cb az swings, 4-5GHz rfi  07feb19


Data from the hilltop rfi monitor
azswing data processing
dynamic spectra
peak hold spectra for each az swing.
birdie power vs azimuth

Previous azmiuth swings:
16aug16: cband azswing covering 4715-5486 MHz
08aug16: cband azswing covering 4715-5486 MHz
28jun16: cband azswing covering 4715-5486 MHz
13jan16: cband az swing. 5GHz rfi.

rfi hilltop monitor spectra during the 6 azimuth swings (.ps) (.pdf)
Plots of total rfi hilltop monitor power vs date for the different rfi bands (.pdf)   (3.9MBytes)
dynamic spectra entire 4-5 ghz each az swing
dynamic spectra for each 160Mhz mock band for each az swing
the peak hold spectra for each swing (.ps) (.pdf)
plots of average rfi power vs azimuth for different rfi bands (.ps)  (.pdf):
FCC frequency allocation table  for 3500-5000 MHz (.pdf) 
Commercial point to point microwave licenses
Locations of transmitters in pr (lat,long, bearing from ao.

 Intro: (top)

       Strong interference has been seen in the 4-5 Ghz band. Data taken with a spectrum analyzer from the 12meter hill showed some of this rfi (more info).
Azimuth swings (on the 305m telescope) were done on 07feb19. The setup was:

Data from the rfi hilltop monitor. (top)

    The rfi  hilltop monitor uses filters, amplifiers, switches, and a spectrum analyzer to monitor the rfi environment from DC to 10Ghz.
The frequency range is broken up into 20 separate frequency bands.

The first plot shows the 1 minute peak hold spectra during the 6 azimuth swings (.ps) (.pdf)

Plots of total power vs date for the various rfi (.pdf)

The azswing data processing for each board (top)

    For each azimuth swing the following processing was done:

The az swing dynamic spectra: (top)

All frequency bands in 1 image:

    There are two images in each file.

azswing (CW then CCW)
high sensitivity
Low sensitivity  
azswing 1
 (.png)  (.png)
azswing 2
 (.png)  (.png)
azswing 3
 (.png)  (.png)

1 freq Band per image

Band range [MHz]
swing 1
swing 2
swing 3
3995-4144 .gif .gif .gif
4145-4285 .gif .gif .gif
4285-4425 .gif .gif .gif
4425-4565 .gif .gif .gif
4565-4705 .gif .gif .gif
4705-4845 .gif .gif .gif
4845-4995 .gif .gif .gif

Peak hold Spectra for the azswings (top)

    For each CW or CCW azswing

the plots show the peak hold spectra for each swing (.ps) (.pdf)

Average birdie power vs azimuth. (top)

    From the peak hold spectra, a number of frequency ranges stick out. The average total power over these frequency
ranges was computed and then over plotted for each of the azimuth swings. When multiple swings overlap in azimuth,  the
transmission is coming from a fixed direction (and is not very time variable). The azimuth used is from the azimuth encoder, it is not necessarily the
heading for the transmission (it depends on how it scatters into the dome optics).

plots of average rfi power vs azimuth for different rfi bands (.ps)  (.pdf):

-55 to +12
add 180deg
125 to 192
This is part of the micro wave link band.
Transmissions should be 20 MHz each.
az position is repeatable

The az location is not repeatable.
This covers the radio altimeter band used by airplanes
-30 to -5
add 180deg
150 to 175
az position is repeatable
probably also part of 4750-4800 mhz
-8 to -3
add 180deg
172 to 177
az position is repeatable.
This may be part of the 4500-4700 MHz rfi.
125 to 135
add 180deg
305 to 315
repeats in azimuth but weak.
Looks similar to 10 MHz transmission seen before (at different freq).
The 10MHz transmission are not decoded by our uni scanner.

Summary/ what they could be. (top)

processing: x101/190207/azswing_cb/cbazswingrfi.pro, mk1band.pro azswing_cbplot.pro

rfi measurements home