09aug15: azimuth swings showing direction for peak
05sep15:look to see if rfi created in our if/lo.

Intro

  sband radar has been noticing occasional rfi centered on 2380 MHz.

• Looking at the x111 data, you can see rfi at 2380 MHz starting around aug2014.
  
• Azimuth swings done 21aug15 showed that this rfi was coming from a particular azimuth direction (maximum when az equaled 276 degs). This is most likely the azimuth arm perpendicular to yiyi avila's tower. The swings showed that the variability was from the direction, not the time variation of the signal.

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05sep15: See if rfi created in our if/lo.

    There is very strong rfi above 2400 MHz (the ism band). If the 2380 MHz rfi was created in our if/lo (as an intermod or a harmonic), you would expect the location of the rfi to be a function of where the "creating rfi" was located in the if/lo band. If you changed the center of the if/lo band, the location of the intermod/harmonic should move in frequency,

    On 05sep15 i looked to see if the 2380 MHz rfi moved in frequency as i shifted the center of the if/lo band.
The plots show the location of the 2380 MHz rfi as i changed the if/lo settings (.ps)  (.pdf):

• The mock spectrometer was used to record the data. It uses a 2nd IF of 325 MHz.
• The table shows how the data was taken

• page,frame	rcvr	1st Mixer	Sky Cfr	A/D Cfr
  P1, top	sbn	750MHz	2380	2380
  P1,middle	sbn	750 MHz	2370	2370
  P1,bottom	sbn	10GHz upconverter	2380	2380
  P2,top	sbn	10GHz upconverter	2385	2380
  P2,middle	sbn	10GHz upconverter	2385	2385
  P2,bottom	sbw	10GHz upconverter	2360	2360

  
  

Summary:

• Moving the center of the IF1 band or IF2Band did not move the final frequency of the 2382 MHz rfi.
• the 750MHz mixer and the 10GHz upconverter both gave the same results.
• sbw gave the same frequency as sbn.
• Looks like the rfi must be before the 1st mixer.. either in the dewar, or actually being broadcast over the air.

processing:x101/150905/sbnrfi.pro