PULSE WIDTH ( VICTIM) =0-50vs

PRF € VICTIM) =1500.00rrs

PULSE WIDTHCINTERFERER )=0.70us » 2.00us
PREF CINTERFERER)=1095 .OOres » 278 -OOrrs
VIC. ANT. SWEEP RATE =20-00nen

INT. ANT. SWEEP RATE =15.00ren + 0-O0nen

WITH INITIAL REL. AZIMUTH =700e , 295080
INT. BEARING =110oe0 + 13500
MUTUAL ANT. GAIN THRESHGLD =-11.700er ,» 2.00o8

ie}

270

180

e090 e.-0. Ra ‘3b.00

= =
RANOE IN aut AKL nies

Figure 5-10. Simulated PPI Display of Alameda AN/MPN-1l With
Hayward AN/MPN-13 (Bearing 110°) and Almaden
AN/MPS-14 (Bearing 135°) Interference.


PULSE WIDTH ( VICTIM) =0-83us

PRF ( VICTIM) =810-.O0rrs
PULSE WIDTH( INTERFERER )=4 .00us
PRF CINTERFERER )=164 . O0res

VIC. ANT. SWEEP RATE =15-OOnen

INT. ANT. SWEEP RATE =5~.00Orn

WITH INITIAL REL. AZIMUTH =350oe0
INT. BEARING =200o80

MUTUAL ANT. GAIN THRESHGLD =-5.90oe:

i)

270

180

eco tk.00 ah. 8.00

0038.00 ab .00
RANGE IN NAUTICAL MILES

Figure 5-4. Simulated PPI Display of Sacramento ASR-4 With
Sacramento WSR-57 (4.0’usec mode) Interference.

5-14


Radar Interferers Victim INR

Freq. (MHz) Freg. (MHz) (dB)
Alameda
AN/MPN-11 2800 2793 20
Hayward
AN/MPN-13 2800 2793 25

During the measurements at Almaden, the AN/FPS-90 radar was
being actively used by the Air Force ADC, and could not be ex-
amined for verification of predicted interference. However,
heasurements were made on the AN/MPS-14 radar receiver.
Interference was observed on the AN/MPS-14 RHI scope from the
Alameda AN/MPN-1l radar. The interference appeared on the RHI
scope when the height finding radar nodded in a 45° sector in
the direction of the Alameda radar (bearing 321°). The Hayward
AN/MPN-13 radar was unoperational during the measurement period,
and therefore could not be confirmed as an interferer.

Figure 5-14 shows observed interference from the Alameda AN/MPN-11
radar.

Sacramento WSR-57 - Predicted interferers for the
Sacramento WSR-57 radar were:

Radar Interferers Victim INR
Freq. (MHz) Freq. (MHz) (dB)

Sacramento

ASR-4 2868 2887 14

Interference from the Sacramento ASR-4 radar was observed on
almost every scan of the victim radar when the WSR-57 was
operating in the 4.0 sec mode. The interference from the
ASR-4 radar appeared only at the bearing of the interfering
radar (37°), and covered approximately a 5° sector on the
victim PPI display. When the WSR-57 was operating in the

0.5 usec mode, no interference from the Sacramento ASR-4
radar was observed. The reason the interference of the

ASR-4 radar was not observed when the WSR-57 was operating

in the 0.5 usec mode was that the inherent noise level in

the victim radar receiver is increased by 8 dB due to a wider
IF bandwidth. Unpredicted interference at a bearing of 97°
was also observed from the Mather AFB AN/MPN-13 radar. The
predicted INR from the Mather radar was -l dB. The inter-
ference from the Mather AFB AN/MPN-13 radar was observed on
approximately one out of seven scans of the victim radar.

It is believed that the slow antenna rotation rate (4 rpm)
relative to the antenna rotation rate of the AN/MPN-13 (15 rpm)


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Travis AFB AN/FPN-55 radar from the Mather AFB AN/MPN-13 radar
is shown in Figure 5-1l. Because of the infrequency of the
observed interference, the interference was not able to be
photographed. Interference to the Travis AFB radar from the
Mather AFB radar is discussed in more detail in Appendix E.

