# cb az swings, 5ghz rfi  08aug16

#### 14aug16

During jul16, angel and israel used the unii band scanner to identify some of the out of band transmitters in the UNII band.
Two cband azswings were done  on 8jul16 to see how thing looked through the telescope cband receiver,.

The setup was:
• az 270-630 and back at +/- .35deg/sec
• clear weather
• dome at za=18deg
• mock spectrometer with 7 boxes spaced by 100 MHz.
• cfr: 4800,4900,5000,5100,5200,5300,5400
• 4715 to 5486 MHz  covered
• 172MHz bw, 8192 channels per box, 1 second sampling
The data processing for each board
• input the data averaging to 1 second
• average pola and b.
• interpolate az positions to center of data records.
• For dynamic spectra
• compute median band pass, divide this into all spectra
• find rfi free section of band, compute median value  for each spectra and then divide each spectra by these values
• For rfi bands:
• looking at the dynamic spectra:
• find the center and bandwidth of each rfi band
• also find the non-overlapping portion of the rfi band (many rfi bands were overlapping).
• compute the total power in each rfi band using the non-overlapping portion of the rfi band.
• plot this total power vs az for the CW and CCW az swings.

## Dynamic spectra:

The images show the dynamic spectra for the Clockwise (CW)  az swings:

 Center of band range 4800 MHz (.gif) 4714-4886 4900 MHz (.gif) 4814-4986 5000 MHz (.gif) 4914-5086 5100 MHz (.gif) 5014-5186 5200 MHz (.gif) 5114-5286 5300 MHz (.gif) 5214-5386 5400 MHz (.gif) 5314-5486

## Birdie power vs azimuth.

I also plotted the rfi power vs az position for the non-overlapping portion of each rfi (.ps) (.pdf)
• Each rfi was plotted in a different color with an offset for display purposes
• For each rfi, the CW and CCW az spins were overplotted
• The CW and CCW swings were spaced by at least 20 minutes...
• most of the rfi bands show a repeatable azimuth dependence.
• This means that the rfi is coming from a stationary azimuth direction
•  (not necessarily the azimuth of the peak since the scattering into the dome can be complex).
• Some of the rfi's look to have similar azimuth peaks.. that means they are probably coming from the same tower
• many of the rfi's have unique azimuth peaks.
The table shows the rfi bands that were found:
Frequencies with common colors, have similar  azimuth dependence

 center Freq bandwidth notes unii scanner devNm date 4750 wideband strong, covers 4710-4800 narrow az dependence about -25 degs. 4930 20 DM-AP Cerro-12 160811 160812 4950 20 weak 4960 10 weak 4977 5 4985 10 4995 10 5010 20 DM AP2 Maricao2 160809 5015 20 vp.net hq tower utuado . from 30jun16 field trip it was very strong. This strong signal is now gone. There is still a weak signal (probably from another tower). It is difficult to get a direction because it overlaps  adjacent transmissions. 5030 10 toward radio redentor, strong 5065 20 5110 20 no name 160811 160812 5120 20 dir about 220deg. no plot since confused  with adjacent emissions. DM AP  Cerro 11 160809 160811 160812 5140 20 new-gt-ca-paj- AP Orocovis o Not seen 160809 160811 160812 5150 10 toward radio redentor strong vivi.net radio redentor tower (from field trip 30jun16)

## Summary

• there are about 14 rfi bands in the 4715 to 5150 portion of the band
• The rfi's repeat in azimuth (spaced by  over 20 minutes). So they are coming from a fixed azimuth location (they are not just time variable).
• Some of the rfi's have similar rfi dependence.. these are probably coming from the same towers.
• The unii scanner sees some of these emissions.
• the strong 10 Mhz emissions are not seen by the unii scanner. Th

processing: x101/160808/azswing_cbinp.pro, azswing_cbplot.pro

rfi measurements home
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