# cb az swings, 5ghz rfi 16aug16

#### 08sep16

The previous cband azswing was done on 08aug16. Since then Angel contacted the fcc representative on the island as well as a number of the companies that were out of band.

On 16aug16 another set of cband azswings were done to see how things have cleaned up.. (looks like about 6 out of band emissions moved).

The setup was:
• az 270-630 and back at +/- .35deg/sec
• weather:
• light rain toward end of clock wise swing
• stopped raining during the ccw swing..
• 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 4767 wideband strong, covers 4710-4800 narrow az dependence about -25 degs. 4950 20 weak 4985 10 4995 10 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 5150 10 20 toward radio redentor strong vivi.net radio redentor tower (from field trip 30jun16) There also looks to be a 20 Mhz band on top of the 10Mhz band

## Summary

• there are about 9 rfi bands in the 4715 to 5150 portion of the band.. down from 14 on 08aug.
• This does not include some very weak rfi.
• 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: x101/160816/azswing_cbinp.pro, azswing_cbplot.pro

rfi measurements home
home_~phil