Mather AFB AN/MPN-13 - Predicted interferers for the
Mather AFB AN/MPN-13 radar were:

Radar Interferers Victim INR

Freq. (MHz) Freq. (MHz) (dB)

Travis 2801 2797 23
AN/FPN-55

Beale 2800 2797 10
AN/MPN-15

Very light and intermittent interference was observed from
the Travis AFB AN/FPN-55 radar. The interference from the
Travis AFB AN/FPN-55 was only observed seven times over a
fifteen-minute period, and resulted in a 5° interference
wedge at a bearing of 220 to 260 degrees. The Travis AFB
AN/FPN-55 radar is at a bearing of 223°. One reason the
interference was lighter than predicted was that the antenna
tilt angle for the Mather AN/MPN-13 was set at 5.5° instead
of the nominal 3.5 degrees. The increased antenna tilt angle
could result in a decrease of the Mather AFB AN/MPN-13 radar
antenna mainbeam gain by 6 dB (Figure A-2). Also, both radars
were assigned to operate at 2800 MHz. However, measurements
made with the RSMS van showed a 4 MHz frequency separation
between the operating frequency of the two radars. It is not
known how much rejection of the interfering signal the 4 MHz
frequency separation would account for since the tuned frequency
of the victim radar receiver was not known. However, the
Frequency-Dependent-Rejection (FDR) curve in Appendix C
(Figure C-9) indicates that for a 4 MHz frequency separation,
the rejection would be 17 dB. The Beale APB AN/MPN-15 radar
was operating intermittently during these tests and was not
positively identified as an interferer. Figure 5-12 shows
the predicted interference from the Travis AFB AN/FPN-55
radar to the Mather AFB AN/MPN-13 radar, and Figure 5-13
shows a photograph of the actual observed interference.

Almaden AN/MPS-14 - Predicted interferers for the
Almaden AN/MPS-14 radar were:

5-21


PULSE WIDTH ( VICTIM) =4-.00ue

PRF ( VICTIM) =164.00res
PULSE WIOTH( INTERFERER )=0 .83us
PRF CINTERFERER )=610 -O0res

VIC. ANT. SWEEP RATE =4.00nen

INT. ANT. SWEEP RATE =15 .OOnen

WITH INITIAL REL. AZIMUTH =20Doe0
INT. BEARING =37oee

MUTUAL ANT. GAIN THRESH@LD =-3.00ce:

i)

189

To. a PONT on)

Cary 79.70 Bou"
RANGE IN NAUTICAL ILE!

Figure 5-15. Simulated PPI Display of Sacramento WSR-57 with
Sacramento ASR-5 Interference.

5=27


270

Figure 5-12.

PULSE WIDTH ( VICTIM) =0.70us

PRF ( VICTIM) =1095 .00res
PULSE WIDTH( INTERFERER )=0 .83us
PRF CINTERFERER )=900 -O0res

VIC. ANT. SWEEP RATE =15-00nen

INT. ANT. SWEEP RATE =13.-50ren

WITH INITIAL REL. AZIMUTH =350o80
INT. BEARING =22380

MUTUAL ANT. GAIN THRESHOLD =1 .OOcer

i)

180

600 foe hone
RANGE IN NAUTICAL MILES

Simulated PPI Display of Mather AFB AN/MPN-13
with Travis AFB AN/FPN-55 Interference.

5-23


PULSE WIDTH ( VICTIM) =0-83us

PRF ( VICTIM) =1002.O0res
PULSE WIDTH( INTERFERER )=2 -00us
PRF CINTERFERER J=356 . 00 res

VIC. ANT. SWEEP RATE =15.00nen

INT. ANT. SWEEP RATE =0.0Onen

WITH INITIAL REL~ AZIMUTH =295ce0
INT. BEARING =291o80

MUTUAL ANT. GAIN THRESH@LD =-12.90ce0

0

270

180

x 0s shoe a
feo Ringe a Maurice nes

Figure 5-8, Simulated PPI Display of Oakland ASR-7 With Mt.
Tamalpais AN/FPS-90 Interference.

