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Radio noise suppression


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I'm at a loss!!

 

I have fitted a suppressor to -

 

ignition SW

alternator main output

alternator warning light output

 

Also installed an earth strap to the wiper motor gearbox and fitted choke at main power (off term 5 on ignition barrel)

 

Tried earthing the aerial, radio main chassis etc and I still have a clicking sound from the speaker when the engine is running.

 

Now, my car has a full Lumenition electronic ignition system - could this be the culprit?

 

The radio works fine when the engine is off, and is LW/MW only.

 

Any other suggestions, apart from covering everything in sight with foil?? ;)

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Hi Mike,

 

The aerial is mounted on the rear deck on the o/s. The ignition leads are silicone, and approx 5 years old - only covered a couple of thousand miles.

 

You think I need to install suppressors in the plug caps too?

 

Would you suggest 1k or 5k suppressors? I have seen the ends available with these built in, or should I go for something that fits into my existing cap?

 

ETA - With the engine running I get a lot of noise from the car on my television picture!!!

Edited by trfella
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I would think that the noise on your television confirms the problem is radiated RF from the high tension side.

 

In the early days of TV broadcasting, there was an 'advert', by the GPO I think, that featured an interference generating car and showed the TV screen. The viewer hurled a heavy glass ashtray throught the screen and the car blew up.

 

Are your leads copper conductors or carbon 'string' type? If you have multimeter you could measure the resistance of the leads to check, string types should be several Kohms.

 

If copper then you don't really have any HT supression. Is this a new problem or has it always been noisy?

 

I don't know which of the plug cap supressors would be better, either has to be an improvement on none though.

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Although it maybe impossible to fix completely I would run a dedicated earth wire to the base of the aerial.

Make sure the earth is hard wired through the car and does not rely on the bodywork.

Connect it to the fuel pump feed maybe.

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Although it maybe impossible to fix completely I would run a dedicated earth wire to the base of the aerial.

Make sure the earth is hard wired through the car and does not rely on the bodywork.

Connect it to the fuel pump feed maybe.

 

 

What if I connected the lead to the main battery negative from the base of the aerial?

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With the engine running I get a lot of noise from the car on my television picture!!!

 

Not only yours either..I bet you are popular as you drive down the street :angry:

Suggest you try and find and fix the source of the sparks (plugs?) rather than try and prevent your radio picking them up.

 

john

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Not only yours either..I bet you are popular as you drive down the street :angry:

Suggest you try and find and fix the source of the sparks (plugs?) rather than try and prevent your radio picking them up.

 

john

 

 

And this is my fault - a car I have only done 300 miles in since I purchased it in July this year?

 

I have only just noticed the problem, so don't appreciate the smart comments thank you!

 

I am dealing with it hence the posts on here for advice - ok? :angry:

 

The radio installation has highlighted the problem, otherwise it would have gone unoticed for some time. :blink:

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And this is my fault - a car I have only done 300 miles in since I purchased it in July this year?

 

I have only just noticed the problem, so don't appreciate the smart comments thank you!

 

I am dealing with it hence the posts on here for advice - ok? :angry:

 

The radio installation has highlighted the problem, otherwise it would have gone unoticed for some time. :blink:

Tr Fella,

 

Found this site , quite interesting

 

http://www.crutchfield.com/S-2FnKoH9fItC/l...=1&page=all

 

Hope you get to the bottom of it

 

Cheers

 

Guy

Edited by Jersey Royal
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Connecting direct to the earth side of the battery is ideal.

Lifting the bonnet will definately cause the interference to "Escape" as the bonnet as acting as a shield.

The bonnet has an earth bonding wire, worth a check.

Once helped a friend with a fibreglass car on which he had fitted tin foil under the bonnet to act as the shield, but as he hadn't bonded it to earth it didn't work.

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Thanks everyone.

 

It seems my silicone NGK KR31 leads are unsurpressed!!

 

I am looking into some Magnecor ones to replace, and whilst I'm at it I'll change out the plugs, dizzy cap and rotor arm.

 

Any preferences as to the cap and rotor arm, and where from? I'm guessing that OEM is the way to go as the repro stuff is pants - or so I have heard!

 

This ground strap on the bonnet - where would this be attached?

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Thanks everyone.

