Medium Wave Interference.

Noise and interference issues?
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Zaaxx
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Joined: 18 Jun 2016 14:04

Medium Wave Interference.

Post by Zaaxx » 18 Jun 2016 14:48

First time poster here needs help.

I'm getting a very strong interference on medium wave between about 600-900 kHz.
It seems to be mains borne.
The fuse box is an old style Wylex type from the late 1960s

I switch off at the old fuse box or the circuit breaker that precedes it and the
interference disappears.
Great I think, now to narrow it down...
I switch on again and the interference is back on so I remove all the fuses from the
fuse box and the interference does not go away it is still there.
This problem started about 10 days ago.

So to recap, interference goes off when circuit is switched off at the fuse box or citcuit
breaker but stays on with it switched on when all fuses are removed.

When the fuses are removed and the interference is still there the electricity meter is not moving.

Is it possible that the circuit breaker is a double pole switch and removing the fuses only disconnects the live side of things?

Any ideas?

Thanks,
Mike (Perseus SDR, Wellbrook ALA loop)

Andrew Webster,Wigan
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Joined: 18 Sep 2014 16:03
Location: Wigan Northwest England
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Re: Medium Wave Interference.

Post by Andrew Webster,Wigan » 18 Jun 2016 15:53

Zaaxx wrote:First time poster here needs help.
I switch off at the old fuse box or the circuit breaker that precedes it and the
interference disappears.

Thanks,
Mike (Perseus SDR, Wellbrook ALA loop)
Hi Mike welcome to the forum can you tell me what is written on the circuit breaker that precedes the Wylex fuse box?
If it's a an isolator breaker or an ECLB it will be double pole switch the fuse box is also a double pole switch but the fuses only isolate the live side.

If you have an ELCB usually 100 ma that means your earthing via TT a stake in the ground to provide an earth for the property this system is usually for the supply coming from overhead lines.
It could just be and isolator between the meter and fuse box for isolating the supply so work can be done the on the fuse box without calling the district network operator (DNO) to pull the service fuse

Andy
Receiving equipment: 2 Sony ST-S311, 1 Sony ST-SE520, 1 Sony ST-SE700 2 crossed FM 5s rotatable, 1 homemade FM 3 horizontal beaming S/E, 1 vertical FM 3 fixed beaming at Ireland, 2 element band 1.

Zaaxx
Posts: 2
Joined: 18 Jun 2016 14:04

Re: Medium Wave Interference.

Post by Zaaxx » 18 Jun 2016 17:01

Here's the setup.


Image

Image

By the way I forgot to mention that the interference is intermittent.
It will come on for say 5 minutes then it will go off for 10 then come on again for say 8 minutes and go off for 3.

It is regularly random!

Andrew Webster,Wigan
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Joined: 18 Sep 2014 16:03
Location: Wigan Northwest England
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Re: Medium Wave Interference.

Post by Andrew Webster,Wigan » 19 Jun 2016 11:49

That switch is just an 100A isolator so no problem with that.
So the problem is intermittent and the QRM goes when main switches are off but still there with main switches on and fuses removed the only thing I can think of is damp or insects in the fuse box causing tracking but looking at the pictures it doesn't look damp insects however are conductive and can cause tracking.

So inside the fuse box from the main switch is a busbar (copper bar) which runs along the bottom of the fuse carriers and that's all.
One thing we have had is heavy rain showers lately but water damp would have be around the fuse box.

That's all I can think of.

Andy
Receiving equipment: 2 Sony ST-S311, 1 Sony ST-SE520, 1 Sony ST-SE700 2 crossed FM 5s rotatable, 1 homemade FM 3 horizontal beaming S/E, 1 vertical FM 3 fixed beaming at Ireland, 2 element band 1.

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John Faulkner, Skegness
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Re: Medium Wave Interference.

Post by John Faulkner, Skegness » 19 Jun 2016 12:02

A long shot .... Could somebody have hacked into the box and secretly put a feed to another device somewhere?

I have known these things happen.

satnipper
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Location: Western Europe

Re: Medium Wave Interference.

Post by satnipper » 19 Jun 2016 12:34

Is it a directly wired boiler or something which is firing?

Andrew Webster,Wigan
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Re: Medium Wave Interference.

Post by Andrew Webster,Wigan » 19 Jun 2016 12:52

John Faulkner, Skegness wrote:A long shot .... Could somebody have hacked into the box and secretly put a feed to another device somewhere?

I have known these things happen.
The only place a wire could connect in that fuse box is on it's main switch and trying to connect a smaller wire along with the meter tails would be difficult to do and then access to the front of fuse box would be required.
See link below scroll down to Wylex CU that shows the insides of the fuse box.

http://www.diynot.com/wiki/Electrics:hs_pic3

Andy
Receiving equipment: 2 Sony ST-S311, 1 Sony ST-SE520, 1 Sony ST-SE700 2 crossed FM 5s rotatable, 1 homemade FM 3 horizontal beaming S/E, 1 vertical FM 3 fixed beaming at Ireland, 2 element band 1.

Andrew Webster,Wigan
Posts: 1838
Joined: 18 Sep 2014 16:03
Location: Wigan Northwest England
Contact:

Re: Medium Wave Interference.

Post by Andrew Webster,Wigan » 19 Jun 2016 22:55

Just been thinking about this with the isolator or main switch off that means both live and neutral are disconnected but with the switches on and fuses out only live is disconnected neutral will be connected to the supply.
So it would seen that is where the QRM is originating from the supply cable thus the neutral wire acting as an aerial.

As to where the QRM originates from well just about anywhere that is connected to your supply cable.

Andy
Receiving equipment: 2 Sony ST-S311, 1 Sony ST-SE520, 1 Sony ST-SE700 2 crossed FM 5s rotatable, 1 homemade FM 3 horizontal beaming S/E, 1 vertical FM 3 fixed beaming at Ireland, 2 element band 1.

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