cband RFI measurements.

last updated 30jul19

30jul19:  cband plane altimeter looks like an frb.
26feb19: cband 4-5 ghz rfi,  azswings done 07feb19.
21jan19: 4250 rfi seen from the 12meter location.
16aug16: cband azswing covering 4715-5486 Mhz
09aug16: scanning the U-NII (5.15-5.85) band for out of band emissions
08aug16: cband azswing covering 4715-5486 Mhz
28jun16: cband azswing covering 4715-5486 Mhz
29jan16: radio redentor tower test: turning off,on cband internet providers
19jan16: road trip to radioRedentor tower. rfi below 5150 Mhz.
18jan16: 5ghz rfi from the 12meter site.
13jan16: cband az swing. 5ghz rfi.
02dec15: 5015-5055 rfi looking from 12meter
20apr14   p2865 cbamd run 4-5 ghz on 13apr14 shows avg and rms spectra
27mar14: 5030-5070, 5070-5100  rfi from yiyi's tower
05jun13: 5-6 Ghz on the telescope after rfi turned off.
04jun13: 2nd trip to yiyi's tower. Source of 5020 rfi.
31may13: 5020 Mhz rfi coming from yiyi avila's tower.
11apr13: 4920 rfi present 06apr13-09apr13.
27mar13: 6900-7050 rfi seen 11mar13,16mar13 by chris salter
25sep12:cbandHi azSwings using 6-7 Ghz
28aug12: azswings 5-6 ghz.
28aug12:5275 xpernet test from jonathan friedman's house
21mar12: 5990-6020 microwave link interference.
30sep11: 6580-6610Mhz rfi cbandhi
24sep10: 5670 MHz rfi.

21jan19: 4250 Mhz rfi from 12meter location.

    The hilltop monitoring system has been showing strong rfi at 4034-4150  and 4217 to 4327 for many years (and chris and tapasi were reporting problems at cband for probably just as long!).
Looking at the fcc allocation page,

   (fixed microwave)
fixed satellite (space to earth)
aeronautical radionavigation.

The first plot shows the 1 minute peak hold from the hilltop rfi monitor during our measurements (.ps) (.pdf)

On 21jan19 felix and I went to the 12meter location to see if we could get a bearing for this rfi.
The setup was:

    We mounted the antenna on a camera tripod and then took measurements at various magnetic bearings.

The plots show the average and peak hold spectra (.ps)  (.pdf)

A uls search of licensed operators between 4000 and 4500 Mhz within 50km of AO showed a prtc tower using 4070.


processing: x101/190121/  

18jan16: rfi below 5150 Mhz from 12 meter site

    on 18jan16 dana and i went to the 12meter site to check on the rfi below 5150 Mhz.
The plot shows what we saw at 5ghz (.ps) (.pdf):

processing: x101/160118/

02dec15: 5015 - 5055 rfi measured at 12meter

    Dana and i took the cband helix antenna  and the anritsu up to the 12 meter to look for the 5 ghz rfi that has been seen in the telescope (yet again).
The anritsu setup was:

    When pointing the helix we got a strong signal at magnetic bearing 155M (this is approximate, i did not use the compass and the antenna simultaneously). We had thought this was coming from yiyi's tower.. but his tower has a magnetic angle of 189 deg (from the 12 meter).
    The plots show the strength of the signal (.ps) (.pdf)

The lat/long table shows some local tower locations and bearings... none match this (although i should probably redo the compass measurement  lining the compass up while i'm pointing the antenna.

processing: x101/151202/

27mar14: 5030-5070, 5070-5100 rfi from yiyi's tower

The U-NII (Unlicensed National Information Infrastructure) band is used by wifi providers. It  covers:
    Observers reported rfi  between 5030 and 5070 in mar14.

Timeline for rfi:


processing: x101/140327/

06apr13: 4920 rfi appears for 4 days (top)

    Rfi at 4920 MHz (+/-4,5 MHz) appeared on 06apr13 and remained continuously on  until 09apr13.

On 08apr13 time domain data was taken with the mock spectrometer. The setup was:

the dynamic spectra shows 250 millisecs of spectral data with .154 millisecond resolution (.gif)
The plots show the average spectra as well as total power vs time (.ps) (.pdf)
The hilltop monitoring plots show when the birdie came and went:


processing: x101/

28aug12: 5275MHz Expernet test from Jonathan Friedman's house. (top)

    Expernet (xairnet) delivers wireless internet:

Jonathan friedman is installing the service at his house (about 1 mile from ao). We did a test on 28aug12 to see how the service affects the cband system. The setup was:
Dynamic spectra were made during the transfers for each of the 7 bands:
The plots show the strength of the signal (.ps) (.pdf):



21mar12: rfi 5990 - 6020 Mhz rfi (top)

    Chris salter reported rfi at 5990 to 6020 Mhz using the cband receiver. This is getting in the way of a red shifted line of OH??
The plots show an example of the rfi (.ps) (.pdf):

Looking through the rfi database (searching by geographic location and frequency range) i found:


Processing: x101/120317/

30sep11: rfi 6580-6610 Mhz cband hi  (top)

    Rfi was reported in cband high on data taken 30sep11.. It covered 6580 to 6610 Mhz. This rfi had been seen before back in jun11.

The plots show the rfi from a 300 second "on source" observation (.ps) (.pdf):
Dynamic spectra for 300 seconds of data (.gif):

Source of rfi:

processing: x101/110930/

24sep10: birdie around 5670 (top)

   Rfi has appeared at 5670 MHz
the first plot shows the data in the cband receiver (.ps) (.pdf)
the second plots shows Hilltop monitoring data with 8 MHz about ieee802.11 channels (.ps) (.pdf)


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