G3LVP wrote:After a few months through the summer the 'Sweeper' which I've reported in the past has now moved down the band from the FM section to sweep over the SSB section sweeping from about 70.180 to 70.230 at a rate of about 1 c/s, this signal is present 24 hrs. a day.
When I beam towards the source (SE) which appears to be in an area of houses about 4 - 800 yds. away it's S9+10. In spite of walking round with a scanner I've not managed to pin the source down.
There are at least two more of these sweepers which I can hear around 67.63 & 70 97 (in the band used by Fire & Rescue), way down on 20.86 there's another at around S4. These sweepers all have similar sweeping characteristics and are all T3 modulated by 50 c/s mains hum. They don't appear to be directly related either harmonically or exact sweep rate.
As the temperature is only a chilly 3 deg. C. this morning I assume that the source which I hear on 4m is affected by temperature and as the WX warms up hopefully it will drift back up the band.
Whilst there's not much hope of getting these annoying QRM sources turned off (imaging knocking on 'Joe Bloggs' door to ask what electronic kit he has....I'm conducting a survey!) I'm really curious to know what devices causes this QRM, they obviously aren't intended to radiate and can't be compliant with EMC regs.
Surely this is not the only area where these things can be heard? I would be very interested to hear any reports of similar signals.
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