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Radio noise suppression


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#1 trfella

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Posted 18 November 2008 - 02:17 PM

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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#2 Mike Collins

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Posted 18 November 2008 - 03:03 PM

Where is the arial? If it's in the front wing it could be radiated noise from the HT side. You could try a flexible earth strap on the bonnet hinge. Plug leads ok? Supressors in plug caps?
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#3 trfella

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Posted 18 November 2008 - 03:19 PM

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, 18 November 2008 - 03:25 PM.

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#4 Mike Collins

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Posted 18 November 2008 - 03:36 PM

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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#5 trfella

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Posted 18 November 2008 - 03:59 PM

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.
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#6 Goswell

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Posted 18 November 2008 - 05:54 PM

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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#7 trfella

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Posted 18 November 2008 - 06:13 PM

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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#8 Mike Collins

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Posted 18 November 2008 - 06:48 PM

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

That's a quick and easy thing to try.

Does the noise change if you open the the bonnet? If the bonnet is not well bonded to earth it could act as a transmitting arial.
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#9 johnny250

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Posted 19 November 2008 - 11:59 AM

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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#10 trfella

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Posted 19 November 2008 - 12:10 PM

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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#11 Jersey Royal

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Posted 19 November 2008 - 12:41 PM

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.crutchfie...l...=1&page=all

Hope you get to the bottom of it

Cheers

Guy

Edited by Jersey Royal, 19 November 2008 - 12:41 PM.

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#12 Goswell

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Posted 19 November 2008 - 01:00 PM

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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#13 88V8

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Posted 19 November 2008 - 01:11 PM

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

:blink: It does? :unsure:
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#14 stuart

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Posted 19 November 2008 - 01:15 PM

News to me as well :blink:
Stuart.
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#15 trfella

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Posted 19 November 2008 - 01:22 PM

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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#16 Jersey Royal

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Posted 19 November 2008 - 01:26 PM

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.distribut...rotor_arms.html

Cheers

Guy
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#17 trfella

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Posted 19 November 2008 - 01:49 PM

I would recomend Martin Jay at

http://www.distribut...rotor_arms.html

Cheers

Guy


Thanks for that Guy :)

Looks like I have a repro arm and cap as I cannot see any manufacturers stamp on them. Condition is good and the carbon brush is ok, but I think it best to replace them too.
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#18 trfella

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Posted 19 November 2008 - 02:02 PM

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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#19 johnny250

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Posted 19 November 2008 - 05:02 PM

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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#20 Mike Collins

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Posted 19 November 2008 - 05:29 PM

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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