5020 MHz rfi in cband


01mar13: 5020 rfi in a2765 data
hilltop rfi  monitor sees the rfi appear
Searching for the source of the rfi.
24may13:looking for the rfi  from the platform
30may13: trip to within 2 km of yiyi avila's tower
04jun13 : 2nd trip to yiyi avila's tower. Stations causing the interference.
04_05 jun13: hilltop data shows when things turned off.
05jun13: 5-6 Ghz band. How it now looks on the telescope


 Intro: (top)

    Various projects (a2765, a2334) reported interference at 5015-5025 MHz. This frequency range is also used for vlbi observations.
 The fcc allocation database has:
We would expect to start seeing rfi at 5150 and above due to the RF devices.

To investigate this rfi:

01mar13: 5020 rfi in a2765 data. (top)

    A2765 was doing double position switching with the mock spectrometers. The channels widths were 10 Khz.
The dynamic spectra shows 300 seconds of data measured on 01mar13 (.gif)
The average spectrum for the 300 second image is also plotted (.ps) (.pdf):
processing: x101/130301/cbrfi5020.pro

Hilltop rfi monitoring sees the rfi appear.  (top)

        The hilltop monitoring records a 60 second peak hold on the 5000-6000 MHz band every 19 minutes.

The first plots shows 20MHz total power about 5020 MHz for 01jan13 thru 01may13 (.pdf):
The 2nd set of plots shows The average spectra for each day : 10feb13 through 05mar13 (.pdf).
The 3rd set of images show dynamic spectra for 10feb13 through 05mar13 (.pdf):
processing: x101/130316/hilltop.sc

24may13: looking for the rfi from the platform.  (top)

    The anritsu spectrum analyzer was taken to the platform with the cband helix to search for the direction of the 5020 rfi. Nothing was seen (even with the preamp on).
On 24may13  an amplifier right next to the helix antenna. The chain was then: helix, amp, cable, anritsu spectrum analyzer (with preamp on).

30may13:1st trip to yiyi avila's tower:

    On 30may13 dana and i drove out to within 2 km  of yiyi avila's tower in the rfi van.
the plots show the strength of the rfi close to the tower (.ps) (.pdf):

processing: x101/130530/rfivan.pro

04jun13: 2nd trip to yiyi avila's tower.

    On 04jun13 angel and i drove out to yiyi avala's tower. We arranged to meet the tower engineer at the site. We used the anritsu spectrum analyzer for the measurements. Its setup was:

The plots show the rfi in 5000 to 5200 MHz (.ps) (.pdf):
processing: x101/130604/rfivan.pro

04,05jun13: hilltop monitor data shows rfi turning off.

    The hilltop rfi monitor data was examined to see when things got  turned off:

processing: x101/130604/hilltop_04jun13.pro,hilltop_05jun13.pro, hilltop.sc

05jun13:cband 5-6 Ghz on the telescope after rfi turned off.

    On 05jan13 400 seconds of data was taken with the cband  receiver using the mock spectrometer. 5 to 6 Ghz was covered. The setup was:
The first plot show the average, average/fit and rms/mean for the entire 5-6 ghz band (.ps) (.pdf)

    The table shows the dynamic spectra and 400 second averages, rms/mean for
    each 172 MHz band
Avg,rms spectra
dynamic spectra
(.ps) (.pdf)
(.gif) 5130,5145 illegal internet comm.
legal unlicensed band starts at 5150
(.ps) (.pdf) (.gif) more internet comm. using U-NII band
(.ps) (.pdf) (.gif) U-NII band stops at 5350
5415 rfi may be illegal
(.ps) (.pdf) (.gif) U-NII band starts again at 5475
5468 edge of rfi may be illegal.
most of these are internet comm.
(.ps) (.pdf) (.gif) more internet comm.
(.ps) (.pdf) (.gif) 5790-5800 very large rfi.
U-NII band stops at 5825.
(.ps) (.pdf) (.gif)

processing: x101/130605/cbrfi.pro

Summary:  (top)

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