• cband high receiver
• 11mar13: 1 ghz band centered at 6500 MHz
• 16mar13: 1 Ghz band centered at 7500 MHz.
• Mock spectrometer.
• 86MHz Bandwidth * 14 bands
• 1 second integrations
• 300 second scans (at least those with the rfi).
• The telescope was tracking sources and off positions
• 11mar13: peak rfi az=109.3,za=18.5 deg
• 16mar13: peak rfi: az=181.2, za=5.1 deg.

Dynamic spectra of 86MHz bands with rfi:

• 11mar13 6990 band (.gif)
• The large rfi starts around 60 seconds and last for about 10 seconds
• there is a precursor at 40 seconds.
• the dynamic spectra has been normalized to the median spectra.
• This is why there is a brighter stripe where the rfi was on for ashorter period of time.
  
• 16mar13 7012 band (.gif)
• The rfi starts around 70 seconds.
• There looks like a weaker set around 270 seconds.a2765cbh.pro

Line plots of rfi:

• Page1 : time variation of the rfi.
• 11mar13 rfi. average 6980-6985 MHz and then plot versus time.
• frame1: full scale
• frame2: blowup in time and amplitude
• The strong rfi lasts for about 8.6 secons
• there is a precursor about 23 secs before the strong rfi
• 16mar13 rfi. average 7020-7025 and then plot vs time
• frame 3: full scale
• frame 4: blowup
• The strong rfi lasts for about 18.8 seconds
• The rfi on the 16th was about 10 times weaker than the rfi on 11mar13.
• Page 2: rms/mean for the 300 seconds of each scan, covering the 1ghz bands
• Red in polA, green is polB
• Top frame: 11mar13 with rfi 6900 -> 7000+
• Bottom frame:16mar13 with rfi 6980->7050
• Page 3: overplot the spectra with the strongest rfi for both days.
• Each spectra was normalized to the median value for the scan
• the red,green traces were taken on 11mar13
• The blue,purple traces come from 16mar13
• The veritical dotted lines are placed every 19.43 MHz.
  
• The "on freq" is 13.00 MHz wide, the "Off freq" is 6.43
• The  "off freq" period is about 1/3 of the cycle.

• The spectra are normalized to Tsys and plotted with offsets for display
  
• 11mar13 spectra during rfi (.ps) (.pdf)
• 16mar13 spectra during rfi (.ps) (.pdf).
  

Summary

• rfi was seen in the cband hi reciever on 11mar13 and again on 16mar13
• The rfi covered 6900 to 7050 MHz (each day covered a part of the range)
• The rfi was on for:
• 11mar13: 8.6 seconds. It had a precursor about 23 seconds before the main rfi
• 16mar13: 18.8 seconds. The same around appears about 200 seconds later (but much weaker).
• The rfi has a period of 19.43 MHz
• 13MHz on
• 6.43 MHz off
• The off Freq is about 1/3 of the period.
• This periodic rfi was seen back on 25sep12.
• See the Dynamic spectra for the CW swing at 6974 MHz.
• Looking at the FCC allocations,
• Non Federal table:
• 6875-7025: .. (note NG is Non Government).
  
• FIXED NG 118
• FIXED-SATELLITE (Earth to space), (space to earth)
  
• MOBILE NG171