Rf supression

[stan]

I could only find 1 ref to this subject but doesnt really answer my question?

So the car is original positive earth, I fitted a new isolated negative earth radio, swapping the aerial connections round also so I dont fry the radio.
I have fitted a filter box to the power supply leads which has helped remove some noise but still getting high frequency interference particularly when I accelerate but reduces when off the power?
The ignition leads look new as does the coil and I cleaned up contacts on coil, so is it noise from the ignition leads still or the dizzy or maybe the dynamo?

Any ideas?

[johnwp5bcoupe]

It is probably Dynamo Whine Stan the cure is a suppression Capacitor 1 to 3 Micro Farrad they were/are bolt on near the Dynamo

[stan]

Nov 13, 2017 12:11:25 GMT johnwp5bcoupe said:

It is probably Dynamo Whine Stan the cure is a suppression Capacitor 1 to 3 Micro Farrad they were/are bolt on near the Dynamo

Thank you John I did consider something on the dynamo? Is it just a bog standard capacitor or one made especially road and dirt proof?

[johnwp5bcoupe]

It should have from memory a slotted bracket to mount it and a Spade Lead

[stan]

Nov 13, 2017 16:57:49 GMT johnwp5bcoupe said:

It should have from memory a slotted bracket to mount it and a Spade Lead

Thanks seen them on fleabay presume no need to worry about it being positive earth dyno?

[Phil Nottingham]

My dad had a number of cars from the mid 60's to the late 70's and I always fitted the radios and the dynamo was always the 2nd item for suppression after the ignition, then the coil and then the wiper motor.  I still have a selection of the suppressors and I have one on the P5 dynamo and the P5B alternator  but not the P4 which does not seem to need anything

[stan]

Nov 13, 2017 22:10:28 GMT Phil Nottingham said:

My dad had a number of cars from the mid 60's to the late 70's and I always fitted the radios and the dynamo was always the 2nd item for suppression after the ignition, then the coil and then the wiper motor.  I still have a selection of the suppressors and I have one on the P5 dynamo and the P5B alternator  but not the P4 which does not seem to need anything

Ironically no other motor creates any interference, wiper and fan motor are fine. For the small pennies I will do the dyno and look at the dizzy, probably same thing? Just initial niggles I have to sort when a new (old) car ends up in my hands, I am old fashioned like stuff to work.

[johnwp5bcoupe]

Nov 13, 2017 21:59:39 GMT stan said:

Nov 13, 2017 16:57:49 GMT johnwp5bcoupe said:

It should have from memory a slotted bracket to mount it and a Spade Lead

Thanks seen them on fleabay presume no need to worry about it being positive earth dyno?

No its not polarity conscious

[stan]

Aaagh ! Depression not suppression.

So i fitted the capacitor to the dynamo last night no difference.

I checked the ignition leads they seem to be quite new and the dizzy cap from coil one has suppression written all over it.
Was there a suppressor fitted inside the dizzy on these cars?

One across the ignition coil maybe?

This car never had a radio fitted originally so maybe it doesn't have such nice things?

Advice gratefully received.

Only when I take the foot off the power does the crackle stop. Its not in time with the speed its just constant when under power.

Thanks

[johnwp5bcoupe]

Nov 17, 2017 10:16:33 GMT stan said:

Aaagh ! Depression not suppression.

So i fitted the capacitor to the dynamo last night no difference.

I checked the ignition leads they seem to be quite new and the dizzy cap from coil one has suppression written all over it.
Was there a suppressor fitted inside the dizzy on these cars?

One across the ignition coil maybe?

This car never had a radio fitted originally so maybe it doesn't have such nice things?

Advice gratefully received.

Only when I take the foot off the power does the crackle stop. Its not in time with the speed its just constant when under power.

Thanks

Hi Stan I thought we talking about a whine not a crackle that's a different can of worms!! are the plug leads copper or carbon?

[stan]

Nov 17, 2017 12:27:08 GMT johnwp5bcoupe said:

Nov 17, 2017 10:16:33 GMT stan said:

Aaagh ! Depression not suppression.

So i fitted the capacitor to the dynamo last night no difference.

I checked the ignition leads they seem to be quite new and the dizzy cap from coil one has suppression written all over it.
Was there a suppressor fitted inside the dizzy on these cars?

One across the ignition coil maybe?

This car never had a radio fitted originally so maybe it doesn't have such nice things?

Advice gratefully received.

Only when I take the foot off the power does the crackle stop. Its not in time with the speed its just constant when under power.

Thanks

Hi Stan I thought we talking about a whine not a crackle that's a different can of worms!! are the plug leads copper or carbon?

[stan]

Nov 17, 2017 12:27:08 GMT johnwp5bcoupe said:

Nov 17, 2017 10:16:33 GMT stan said:

Aaagh ! Depression not suppression.

So i fitted the capacitor to the dynamo last night no difference.

I checked the ignition leads they seem to be quite new and the dizzy cap from coil one has suppression written all over it.
Was there a suppressor fitted inside the dizzy on these cars?

One across the ignition coil maybe?

This car never had a radio fitted originally so maybe it doesn't have such nice things?

Advice gratefully received.

Only when I take the foot off the power does the crackle stop. Its not in time with the speed its just constant when under power.

Thanks

Hi Stan I thought we talking about a whine not a crackle that's a different can of worms!! are the plug leads copper or carbon?

John the only whining is probably me! Haha. Right I went outside and checked the only lead that looks to be non copper is the one with suppression written on it to one of the plugs not he coil as I originally thought. So is it a case of ditching the copper for carbon ones?

