sbn azswings 09aug15
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
- 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
- 2345-2350 : WCS band D (ATT owner)
- 2357.5 - 2366 : unkown.. no known licensee
- 2372.5 - 2391: unknown. probably a harmonic or
- 2397.5 - 2406: Should be above 2400. Jumped back to
2400 on 10aug15. Previous
- Counter clockwise
dynamic spectra (.gif)
I also made total power plots
vs azimuth averaging over the main rfi blocks (.ps)
- 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
- 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.
- this also repeats in azimuth so it is not intermittent
- 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...
- 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
|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
|peak 322, lots of power at 185
|moved up to 2400 on 10aug15
this was coming from yiyi's tower back in 2011
- 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