 

It seems my silicone NGK KR31 leads are unsurpressed!!

 

I am looking into some Magnecor ones to replace, and whilst I'm at it I'll change out the plugs, dizzy cap and rotor arm.

 

Any preferences as to the cap and rotor arm, and where from? I'm guessing that OEM is the way to go as the repro stuff is pants - or so I have heard!

 

This ground strap on the bonnet - where would this be attached?

 

 

I would recomend Martin Jay at

 

http://www.distributordoctor.com/rotor_arms.html

 

Cheers

 

Guy

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OK, dizzy cap, rotor arm AND leads ordered from Distributor Doctor. Apparently, the leads are better than the Magnecor ones.

 

Seems that the NGK leads I have fitted do not conform to EMC regulations :angry:

 

It has also been suggested that I install a suppressor to my Bosch fuel pump too.

 

Watch this space.... :blink:

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And this is my fault - a car I have only done 300 miles in since I purchased it in July this year?

 

I have only just noticed the problem, so don't appreciate the smart comments thank you!

 

I am dealing with it hence the posts on here for advice - ok? :angry:

 

I wasn't intending 'smart comments' what I meant was the source of the sparks should be found and surpressed, your plug leads as it's turned out, rather than running extra earthing wires, covering things in tinfoil etc.... :mellow:;)

 

john

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I would avoid changing everything in one go, HT leads first and check for improvement. If you scatter gun it and one part is poor, you will have to start again to find it.

 

It's very unlikely there is/was an earth strap an the bonnet hinge, you will have to make one out tinned copper braiding or similar and fit it under the hinge bolts. Clean the contact areas before fitting. If you need it.

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I wasn't intending 'smart comments' what I meant was the source of the sparks should be found and surpressed, your plug leads as it's turned out, rather than running extra earthing wires, covering things in tinfoil etc.... :mellow:;)

 

john

 

Then I apologise for over reacting. It was the angry face you posted that sent me over the edge you know ;)

 

I also thought you were implying that I was being selfish at fixing my radio problem, but ignoring the RF I was chucking out everywhere else.

 

I'm chilled :)

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I would avoid changing everything in one go, HT leads first and check for improvement. If you scatter gun it and one part is poor, you will have to start again to find it.

 

It's very unlikely there is/was an earth strap an the bonnet hinge, you will have to make one out tinned copper braiding or similar and fit it under the hinge bolts. Clean the contact areas before fitting. If you need it.

 

That was the plan Mike - to change everything one bit at a time and see what differences it makes.

 

I still don't get the bonnet strap. The bonnet is attached with bolts to clean metal to the front inner valance. That in turn is attached to the shell and welded. The whole lot is tied together if you see what I mean. I really don't see how adding a strap (and causing a potential future rust spot) is going to help, as technically the bonnet is grounded.

 

To prove a point I earthed a test light to the bonnet catch spring (I just replaced it the other month), and my bulb lit up.

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I'll check the leads and report back on here.

 

There was never a radio fitted to this car, so I decided to install one myself. I have only had the car since July this year.

 

Hi

I am intrigued why there are two wires to the plus side of the coil with a lumenition fitted, there should be only one.The red lead unless they have changed there colour scheme should be the power supply to the lumenition the purple lead should connect to the - side of the coil.

Regards

Neil

Edited by ntc
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The bonnet earth strap is probably a desperation measure and very likely not needed. But, the bonnet panel is earthed via the hinge pins, greased, corroded possibly and moving, the spring loaded catch at the rear is probably greased. All add resistance and at high frequencies things can look different from a DC measurement.

 

The important thing is to reduce the radiated field from the ignition system, with that achieved the prospect of the bonnet panel acting as an aerial should no longer be significant.

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Hi

I am intrigued why there are two wires to the plus side of the coil with a lumenition fitted, there should be only one.The red lead unless they have changed there colour scheme should be the power supply to the lumenition the purple lead should connect to the - side of the coil.

Regards

Neil

 

 

Oh no!! What now?

 

I'm beginning to realise I have bought a lemon :(

 

I have the white from the ignition switch, the red I don't know where that comes from. A brown dangling loose and would have been connected to the spare - terminal.

 

So you think this isn't wired up correctly?

 

I don't have any instructions for the ignition system, so have no idea what goes where!

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