New Interference Source

Noise and interference issues?
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daveB
Posts: 1006
Joined: 07 Oct 2014 16:49

New Interference Source

Post by daveB » 18 Nov 2017 18:49

This screen shot shows the interference plaguing my reception at the bottom of the FM Band - it appeared at the beginning of November and apart from a few breaks appeared to be 24/7. (This is in addition to the solar light interference after dusk).
89MHz severe interference.jpg
I was able to establish it was emanating from the East and suspected a PLA device. Using a PL380 portable I went 'fox hunting' and found what I believe to be source. An old X reg motor vehicle parked in the service road behind our row of houses. It happens to be an end terrace with a public footpath beside it so I could move close the house it belongs to prove the interference dropped away as I moved away from the vehicle/towards the house.

I am not yet 110% sure it is the culprit - but late last night the interference suddenly stopped - and the car parked on the corner was gone. It was there this morning - so was the car. Late this afternoon the interference was gone - so was the car. This is the spectrum. Note the strength of the interference either side of Radio 2 on 89.1 around 18 m (hor) from the vehicle (6 m vert).
89MHz Vert no interference.jpg
So what could the source be - I can't see that it an mp3 FM transmitter - I've had them before, but as a single discrete channel. I wonder if it could be an insurance company's 'blackbox'?

If the car is the source of the signal - which peaks at over 50 dB on the PL380 whip antenna -could it cause interference harmful to other road users (never mind it killing Radio 2 as it passes other vehicles).

Comments would be welcome.
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

daveB
Posts: 1006
Joined: 07 Oct 2014 16:49

Re: New Interference Source

Post by daveB » 24 Nov 2017 22:17

It's the car!! When there is no interference I check for the car - it is not there. When it is there I have interference. But the car was away for over a day and when it came back I had a single strong signal around 89.0. Went out with the portable and it showed 67 dB about 1 m from the rear - so curiouser and curiouser.
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

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John Faulkner, Skegness
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Joined: 19 Sep 2014 15:55
Location: Skegness, Lincolnshire. JO03dd
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Re: New Interference Source

Post by John Faulkner, Skegness » 26 Nov 2017 11:20

Interesting stuff Dave. I have been checking out my locality with a portable MW radio and the noise situation here is also getting curiouser and curiouser. I might post in a separate thread.

Hope you can get to the bottom of this and get it sorted.

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