-18

u


van instrumentation was used to determine why predicted inter-
ference did not appear on the victim PPI display or why un-
predicted interference appeared on the PPI display. The
detailed measurements made during the second phase of the
measurement program are discussed in Appendices A through E.
Appendix E gives a detailed discussion of the predicted and
observed interference at two radar sites using the measured
data discussed in Appendices A through D to explain the
differences between predicted and observed interference.
Appendix F gives a general outline of the measurement plan,
and Appendix G discusses the RSMS instrumentation used in the
San Francisco area radar measurements.

Sused Preliminary Radar Site Measurements

The purpose of these measurements was to verify predicted
interference situations to the extent that the live environ-
ment conditions and parameters used to predict the interference
existed. This set of measurements was not comprehensive with
the main objective to compare predicted interference with the
live environment conditions for 8 victim radar sites. These
measurements were made during normal operation of air traffic
control.

During the preliminary radar site measurements, the victim
radar's controls were set as follows:

cr

ON anc OFF
Polarization: Linear and Circular

FAK radars in the Sa:. Francisco area operate in the MTI
mode for full PPI scope range and with integrators on all the
time. The stagger was turned off on the victim radar so that
the AS-330 pulse train separator could be used to identify the
interfering radars by PRF. The following is a discussion
of the predicted and observed interference. The vredicted
interferers for each victim are listed in Table 5-4 with
INR's > 10 4B.

Sacramento ASR-4 ~- Predicted interferers for the Sacramento
ASR-4 radar were:

Radar Interferer Victim
Freq. (HEz) Freq. (Miz)
Sacramento 2837 2368 ~
WSR-57

* Por .5 usec mode of WSR-57
** For 4.0 psec mode of WSR-57

5-20


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of radars 10, 16 and 21 which employ fixed magnetron output
tubes. Table 5-3 shows the operational frequency range, and
the assigned frequency of the radars in the San Francisco
environment. Additional information on the magnetron tube
employed in each radar, and the magnetron tuning range is
discussed in Appendix B.

5.3 COMPARISON OF PREDICTED AND OBSERVED INTERFERENCE

The following is a comparison of the interference that
was observed during the 2.7-2.9 GHz spectrum resource assess~
ment measurement program in the San Francisco area and pre-
dicted interference. The San Francisco area measurement plan
consisted of a two-phase investigation similar to the investi-
gation conducted in the Los Angeles area.

The first phase involved preliminary radar measurements
which consisted of on-site verification of predicted interference.
Potential interference situations in the San Francisco area
were determined by calculating the INR at the victim radar
receiver IF output using Equation 3-1 with the following
empirical correction factors:

l. Gp, = -13 dBi, based on measurements made in the
2 Los Angeles investigation.
2. Lp,. = RAPIT point-to-point model plus correction
+3 fecter for building and structure attenua-
tion (discussed in Appendix D).
3. Ty = Insertion loss of both victim and interfering

radar. A 2 dB insertion loss was used at
both ends (Reference 31).

The above modifications to the INR calculation procedure are
discusse@ in detail in Appendices A and D. Table 5-4 shows the
predicted radar coupling situations in the San Francisco environ-
ment where the calculated INR was greater than 0 dB. For dual
channel radars (FAA ASR radars), only worst case (minimum fre-
quency separation for dual channel radars) INR's are shown in
this Table. As in the Los Angeles investigation, the actual
predicted interference situations are those cases listed in
Table 5-4 when the INR > 10 dB. Also, as in the Los Angeles
investigation, the PPI Simulation Program was run to determine
the form of the interference on the victim PPI display.

The second phase of the San Francisco area investigation
was similar to the Los Angeles area investigation. The RSMS


Alameda AN/MPN-11 - Predicted interferers for the Alameda
AN/MPN-11 were:

Radar Interferers Victim INR

ee Freq. (MHz) Freg. (MEz) (dB)
Hayward 2890 2800 33
AN/MPN-13

Almaden 2793 2800 21
AN/MPS-14

Interference from the Hayward AN/MPN-13 was observed on the
Alameda AN/MPN-11 PPI display on approximately every scan of
the victim radar. The interference from the Hayward radar was
coupled in through the victim antenna mainbeam and backlobe,
and resulted in interference wedges of 3° to 15°. Interference
from the Almaden AN/MPS-14 radar could not be verified since
the radar was not operating during the month of November.
Interference from the Almaden and Mt. Tamalpais AN/FPS-90
radars was also observed, but only when the height finding
radars were nodded directly at the Alameda AN/MPN-11 radar.
Interference from these height finding radars was predicted,
but is not listed in Table 5-4 since the Table is only for
mainbeam of the victim radar coupling with the sidelobe of
the interfering radar. Figure 5-10 shows the predicted form
of the interference from the Hayward AN/MPN-1l radar and
Almaden AN/MPS-14 radar on the Alameda NAS AN/MPN-11 PPI
display. Photographs of the interference were not taken.

