Radio interference

[JB 3.2]

I know you should listen to the glorious engine rather than music but........ The stereo in my car suffers from interference. Now here is the strange part, with the engine off there is very slight interference but as I move the key towards the ignition the interference gets considerably worse. This is before the key is even in the ignition or the ignition switched on. I've checked the leads on the stereo and the lead into the aerial amplifier and I've changed the actual stereo. Any ideas?

 

[Mark Elder]

John,

Do you need the key in your hand to induce this effect or does the interference get worse just moving your hand toward the ignition? It really does sound like a poorly screened aerial lead/connection. As you move around you are helping or hindering the signal (either the broadcast signal or the interfering signal). My bedside radio has same problem - when I lie in bed I get interference, when I move to adjust the aerial the interference goes away, very frustrating.

I'd be tempted to replace the entire length of cable from the windscreen connector to the radio (and maybe the signal amplifier).

 

[JB 3.2]

I'm still trying to resolve the issue of interference on the stereo system, and as Mark suggested there appears to be a fault in the aerial lead itself where the plug and coax cable are joined.

Can anyone offer any guidance on where to get a new lead from and how it is fitted at the amplifier end?

 

[geolab]

looks like you have an amp, and with amp there is coaxial cables.
Now what you need is the AUX out cables that go to the amplifier.
If your unit has coaxial out, easier, or the coaxial connections is on amp.

solution: wherever the coaxial connections are, (on unit or on amp) , strip the ends of 4 wires from the coaxial connections to the radio.
now unplug each rca and introduce a bit of stripped wire on the outer metal part of the plug, and replug the rca to catch the wire.
Do this to all four rca's.
now the other end of the four wires should reach the radio unit, attach the four stripped wires together and connect them to the units metal case (ground)
no more interference
regards

 

[JB 3.2]

Interesting thoughts Geolab, as far as I'm aware I don't have a separate amp. just a normal stereo head unit, but I will try running an earth to the unit.

I've replaced the DIN to ISO converter on the aerial lead and replaced the DIN plug itself, not an easy job as the centre wire is very thin and difficult to solder. This appears to have made some improvement but its still not right. I've also removed the ariel amplifier and checked for continuity and voltage. I was going to replace the complete aerial lead but this looks quite difficult at the amplifier end.

My next step is to reluctantly replace the amplifier itself which I suspect will include the lead. I'm also wondering if there is a break in the aerial lead between the amplifier and screen, I had a new screen fitted about 12 months ago which seems to coincide with this problem, but its very difficult to determine if this is the cause.

 

[Porker993]

ORIGINAL: JB 3.2

I had a new screen fitted about 12 months ago which seems to coincide with this problem,

As you know, the aerial joins to a tiny wire running around the windscreen, so, that is where I would start looking. Have the windscreen monkeys trapped it, or broken it ?

 

[Mark_Bennett]

ORIGINAL: geolab

looks like you have an amp, and with amp there is coaxial cables.
Now what you need is the AUX out cables that go to the amplifier.
If your unit has coaxial out, easier, or the coaxial connections is on amp.

solution: wherever the coaxial connections are, (on unit or on amp) , strip the ends of 4 wires from the coaxial connections to the radio.
now unplug each rca and introduce a bit of stripped wire on the outer metal part of the plug, and replug the rca to catch the wire.
Do this to all four rca's.
now the other end of the four wires should reach the radio unit, attach the four stripped wires together and connect them to the units metal case (ground)
no more interference
regards

I'm going to have to admit I can't quite follow this... which 4 wires?

 

[geolab]

any electrical wire you can find, split speaker wires will do well.
The idea is to ground the (neg) speaker out to the chassis of radio.
I had a whine in my car for 7 years, even with radio off (but amp on-always)
that was the only solution that worked for me
cheers

 

[JB 3.2]

I agree Mark especially as I asked them to do the screen twice as I wasn't happy with the first fit, but very difficult to prove this is the fault.

 

[Porker993]

It's a real pain, and I'm not sure what the answer is, short of taking it out and re-fitting it. (Again)

Maybe ring a (reputable) windscreen fitter and see what is their take on it.

Good luck.

 

[JB 3.2]

Just a quick update for anyone who may have similar problems. I've connected a piece of wire about the same length as the aerial in the windscreen direct into the aerial amplifier and get excellent reception on FM, AM and LW which seems to confirm problem does lie with the screen.

Having subsequently spoken to the guys that fitted the windscreen, plan is to take the car down there and connect the aerial lead to another screen which is not in the car but will rest on the seats. If reception is OK they have agreed to replace the screen.

 

[Mark Elder]

John,
While I can't think of a better plan, I suspect that a screen/aerial sitting on seats inside the car (shielded by bodyshell) might perform no better than a screen with a broken aerial in a position where it has good access to the radio signal. So it might fail the test even though it is the solution.

Could you put the aerial cable though the bulkhead gromet and over the rubber bonnet seal at the back of the bonnet so it can be connected to the new screen with a couple of people holding screen in approx correct position?

Hope you find solution - this must be very frustrating!

 

[JB 3.2]

Valid point Mark,

I will look at a few different options, objective was to keep the length of wire between aerial amplifier and screen as short as possible so it does not act as an aerial itself.