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
center Freq	bandwidth	notes	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

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