70cm QRM

A friend of mine in Cambridge Richard G3TFX is getting QRM on the GB3OV repeater. OFCOM cannot help.

He writes:

Can anyone pin down the direction of a pulsing telemetry signal causing QRM on the OUTPUT channel of the St Neots repeater GB3OV, 433.125 Mhz? It's a pretty strong signal in the center of Cambridge and my guess is it might be a device on a crane.

Bird migration and man-made electronic noise

See http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13290.html .

Evidence that bird migration is affected by human EM noise pollution - article in Nature journal.

MF "swish, swish, swish" interference

In recent months I've been suffering from man-made noise on MF which was not there before. I've a constant S8 noise floor now (it was around S1-2 before) and as I tune from 300-500kHz I get a rapid  "swish swish swish" every few hundred Hertz. I think there are frequencies where it is stronger but the new 472-479kHz is BAD, although I still manage WSPR decodes from DK and SM. For CW it would be just about impossible.

Now, I haven't yet tried to systematically work out what this is yet and nor have I tried a small external loop on RX or an E-field probe down the garden.

Before I start to investigate, does anyone have a clear idea what this rapid "swish swish swish" QRM is likely to be? I don't think the source is in my own house and on one side the neighbour's house is currently unoccupied. I have tried the obvious (turning off lights and SMPSUs in my own place) with no success.

Any knowledgeable help would be much appreciated.

Man-made interference at MF and LF is a critical consideration for newcomers. I hope that a new version of the RSGB book "LF-Today" (if one is planned) will give some information on how to search out such sources and some strategies for how they might be mitigated.