Travis AFB AN/FPN-55 - Predicted interferers for the

Travis AFB AN/FPN-55 radar were:

Radar Interferers Victim INR

Freq. (MHz) Freq. (MHz) (dB)
Mather 2797 2801 26
AN/MPN-13

Interference from the Mather AN/MPN-13 was only observed a

few times during the video tape recordings, and was not
periodic as predicted. The interference from the Mather
AN/MPN-13 radar was observed at bearings of 290°-315° and
around 20°. The Mather AN/MPN-13 radar is at a bearing of 42°.
The occurrence of the interference on the victim PPI display
at bearings other than the bearing of the Mather AFB radar

was most likely due to coupling of the Mather AFB AN/MPN-13
radar antenna mainbeam with a high backlobe of the Travis AFB
AN/FPN-55 radar antenna. Predicted interference to the

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5-25



SECTION 5

SAN FRANCISCO AREA INVESTIGATION

5.1 INTRODUCTION

This section discusses the investigation and measurement
program conducted by OT in the San Francisco area to assess the
capability and techniques used to predict radar-to-radar inter-
ference, and to make refinements to the prediction model. The
investigation was made during the period of August to December
1975 with measurements being conducted from November 3 to
November 17, 1975. The environment included all radar deploy-
ments in the 2.7 to 2.9 GHz band within 200 statute miles of
San Francisco. Included in this section is a comparison
between predicted and actual observed interference at eight
radar sites visited in the San Francisco area, and environmental
observations. A detailed comparison of the measured data taken
during the investigation with the various component models used
to predict radar-to-radar interference is given in Appendices A
through E.

5.2 ENVIRONMENT OF 2.7-2.9 GHz BAND

The environment for the San Francisco area was determined
from two sources: 1) Western Region FAA Frecuency Manager
(Reference 51), and 2) Government Master File (GMF). Com-
parison was made of the environmental lists received from the
two sources, and differences resolved by contact with the
area frequency coordinator. It was determined that there are
a total of 21 radars within a 200 mile radius of San Francisco
operating in the 2.7 to 2.9 GHz band. Table 5-1 lists the
location, nomenclature and function of these radars. Figure 5-1
shows the location of these radars on a San Francisco area map.
The equipment characteristics of the radars are given in Table 5-2.

During this San Francisco area investigation, the RSMS van
was used to verify the frequency assignments obtained from the
area coordinators. All the radars in the area were found to be
operating within a few megahertz of their assigned frequency.
However, the operation of a radar not listed in the GMF or the
FAA area coordinator list was discovered. An actual site visit
verified the operation of an AN/FPS-90 at Mt. Tamalpais by the
Air Force.

All the radars in the San Francisco environment employ a
tunable conventional magnetron output tube with the exception

5=L


PULSE WIOTH ( VICTIM) =0.83us

PRF C VICTIM) =810-.00rre
PULSE WIOTH( INTERFERER )=0 .S0us
PRF CINTERFERER )=545 .00res

VIC. ANT. SWEEP RATE =15.00nn

INT. ANT. SWEEP RATE =5 .0Onen

WITH INITIAL REL. AZIMUTH =350oe0
INT. BEARING =200oe0

MUTUAL ANT. GAIN THRESH@LD =-14.9008

0

270

180

Figure 5-2, Simulated PPI display of Sacramento ASR-4 With
Sacramento WSR-57 (0.5 usec mode) Interference.

