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    sband radar experiments has seen intermittent rfi around 2380 MHz. I've also seen this when doing the x102 runs with sband. On 09aug15 2 azimuth swings were done to look at the rfi. the setup was:

• sbn receiver (about 120 MHz centered at 2380 MHz)
• az 270 to 630 and back at .35 degs/sec. dome at 18 degs za
• 750 IF with 60 MHz narrow band filter installed.
  
• Mock spectrometer:
• 80 MHz bw, 8192 channels. 10ms sampling (then averaged to 1 sec).

Processing the data:

• dynamic spectra were made for each azimuth swing.
• For each azswing:
• compute median bandpass and use this to bandpass correct each spectra
• Use rfi free channels around 2370 to flatten the spectra in time (to remove continuum sources)
• Clockwise dynamic spectra (.gif)
• rfi:
• 2345-2350 : WCS band D (ATT owner)
• 2357.5 - 2366 : unkown.. no known licensee
• 2372.5 - 2391: unknown. probably a harmonic or intermod
• 2397.5 - 2406: Should be above 2400. Jumped back to 2400 on 10aug15. Previous abusers..
  
• Counter clockwise dynamic spectra (.gif)

I also made total power plots vs azimuth averaging over the main rfi blocks (.ps) (.pdf)

• Page 1: total power vs az position
  
• Each frame is a separate rfi block
• Black is the Clockwise swing, red is the CCW swing
• The dashed green lines are at multiples of 90 degrees.
• Top: 2357.5 to 2367.5 rfi.
• The peaks repeat so it is at a fixed location and probably  steady.
• The peak is at an az of 130 deg
• Middle: 2397.5 to 2412.5
• Peak at az=322. and lots of reflections at 180 deg.
• Could 322 be the control room/building 1,2?
  
• This used to come from yiyi avilars tower.. where we saw a 186 degree peak.
• This moved up to 2400 MHz on 10aug15.
• Bottom:2373-2390.8
• this also repeats in azimuth so it is not intermittent in time.
• the peak is at az=276.7. This has the azimuth arm perpendicular to yiyi's tower (at 186).
• This does not correlate with the other 2
  
• Page 2: first 30 spectra of the cw az swing.
• offsets were added for plotting
• these bands look like ofdm (when blown up you can see the individual channels.
• 2373-2390 rfi:
• You can see where this rfi gets strong then weak as the az passed through 276 degrees
• It has a bandwidth of about 20 MHz
• there is a large spike at the center of the band... 2382 MHz. 
• Most of these bands are 5 or 10 MHz.This might be a harmonic of a higher band
• We should change the cfr by a few MHz and see if this move by twice the value.
• a 10 MHz rfi at 2436MHz with peaks at 270,90 was seen in azimuth swings back in 12oct11

Summary:

rfi block	az Peaks	source
2357.5 - 2367.6	130.. but lots of other peaks	unknown. haven't found a legal license for this freq in pr..
2373 - 2390.8	az peak 276.7	probably yiyi's tower 20 MHz Wide center tone:2382 very strong most likely a harmonic or intermod
2397.5-2412.5	peak 322, lots of power at 185	moved up to 2400 on 10aug15 this was coming from yiyi's tower back in 2011

 

todo:

• got to az=276.7, za=18 with sbw and see if the 2373 rfi is there. It uses a different mixing scheme so if it is internal to our system it might come at at a different spot
• with sbn, take data with current config, then move cfr by 2 MHz. If it is a harmonic it will probably move by N*2MHz.
• If it is external, use spectrum analyzer with narrow bandwidth to look at tone at 2382. Get a direction from the platform.
  

processing: x101/150809/azswing_plot.pro