Some "other" radar Info

feb 2001

1. 1270/1290 Mhz radar. (12feb02)
2. (1366.2,1382.66)  (1324,1340), (1387.3/1371.0) lband radar 12feb01
3. 425 Mhz radar 06aug01.
4. 1371,1387.2 Mhz (27feb03)
5. 2900-3100 Mhz pico deleste. sps-48
6. asr 4/9/11 FAA surveillance radar specs (purloined document..)
7. link to FAS aerostat info

1. 1270/1290 Mhz radar. (12feb02) (top)

    This radar is a fps20-93a and is part of the 140acs located at the end of the runway at remy in one of the domes. It has a local operator but is controlled by the people at punta salinas. Its main coverage is to the west of the island
    I took 40 seconds of data on 12feb02 when the radar was at 1270 Mhz. I complex sampled a 1 Mhz bandwidth centered at 1270 Mhz using lband wide. The measured parameters were:
  • rotation rate 12 seconds.
  • pulse width about 5 useconds (a single pulse). The spectra of 10 secs of data is about 200 Khz bw. The plot is centered at 1270 Mhz but i'm not sure about the frequency direction (i didn't check the i/q inputs for the complex sampling).
  • ipp : there are 3 ipps that follow in sequence: 2782,2782, then 2741 useconds. The long term average of the 3 ipps is 2768.31 usecs. The image of the total power  ipp phase vs time used the average ipp to fold each horizontal line of the image. This caused 3 stripes to appear on the image. The two ipps of 2782 march to the right since they are longer than the average, then the 3rd ipp of 2741 causes it to jump back to the left. It looks like the 3 echos are in the same ipp (horizontal line) but they are each offset by 1 ipp. The pulse phase drifts by 600 useconds in 10 seconds (6 parts in 10-5) which is not very stable. You can also see the beam pointing at us every 12 seconds (at 20 and 32 seconds).
  • This radar is a fps20-93a and is part of the 140
  • beamWidth .05 secs or 1.4 degrees.
  • When the 1270,1290 are both running, they are transmitted simultaneously (verified mar11 using square law detector).  Talking to the punta salinas folks, one freq is horizontal while the other is vertical polarization. This causes intermods in the receivers spaces 20 Mhz about the rf frequencies
  •     The rfi hilltop monitoring for the year 2001 shows how often the 1270 and 1290 freq was used. The black plot is the 1270 Mhz. The red plot is 1290 Mhz. The green crosses shows when the 430 Mhz transmitter was on (this causes a birdie at 430*3=1290 Mhz and should not be confused with the 1290 Mhz radar). From the plots you can see that they switched from 1290 to 1270 around daynum 190 of 2001 (probably at our request).

    2. (1366.2,1382.66)  (1324,1340), (1387.3/1371.0)  12feb01. (top)

              2 frequencies    1366.2 /1382.66 Mhz run together
              2 frequencies     1324/1340          Mhz run together (these 2 are approximate frequencies)
    rotation rate                   2 seconds  (1.94secs)

    10ms 1366.2  then 10ms 1382.66, 10ms 1366.2 etc..
    10ms 1324 then 10ms 1340 ..etc
    within each 10ms cycle:
    pulse spacing : about 252 usecs for 1 cycle and 394 for another.  not sure when then switch
                               (these pulse width measurements are not very accurate or there may be some
                                 variation going on because i saw other spacings).
    pulse width: varies from 8usec down to maybe 1 or 2 usecs.
    Direction: east of the observatory.
    strength   : >= faa radars at 1330,1350
    radartype: may be an mk23 naval target acquisition radar for the NATO sea sparrow missile system.

        The 1366/1382  and 1387.3/1371.0 were refered to as a "landing systems" used in the naval exercises  (by the frequency coordinator at rosy roads). The 1387.3/1371.0 was not observered on 12feb01 but was seen 06nov01 with a 2. second period. The modulation was not measured on 06nov01 but it is probably the same as the 1366/1382.

    3. 1371,1387.2 Mhz (27feb03). (top)

    This looks like the radars described in 3. above. I used the spectrum analyzer, squarelaw detectors and scope to get the parameters.
    The radar switches between the two frequencies about every 6 millisecs (24 ipps freq1 then 24 ipps freq2, 24 ipps freq1 etc).

    pulse width: typically 5usec but gets as narrow as 1 usec
    ipp: averaging 24 ipps gave : 250 usecs. i didn't check for variation within the ipps
    beamwidth: it took 40millisecs to go min to min as the beam swept  around.
    rotation rate: (1.95 secs).

    4. 425 Mhz radar 06aug01. (top)

    10-13 usec pulse duration with  chirped frequency. bw about 6 Mhz.
    rotation period 10 seconds. Looks like it's saturating the system (doesn't get stronger as it rotates ). We saw the rotation strength change when we used the whip antenna. This may be the "typical" radar drug plane that happened to be flying close to the observatory. There were war games in vieques so it may have been a plane flying above AO in support of this.

    5. 2900-3100 pico del este radar. (top)

    SPS-48 radar on pico del este. radiates at 9 distinct freq. simultaneously. peak power output (eirp): prf: 640 hz with some jitter
    rotation rate: 15 rpm (4 secs) , pulse width 26.5 usecs.
    Most emission in the 2990 to 3060 range. It appears that eh 9 freq can be chosen by the operator anywhere within the band to adjust to range requirements.