Tamalpais radar were also
made by having the height finding radar nod in the direction of
Mountain View for a one-half hour period. As mentioned in
Appendix D, the path from Mt. Tamalpais to Mountain View is
across the San Francisco Bay. The measurements showed a 14 dB
variation in the measured propagation loss from Mt. Tamalpais

E-15


Mather AFB AN/MPN-13. Interference from the Mather AFB
AN/MPN-I3 radar was not periodic as predicted, and actually
only appeared on the victim PPI display four times during a
20-minute period. Due to a tight time schedule during the
San Francisco area investigation, the emission spectrum and
antenna pattern of the Mather AFB AN/MPN-13 were not measured.
The measured propagation path loss from Mather AFB to Travis AFB
was found to be 173 dB (Table D-3). The predicted propagation
path loss was 179 dB. Measurements at Travis also showed that
there was a 4 MHz frequency separation in the operating fre-
quency of the two radars. Both the Travis AFB AN/FPN-55 radar
and the Mather AFB AN/MPN-13 radar are assigned to operate on
2800 MHz. Measurements of the Travis AFB radar receiver RF
frequency response were not made to determine if the maximum
signal response occurred at 2801 MHz. However, a 4 MHz fre-
quency separation could result in 17 dB of FDR (Figure C-10).
Another factor contributing to lighter interference than pre-
dicted was the antenna tilt angle of the victim radar.

Air Force radar personnel at Travis AFB said the tilt
angle of the AN/FPN-55 radar antenna was set at 4.25° rather
than the nominal 3.5° antenna tilt angle. The different
antenna tilt angle could also result in a 2 dB error in the
victim radar mainbeam gain (Figure A-2) used to calculate the
INR. It was also discovered that the AN/FPN-55 radar receiver
had an 8 dB noise figure. The initial INR calculation was
based on a 4 GB noise figure since the AN/FPN-55 radar re-
ceiver was reported to be identical to the ASR-5 radar.
Although measurements of the interferer emission spectrum and
antenna pattern were not made, the above factors could have
contributed in a 17 dB difference between the predicted and
actual INR resulting in lighter interference than predicted.
The predicted form of the Mather AFB AN/MPN-13 interference
on the Travis AFB AN/FPN-55 radar PPI display is shown in
Figure 5-11.


TER, 5 = P. Ss G5 i FDR; 5 = Ny (E-1)

It is shown in Appendix C that the FDR is emission spectrum
limited. The measured emission spectrum of the San Pedro
AN/FPS-90 is shown in Figure B-19, and indicates an FDR of
approximately 45 dB at the operating frequency (2801 MHz) of
the Los Alamitos AN/CPN-4 radar. The predicted FDR was 53 dB
(Figure C-12). Using a mainbeam gain of +24 dBi (corrected for
antenna tilt angle, 7 dB) and receiver noise level (Ny) of

-102 dBm, the calculated INR using equation E-l1 for coupling
from the San Pedro radar would be +65 dB. The calculated INR
of +65 dB indicates why a majority of the PPI scope was covered
by interference from the height finder when the AN/FPS-90 was
nodding in the direction of Los Alamitos. When the height
finder was not nodding in the direction of Los Alamitos, the
INR should be approximately 49 dB less (mainbeam-to-median
backlobe ratio of height finder antenna) which would give

an INR of 16 dB and still cause interference on the PPI display.

INR measurements made using the 8580 receiver and tapping
off the AN/CPN-4 IF preamplifier. output, yielded measured INR's
between 15 dB and 48 dB which is in close agreement to the pre-
viously discussed INR range.

Predicted interference to the Los Alamitos AN/CPN-4 from
the San Pedro AN/FPS-90 for antenna coupling of the victim
mainbeam with the backlobe of the height finder, using the PPI
simulation model, is shown in Figure E-l. The actual observed
interference agreed fairly well with the predicted interference
for antenna coupling of the victim mainbeam with the backlobe of
the height finder.

Long Beach ASR-5. Interference from the Long Beach ASR-5
was not observed on the Los Alamitos AN/CPN-4 PPI display. The
Long Beach ASR-5 emission spectrum was measured at Long Beach
to determine the FDR factor. The Long Beach ASR-5 emission
spectrum is shown in Figure B-13, and indicates an FDR factor
of 53 dB at the Los Alamitos AN/CPN-4 operating frequency of
2801 MHz. The predicted FDR was 47 dB (Figure C-9). The
predicted propagation loss was 19 dB less than the measured
propagation loss (149 dB, Table D-2). The median backlobe
level of the Long Beach ASR-5 was measured to be -11.8 dBi
(Table A-1). Also a comparison of Figures A-6 (line-of-sight
antenna pattern) and Figure A-24 (Long Beach ASR-5 environmental
antenna pattern measured at Los Alamitos) shows that the backlobe
level of the Long Beach ASR-5 antenna radiation is attenuated
by the foreground clutter at the Long Beach radar site. This
additional attenuation of the Long Beach ASR-5 backlobe level


LOS ALAMITOS AN/CPN-4 VICTIM RADAR MEASUREMENTS

The nominal characteristics of the Los Alamitos AN/CPN-4
radar are given in Table 4-2. Closed system measurements made
on the radar indicated that the nonsynchronous MDS INR was 6 GB
for the normal channel and 7 dB for the MTI channel with the
integrator off. A steady level of interference could be ob-
served at an INR of 10 dB for both the normal and MTI mode.

The receiver inherent noise level (N35) is -102 dBm.