5-12


With the WSR-57 antenna set at normal operating elevation (1
degree), interference from the Sacramento WSR-57 was observed
on the Sacramento ASR-4 PPI display for both the 4.0 and 0.5 usec
pulse width operating modes of the WSR-57. The WSR-57 radar
was located at a bearing of 200°. Interference from the WSR-57
radar was heavier for antenna coupling of the interferer main-
beam to the victim backlobe, than for antenna coupling of the
victim mainbeam to the backlobe of the interferer. This was
due to the higher antenna mainbeam gain of the WSR-57 radar
than the ASR-4 radar; taking into consideration the antenna
tilt angles, the mainbeam gains are 33 dBi and 27 dBi, respec-
tively. Also, the much slower rotation rate of the WSR-57
antenna caused the interference to be heavier for antenna
coupling of the mainbeam of the interfering radar with the
backlobe of the victim radar. Because of the higher emission
spectrum skirt levels of the WSR-57 radar when operating in the
0.5 usec mode, the interference was greater when the WSR-57

was operating in the 0.5 usec pulse width mode than in the

4.0 usec pulse width mode. The 0.5 usec pulse width mode of
the WSR-57 radar caused interference wedges of 10° to 90°, and
the 4.0 usec pulse width mode caused interference wedges of

10° to 40°. The predicted and observed interference for 0.5 usec
pulse width mode of the WSR-57 radar is shown in Figure 5-2

and Figure 5-3, respectively. Figure 5-4 and Figure 5-5 show
the predicted and observed interference for the 4.0 usec pulse
width mode of the WSR-57 radar.

Mountain View ASR-5 - Predicted interferers for the
Mountain View ASR-5 radar were:

Radar Interferer Victim INR

Freq. (MHz) Freq. (MHz) (aB)

Almaden 2778 2758 32
AN/FPS-90

Almaden 2793 2758 22
AN/MPS-14

Mt. Tamalpais 2737 2754 23

Interference was observed from the Almaden and Mt. Tamalpais
AN/FPS-90 radars on both channels of the Mountain View radar.
Because of the-alternating monthly operating procedure of the
Almaden AN/MPS-14 and AN/FPS-90, potential interference from
the AN/MPS-14 could not be verified. Interference from the
Almaden AN/FPS-90 appeared on approximately every sweep of
the victim radar at the interferer bearing of 144°. The
interference from the Almaden radar usually appeared as a 3° to
40° wedge of interference. Interference from the Mt. Tamalpais

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PULSE WIDTH ( VICTIM) =0.83us

PRF ( VICTIM) =900.O00rrs
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VIC. ANT. SWEEP RATE =13.00ren

INT. ANT. SWEEP RATE =15.00nen

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MUTUAL ANT. GAIN THRESH@LD =-1.70o8

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Mather AFB AN/MPN-13 Interference.


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5-4


AN/FPS-90 radar only appeared on the Mountain View ASR-5 PPI
scope about one out of four scans of the victim radar. The
interference from the Mt. Tamalpais AN/FPS-90 radar also
appeared in wedges of 3° to 30° at a bearing of 300° to 360°
on the victim PPI scope. The predicted and observed inter-
ference from the Almaden and Mt. Tamalpais AN/FPS-90 radars
to the Mountain View ASR-5 radar is shown in Figure 5-6 and
Figure 5-7, respectively. A more detailed discussion on
interference to the Mountain View ASR-5 radar is discussed
in Appendix E.

Oakland ASR-7 - Predicted interferers for the Oakland
ASR-7 radar were:
Radar Interferers Victim INR
Freq. (MHz) Freq. (MHz) (dB)
Mt. Tamalpais 2737 2733 38
AN/FPS-90

Heavy interference from the Mt. Tamalpais AN/FPS-90 radar
was observed on the Oakland ASR-7 PPI display when the enhancer
was off. With the enhancer off, the interference covered 36°
of the victim PPI display. The interfering source was positively
identified by having the Mt. Tamalpais AN/FPS~90 radar trans-
mitter turned on and off.

