• 1274.58 . smaller signal at 1269.24
• 1332.66. smaller signal at 1327.54

• 1257.6 with weaker pulse at 1252.41
• 1349.6 with weaker pulse at 1344.41

Links:
Punta borinquen carsr radar specs.

New punta borinquen casr arsr-4 1274,1332 MHz radar specs: (top)

29apr13: measuring the radar blanking

    On 29apr13 i spoke with MS Sgt Bezos about the radar blanking in our direction. He had the radar blank 107 thru 111 degrees of azimuth (as it points at the AO). Spectra were taken before and after the blanking. Total power data was taken after the blanking was in place.

total power data:

    After the blanking was turned on data was taken with  the lbw receiver was centered at 1274.5 MHz. The setup was:

• lbw centered at 1274.5
• The signal was passed through a 5 MHz filter and then detected with a 2 usecond time constant.
• The detected signal was sampled at 1 MHz with the ri (12 bits).
• This was done for 48 seconds (4 radar rotations)

• The data was sampled at 1 usec but then smoothed,decimated to 40 usecond resolution.
• Each rotation is plotted in a different color (with offsets for display)
• The top frame is plotted vs time. The blanking occurs around 3.5 seconds.
•  The bottom plot is plotted vs azimuth (of the radar). They told me they blanked from 107 to 111 degrees of azimuth.
  
• For the azimuth, i used the first  signal dropout to be az=107 degrees. This is where they told me they started blanking.
• I don't see very strong backlobes of the radar.

• The 4 rotations have been over plotted (using different colors).
• top frame: plotted vs time
• the radar is blanked from 3.565 to 3.717 = .152 seconds
• bottom frame: plotted vs azimuth
• the radar is blanked from 107 to 111.62 degrees (assuming 107 is the first drop off).

Spectral data:

• The interim correlator used 9 level sampling, 1 second integrations.
• 12 1 second spectra show a complete radar rotation (with offsets for display)
• The white traces are with no blanking.
• The red traces are with blanking turned on.
• The traces with blanking on actually look to be the same strength as when blanking is turned off.
• The limited number of bits may have been clipping the signal at a level outside the blanking region
• A better test would have been to look outside the radar freqeuncy and see if the system was compressing less when the blanking was on.

Rfi hilltop monitoring:

    The rfi hilltop monitoring data at the radar frequencies was plotted for 29apr13 (.ps) (.pdf):

• The black trace shows the 1274.5 Mhz peak. The red trace is the 1332.5 Mhz peak
• The green line shows where the blanking was enabled.
• The max value prior to blanking was -14dbm.
• the max value after blanking was -25dbm
• So the blanking lower the signal by about 11db..
  

Summary:

• The punta borinquen radar began blanking the radar when it pointed at AO (on 29apr13).
• The radar blanked for azimuths 107 - 111 degrees of azimuth.
• Using the interim correlator, the radar spike remained about the same (before and after blanking).
• The hilltop monitoring saw the radar signal decrease by about 11db when blanking was enabled.
  
• We probably need to see if the radar is compressing the system with it's current blanking window.
  
• After the radar is accepted we may try to get them to increase the blanking window.
  

23apr13: First look at the radar.

    Data was taken on 23apr13 to characterize this new radar. The setup was:

•  za=2,az=286. Telescope was stationary during the datataking.
• lbw receiver, linear polarization, no filters.
  
• mock spectrometer
• file:000 - cfr=1300 MHz, 172 MHz bw, .1 second sampling of spectra. Take data for 60 seconds. starting around 11:45.
  
• file:100 - cfr=1271.5, 8.6 MHz bw, time domain, 8 bit sampling, 25 seconds of data.

• The dynamic spectra shows which birdies are coming from the same source.
• The radar rotate with a period of 12 seconds. When the radar points at ao, the birdie gets stronger
• Common radars:
• Punta salinas: 1232.65, 1241.60, 1247.77, 1256.59
• punta Borinquen: 1269.44, 1274.48, 1327.52, 1332.56
• FAA Radar: 1330,1350
• You can see that the 1274/1332 radar is not rotating the same as punta salinas or the FAA radar.

• Page 1: 60 second average of the 172 MHz bandwidth centered at 1300 MHz
• Top full band. the new radars are flagged in color
• the 1269 and 1327 birdies are much weaker than the other two.
• Middle,bottom:blowups  around the new radar frequencies.
• The bandwidth is about 1 MHz
• The signal probably saturated when it pointed directly at us.
• Page 2: Total power times series (.1 second resolution).
• top: 60 seconds of data. red is 1274.75, green is 1332.7 MHz. Blue vertical lines are placed every 12 seconds (the rotation period of the radar).
• Bottom: blowup when the radar pointed at AO.

• the signal was I/Q sampled at  8.6 Msamples/second centered at 1271.5 MHz. This contained th 1274.5 and the 1269 birdies.
  
• The total power was then computed for each sample (polA and B was then averaged).

Total power vs time folded at cumulative ipp of radar (.gif)

• The total power data stream was searched for the radar ipps
• There is a sequence of  5*ipp1 , 5*ipp2,5*ipp3. So the pattern repeats every 15 ipps.
• The image shows the total power data plotted  at this 15 ipp power.
• For the image the data was smoothed/decimated by 100 (to a resolution of 11 usecs).
  
• the 15 ipp period is 47.62088 milliseconds.
  
• You can see the 3 times when the radar pointed at the AO (the bright points).
• The narrow line to the right of the radar may not be real.
  
• The 8 bit samples saturated. squaring to get the power gave a constant output value for a few samples.
  

• Top: total power showing pulse duration. This .11 usec resolution.
  
• The first pulse lasts for 117 usecs
• there is a gap of about 150 useccs
• then a narrow pulse of 19 usecs.
• The power included the 1274.5 and the 1269.4 birdies.
  
• The blank space is probably when the  1332 and 1327 mhz pulses were active
• So then entire pulse period is about 300 usecs.
  
• Bottom: 25 seconds of data folded at the cumulative radar ipp: 47.62088 milliseconds
• The 3 different ipps are flagged in color

Summary:

• the punta borinquen carsr radar on 01apr13 around 14:00
• The radar frequencies are:
  
• freq: 1274.58,1332.66 with smaller birdies 1269.24,1327.54 MHz
• The large birdies are separated by 58 MHz
• The smaller birdies are 5.12 MHz below the larger birdies.
• Bandwidth : about 1 MHz
  
• ipps:
• 3 ipps: 2755.4, 3150.7, 3627.5 usecs
• Each ipp is repeated 5 times, then it steps to the next ipp
• The  15 ipp period is : 47.62088 milliseconds.
• Rotation period of  12 seconds.
• pulse length and order:
• 117 usecs 1274.5, 117 1332.5, 19 usecs 1327, 20 usecs 1269 MHz.
  
• The bandwidth at each freq is about 1 MHz.
  
• The radar will finish acceptance testing on 15may13.
  
• Problems:
• I think the 1332 MHz radar is interfering with the radar blanker.
• The radar blanker generates a total power time series with the 1330,1350 radar folded together.
• Unless there is a pretty narrow filter, the 1332 radar will end up in this time series.
• when the blanker searches for the FAA radar, it may get confused by this other set of pulses.
  

processing: x101/130423/lbwrdr_spc.pro  lbwrdr_tmd.pro

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