The RSMS van dish antenna was approximately the same height
as the AN/CPN-4 antenna height. Therefore, the measurements
made at this site using the RSMS van dish should be fairly
representative of what the AN/CPN-4 antenna received. Possible
objects causing reflections at the site are discussed in
Appendix D.

The predicted interferers for the Los Alamitos AN/CPN-4
radar were:

Interferer Victim
Radar Freg. (MHz) Freq. (MHz) INR
San Pedro AN/FPS-90 2835 2801 25.5
Long Beach ASR-5 2777 2801 26.2

San Pedro AN/FPS-90. Interference from the San Pedro height
finder was observed on the PPI scope of the AN/CPN-4 at Los
Alamitos. The interference observed on the PPI scope varied
from interference occurring in a 5° sector when the height
finder was not nodding in the direction of Los Alamitos to
interference approximately covering 3/4 of the PPI display when
the AN/FPS-90 radar was nodding in the direction of Los Alamitos.
Because of the random scanning of the AN/FPS-90 mainbeam, it
was very difficult to determine the propagation loss from the
height finder. However, the RSMS van was used to measure the
peak power level received at Los Alamitos from the height
finder for a period of several hours. Figure D-6 shows a
sample of the measured data taken using the RSMS van dish
which has a 20 dB gain. Figure D-6 shows a maximum received
peak power level of +4 dBm. It is not positively known that
this +4 dBm level occurred when the height finder was nodding
in the direction of Los Alamitos. However, these types of
measurements were made over a 12-hour period, and +4 dBm was
the maximum peak received power. Correcting the +4 dBm level
for the gain of the van dish gives a peak power level at the
AN/CPN-4 antenna of -16 dBm (P;). The INR at the AN/CPN-4 IF
output caused by the San Pedro AN/FPS-90 can then be determined
by:

E-2


actually why the form of interference from the AN/CPN-4 was

not the same as predicted without making additional measure-
ments. Figure E-5 shows the form of the predicted interference
using the PPI simulation program. As seen in Figure E-5, the
predicted interference was extremely pessimistic when compared
to the observed interference. It was concluded that buildings
and trees along the propagation path caused the interfering
signal to be diffused causing a significant increase in propa-
gation loss.

MOUNTAIN VIEW ASR-5 VICTIM RADAR MEASURBMENTS

The ASR-5 radar site at Mountain View is an uncluttered
site located at the southern tip of the San Francisco Bay.
The Mountain View radar site was chosen as a detailed measure-
ment site with the major objective of obtaining propagation
path loss data on ducting phenomena which occurs in the bay area.
Propagation path loss data was obtained for predicted interfering
radars, and also radars which were not predicted as potential
interferers.

The ASR-5 radar at Mountain View has an antenna height of
26 feet. Both the RSMS van dish (height 14 feet) and omni
antenna (height 30 feet) were used to measure the power received
from the other radars in the bay area. Emission spectra of the
predicted interferers were also measured.

The nominal characteristics of the Mountain View ASR-5
radar are given in Table 5-2. The predicted interferers for
the Mountain View ASR-5 radar were:

Interference Victim

Radar Freq. (MHz) Freq. (MHz) INR (dB)
Almaden

AN/FPS-90 2778 2758 32
Almaden

AN/MPS-14 2793 2758 22
Mt. Tamalpais

AN/FPS-90 2737 2754 23


to Mountain View over the measurement period of one-half hour.
Due to the inability to coordinate several hours of propagation
measurements with ADC personnel, verification of the path as a
ducting path could not positively be made. The measured propa-
gation loss from Mt. Tamalpais varied from 155 dB to 169 dB
with an average rropagation path loss of 160 dB (Table D-3).
The predicted propagation path loss was 151 dB. Using the
measured emission spectrum to determine the FDR factor,

Figure B-18 shows the emission spectrum to be down 32 dB from
the fundamental frequency at 2754 MHz. The predicted FDR was
40 dB (Figure C-13). The backlobe antenna gain of the

Mt. Tamalpais AN/FPS-90 radar could not be measured. Using

a nominal antenna backlobe gain of -13 dBi for the Mt. Tamalpais
radar, the measured propagation loss and FDR, and the nominal
characteristics of the Mountain View ASR-5, the calculated

INR is 22 dB using Equation 3-1. The actual predicted INR

was 23 dB. Figure 5-6 shows the predicted form of the inter-
ference from the Mt. Tamalpais AN/FPS-90 radar to the Mountain
View ASR-5.

TRAVIS AFB AN/FPN-55 VICTIM RADAR MEASUREMENTS

The AN/FPN-55 radar site at Travis AFB is an uncluttered
site, and the RSMS van was able to locate approximately 30 feet
from the radar antenna. The AN/FPN-55 radar at Travis AFB has
an antenna height of 26 feet. Only the RSMS van dish (height
14 feet) was used to make measurements at the Travis AFB radar
site. The directional discrimination of the RSMS van dish
was required to suppress the AN/FPN-55 signal since the
operating frequency of the victim radar and potential inter-
fering radar were only separated by 4 MHz. In order to obtain
enough suppression of the Travis AFB AN/FPN-55 radar signal,
both RF and video blanking were required. The RF blanking
was achieved by using a pin diode modulator and the AN/FPN-55
radar STC pretrigged to turn off the modulator during the
transmission of the AN/FPN-55 pulse. The video blanking was
achieved using the AS-330 pulse train separator. The radar
characteristics of the AN/FPN-55 are given in Table 5-2. The
predicted interferers for the Travis AFB AN/FPN-55 radar were:

Interferer Victim
Radar Freq. (MHz) Freq. (MHz) INR (dB)
Mather AFB
AN/MPN-13 2797 2801 26

E-16