The interference from the Mt. Tamalpais radar was heavier
than predicted due to the fact that both the interferer and
victim radars were not operating on their assigned frequency.
The "B" channel of the Oakland ASR-7 radar is assigned to
2728 MHz, but was operating on 2733 MHz. Also, the Mt. Tamalpais
AN/FPS-90 radar is assigned to 2740 MHz, but was operating at
2737 MHz. Therefore, there was only a frequency separation of
4 MHz between the interferer and victim radar. Using the
Frequency-Dependent-Rejection (FDR) curve given in Appendix C
(Figure C-13), the decreased frequency separation would result
in a 10 GB increase in the INR.

When the victim radar enhancer was turned on, the inter-
ference from the Mt. Tamalpais radar was significantly reduced,
and only appeared randomly on the victim PPI display at the
bearing (291°) of the interfering radar as 5° to 20° inter-
ference wedges. When the enhancer and log FTC modes of the
victim radar were used, the interference from the Mt. Tamalpais
radar was eliminated. However, the FAA normally operates the
Cakland ASR-7 radar in the enhanced MTI mode, and does not use
the log FTC mode. The predicted and observed interference from
the Mt. Tamalpais radar is shown in Figure 5-8 and Figure 5-9,
respectively.


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5-3


caused occasional coupling of the victim antenna mainbeam
with the interferer antenna mainbeam or major sidelobe. The
interference from the Mather AFB AN/MPN-13 radar covered
approximately a 10° sector at the bearing of the Mather AFB
radar (110°). Interference was also observed from the

Mt. Tamalpais AN/FPS-90 radar at a bearing of 217° when it

was coordinated to have the Mt. Tamalpais radar nodding in

the direction of the WSR-57 radar. The interference from

the Mt. Tamalpais radar caused an interference wedge of 3°

on the victim PPI scope. The form of the predicted inter-
ference to the Sacramento WSR-57 radar when operating in the

4 usec pulse width mode from the Sacramento ASR-4 radar is
shown in Figure 5-15. Figure 5-16 shows observed interference
to the Sacramento WSR-57 radar from the Sacramento ASR-4 radar,
Mather AFB AN/MPN-13 radar and Mt. Tamalpais AN/FPS-90 radar.

5.362 Summary of Observed and Predicted Interference

For the eight radar sites visited during the preliminary
radar site measurements, there were 13 predicted interference
cases of mainbeam-to-backlobe antenna coupling. However, due
to some of the radars being inoperative during the preliminary
radar site measurement program, only 10 predicted interference
cases could be verified. All 10 of the predicted interference
cases that could be verified were observed during the prelimi-
nary site visits. In general, the predicted form of the inter-
ference on the PPI display was close to the actual observed
interference with the exception of three cases: 1) Mt. Tamalpais
AN/FPS-90 interference to the Oakland ASR-7 radar, 2) Mather AFB
AN/MPN-13 interference to Travis AFB AN/FPN-55 radar, and 3)
Travis AFB AN/FPN-55 interference to Mather AFB AN/MPN-13
radar. There was also one case of unpredicted interference
that was observed (Mather AFB AN/MPN-13 radar interference to
the Sacramento WSR-57 radar). However, it appeared that the
interference from the Mather radar was due to coupling of the
victim antenna mainbeam to the interferer antenna mainbeam or
major sidelobe, and not victim antenna mainbeam coupling with
the interferer antenna backlobes which was the coupling mechanism
used to predict interference.

The San Francisco area investigation showed a significant
improvement over the Los Angeles area investigation in the
correlation between predicted and actual observed interference.
It is believed that this improvement in interference prediction
capability was a result of:

1) incorporating empirical propagation loss factors for
buildings and man-made obstacles into the overall
propagation path loss (see Appendix D).


