# cb az swings, 5ghz rfi  28jun16

#### 29jun16

Angel and Israel made field trips to yiyi avila's tower on 27 and 28jun16. They found :
• 5110 - 10MHz coming from yiyi's tower. It was DM wireless
• 4940 and 4950. from the tower, but pointing east. This was also DM wireless
• They had dm wireless change to legal frequencies.

On 28jun16 i did 2 azimuth swings to see what was left in cband rfi around the uni band.

The setup was:
• az 270-630 and back at +/- .35deg/sec
• clear weather then cloudy with a bit of rain, then clearing up no the ccw spin
• 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 4754 wideband strong, covers 4750-4800 narrow az dependence about -25 degs. 4950 20 weak 4960 10 weak 4977 5 4985 10 4995 10 5010 20 5015 20 strong vp.net hq tower utuado . from 30jun16 field trip 5030 10 toward radio redentor 5065 20 5110 20 5140 20 5150 20 toward radio redentor vivi.net radio redentor tower(from field trip 30jun16)

## Summary

• there are about 13 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.
• a number of the rfi's have similar rfi dependence.. these are probably coming from the same towers.
• form the 30jun16 field trip to radio  redentor/HQ towers we found the source of :
• the 5015 rfi (vp.net on hq tower in utuado).
• after many attempts at trying to change the freq (all attempts failed).. the operator turned off the signal
• the 5140-5160 rfi.. ViVi.net on radio redentor tower.
• angel talked to the owner of company.. He said he would look into changing it.
• The field trip also showed that the small dishes used by these companies are very directional. At the tower, we could not see the  signal if we were on the opposite side of the tower (away from the direction the dish was pointing), looking back at the tower.

processing: x101/160113/azswing_cbinp.pro, azswing_cbplot.pro, and similar routines in 160115.

rfi measurements home
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