Satellite Internet forum

Satellite Internet forum
https://www.satsig.net/cgi-bin/yabb/YaBB.pl Anything else >> General and other topics >> Satellite interference : help please https://www.satsig.net/cgi-bin/yabb/YaBB.pl?num=1611840718 Message started by Admin1 on Jan 28^th, 2021 at 1:31pm

Title: Satellite interference : help please
Post by Admin1 on Jan 28^th, 2021 at 1:31pm

Can anyone say what is the C band interference here:

https://www.youtube.com/embed/3Z_EYovfSzA

Ideas/analysis to eric@satsig.net please

Title: Re: Satellite interference : help please
Post by Nimrod Kapon on Jan 28^th, 2021 at 9:00pm

I would say a radar, though it could be also harmonics caused by saturation.

Having another video clip with faster sweep will allow to determine better.

Nimrod

Title: Re: Satellite interference : help please
Post by Admin1 on Feb 6^th, 2021 at 1:15pm

I'm not sure if they have found the problem or resolved it yet.

Full span interference plot LNB 0 to 3 GHz.

A local 5G source is suspected but it could be a rotating radar if it peaks up every 10 seconds or so at some frequency well away from wanted carrier and the high level is causing whole LNB to saturate, the noise floor to increase and intermod spurii to appear all over the place.

It is difficult to explain how to tune a spectrum analyser to the interferer, set a suitable RES BW and then use zero span to observe radar rotation and pulse rate with different sweep times. Single sweep helps also, with averaging OFF.

Does anyone else (other than me!) try taking the LNB/feed off the antenna and pointing it around in azimuth (held in your hands) to find the source direction of terrestrial interference transmissions like radar, WIMAX and 5G or whatever.

Not finished yet.
Eric

Title: Re: Satellite interference : help please
Post by Nimrod Kapon on Feb 6^th, 2021 at 8:02pm

Hi,

Setting the spectrum to zero span will allow to identify the cycle of the interferences. It could be a radar, as well as TDMA signal..!

I also remove the feed with LNB connected and walk around pointing to different directions, as good a horn antenna.

Title: Re: Satellite interference : help please
Post by Admin1 on Feb 7^th, 2021 at 11:49am

Good to hear that. I am pleased to find someone else doing the same thing. I used to tune to a TDMA return channel, set the RES-BW the same as the bursts and, in zero span, watch what was happening. I managed to identify individual remote VSATs that were low level or distorted with abnormal amplitude shape and also intermittent interfering cross-pol TDMA bursts from a remote site in a network operating on the other polarisation.

Added 12 Feb 2021..
Here is a link to a good range of C band filters to block interference from 5G, radar, WiMax etc.
C band filters

If anyone finds this useful please say. Thanks.