RADAR

AUBWNH

worn

10

11
12
13
14
15

16
17
18
19
20

21

LOCATION OF 2.7-2.9 GHz RADARS

TABLE 5-1

IN SAN FRANCISCO AREA

CITY/BASE
Present FAA

Monterey

Fresno
Sacramento *
Mountain View **
Marysville
Oakland

Present
Lemoore
Vallejo
Alameda
Present
Monterey

Present

Travis AFB
Castle AFB
Mather AFB
Beale AFB
Hayward ANG

Present
Cambria
Almaden
Almaden

Point Arena
Mt. Tamalpais

Present

Sacramento

NOMENCLATURE

LATITUDE

LONGITUDE

Airport Surveillance Radars

ASR-3 36
ASR-4 36
ASR-4 38
ASR-5 37
ASR-5 39
ASR-7 afi

Navy Ground

35 16 121 50
46 51 119 43
39 56 121 24
25 38 122 00
07 49 L216:27,
42 23 E22513

Control Approach

ASR-5 36 20 44 119 54

MPN-5 38 05 06 122 16

MPN-11 37 47 23 122::19
Navy Tracking Radars

APS-20 36 35 52 L2052:
AF GCA Radars

FPN-55 38 16 08 121 54

FPN-47 37 22 34 120 33

MPN-13 38 33 51 d2beas,

MPN-15 39 08 12 121 26

MPN-13 37 40 00 122 07

AF Height Finding Radars

FPS-G 35
MPS-14 37
FPS-90 37
FPS-90 38
FPS-90 37

NOAA Weather Radars

WSR-57 38

* Joint FAA-AF use
** Joint FAA-N use

Sleds 121 53
09 38 L253
09 38 £24°53
RE) 123 32
55 45 122 35
35 00 121 29

09
06
14
50
35
27

Radars

18
52
20

25

58
03
19
00
00

46
47
47
55
20

00


2) changing the median antenna backlobe level from
-10 dBi to -13 dBi.

3) including transmission line insertion loss of the
victim and interferer radars.

5.4 ENVIRONMENTAL OBSERVATIONS

Interference was observed at all eight of the radar sites
visited in the San Francisco area investigation. Three of the
FAA radars (Sacramento ASR~4, Mountain View ASR-5, and Oak-
land ASR-7) and one GCA radar (Alameda AN/MPN-11) were con-
sidered to have a moderate amount of interference on their
PPI display. A look at Table 5-3 shows that all the radars
in the San Francisco Bay are assigned to operate in the 2.7
to 2.8 GHz band, and all the radars in the Sacramento area
are assigned to operate in the 2.8 to 2.9 GHz band. It is
believed, that if the whole 200 MHz band was utilized in the
San Francisco Bay area and the Sacramento area, interference
between the radars in these areas would be significantly
reduced. The present radar frequency assignment distribution
in the San Francisco and Sacramento areas is due to past
history frequency assignments, and removal of radars from
the environment.

Information on planned deployment changes in the 2.7 to
2.9 GHz band in the San Francisco area was obtained from the
various government agencies (References 48 through 50), and
is given in Table 5-5. The only known planned dual frequency
radar for the area is the Alameda NAS ASR-8 scheduled to
replace the AN/MPN-1l radar. Due to known ducting problems
in the bay area (see Appendix D), consideration of the ducting
phenomena must be given in determining frequency assignments
for the new Alameda ASR-8 radar. A height finding radar
(AN/FPS-6,90) is scheduled for Half Moon Bay as part of the
joint FAA/DOD surveillance system. The height finding radars
at Cambria, Almaden and Mt. Tamalpais will eventually be
phased out once the joint FAA/DOD surveillance system becomes
operational. The Monterey AN/APS-20 radar has been removed
from the band. The Beale AFB AN/MPN-15 radar will be removed
in FY 78 after an ILS is installed. A detailed investigation
on the accommodation of planned future radar deployments in
the 2.7 to 2.9 GHz band in the San Francisco area will be
given in a subsequent OT report.

5-29


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PULSE WIDTH ( VICTIM) =0.83us

PRF ( VICTIM) =1125.00res

PULSE WIOTH( INTERFERER ) =2 -00us » 2.00%
PRE cCINTERFERER)=556.00res » 278-O00rrs
VIC. ANT. SWEEP RATE =15.00nen

INT. ANT. SWEEP RATE =0-00nes » O-O0nen

WITH INITIAL REL~ AZIMUTH =295ne0 » 295o00
INT. BEARING =301 cee + 1440¢0
MUTURL ANT. GAIN THRESHGLD =2.-1008 --B «9008:

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Figure 5-6.

180

00 e039

fave uf Reurrcae nites
Simulated PPI Display of Mountain View ASR-5 With
Alameda AN/FPS-90 (Bearing 144°) and Mt, Tamalpais
AN/FPS-90 (Bearing 301°) Interference.