Is this a jr Wadhams special? I just ordered some parts from them cant face the postage cost a second time just for leads? 😂🤔

[johnwp5bcoupe]

Stan Copper is ok if you have suppression caps on the plugs?

[stan]

Nov 17, 2017 17:49:10 GMT johnwp5bcoupe said:

Stan Copper is ok if you have suppression caps on the plugs?

Well the caps look like they are from 20 year old plastic bottle tops! New leads but too tight to buy new caps, something I find a lot with old cars. Shiny new ferrari on crossply remould tyres because they were cheap.😂😂

I will buy some uncut silicone leads and do them a proper length , these look a little short in places. (I am the person to buy cars from,I tend to be a little anal about stuff like this, things have to be right and should work as expected. )😀

[djm16]

Stan, what is a "new isolated negative earth radio"?

The correct way to do this to avoid earthing difficulties, and the problem of having a radio whose chassis is live, is to have a common ground - car chassis connected to the radio chassis ground. Then you supply power to the radio via a 10A isolated DC-DC converter. These are not cheap.

re interference, there are numerous sources:

1) MW / VHF radio wave leakage from the un-suppressed plugs leads. This is fairly easy to identify with a portable radio. Does it get worse when you open the hood and hold the aerial near the plug leads.

2) Low frequency 2khz - 10 kHz pulses on the common power connection occurring each time the coil draws current to recharge. Fix is to bridge the coil power supply with a 0.2 (or higher) uF paper capacitor (same as condensor in the distributor).

3) Medium frequency whine from an un-suppressed generator. It is supposed to have a suppression capacitor between the D terminal and ground.

4) Can be overlooked, but constant arcing at the voltage control contacts in the voltage control box. Not much you can do to suppress this, but cleaning the contacts can make a surprising difference.

5) LED headlight drivers create a similar problem to the ignition coil. They consist of a switching power supply with frequency in the 20kHz range that not unusually creates a radio frequency interference signal on the common power supply. It is also to an extent engine speed dependent.

Lastly, only when you have addressed all the above and still have a residual interference, then you can fit an in-line power supply conditioner for the radio.

[Warwick]

Stan,
Have you tried tuning in to a different radio station? Sometimes the whining comes from the presenters.

[Colin McA]

Is the radio ok when the engine isnt running and just the radio switched on?

Where are you taking the power feeds from? I would try powering it directly from the battery and see how that goes.

The other thing I would try is put some load on the electrics, put the headlamps and blower on and see if it is the same. You may be generating too much electricity. If that is the case I would consider fitting a zener diode to regulate the radio voltage.

Colin

[stan]

Nov 17, 2017 23:43:49 GMT djm16 said:

Stan, what is a "new isolated negative earth radio"?

The correct way to do this to avoid earthing difficulties, and the problem of having a radio whose chassis is live, is to have a common ground - car chassis connected to the radio chassis ground. Then you supply power to the radio via a 10A isolated DC-DC converter. These are not cheap.

re interference, there are numerous sources:

1) MW / VHF radio wave leakage from the un-suppressed plugs leads. This is fairly easy to identify with a portable radio. Does it get worse when you open the hood and hold the aerial near the plug leads.

2) Low frequency 2khz - 10 kHz pulses on the common power connection occurring each time the coil draws current to recharge. Fix is to bridge the coil power supply with a 0.2 (or higher) uF paper capacitor (same as condensor in the distributor).

3) Medium frequency whine from an un-suppressed generator. It is supposed to have a suppression capacitor between the D terminal and ground.

4) Can be overlooked, but constant arcing at the voltage control contacts in the voltage control box. Not much you can do to suppress this, but cleaning the contacts can make a surprising difference.

5) LED headlight drivers create a similar problem to the ignition coil. They consist of a switching power supply with frequency in the 20kHz range that not unusually creates a radio frequency interference signal on the common power supply. It is also to an extent engine speed dependent.

Lastly, only when you have addressed all the above and still have a residual interference, then you can fit an in-line power supply conditioner for the radio.

Thank you for that comprehensive advice its very kind of you. I used to know all this stuff once (used to fix valve radios as a kid for fun!) Forgotten it all now.

The radio is a modern unit, negative earth. I have it fitted in the centre glove box that would have originally had a radio /speaker in there. The radio chassis is isolated physically from the car bodywork ( being a positive earth car) plus I have switched the aerial leads round as the earth on the aerial is positive earth.

I fitted a suppression capacitor to the dynamo but no change.

I have ordered suppressed silicone leads but do I also need suppressed caps or just plain rubber ones?

The radio has Bluetooth also and when I play my music via my phone using Bluetooth it also experiences the same interference.

When the engine is off there is no interference.

Good idea about using a portable radio to track interference under the bonnet. Thanks.

Not had a chance to check the voltage reg yet only had the car a week and its been pressed into service already for work.

The noise is not really speed dependant just when I accelerate the noise starts (crackling noise), when foot off the gas but still driving, it goes quiet again.

The radio is actually fed directly from the battery and has an inline fuse and noise suppression filter wired in.

Thank you for the background info and suggestions I will see how it goes during the next week.

[stan]

Nov 18, 2017 0:48:23 GMT Warwick said:

Stan,
Have you tried tuning in to a different radio station? Sometimes the whining comes from the presenters.

I know exactly what you mean haha!

[stan]

Nov 18, 2017 9:03:23 GMT Colin McA said:

Is the radio ok when the engine isnt running and just the radio switched on?

Where are you taking the power feeds from? I would try powering it directly from the battery and see how that goes.

The other thing I would try is put some load on the electrics, put the headlamps and blower on and see if it is the same. You may be generating too much electricity. If that is the case I would consider fitting a zener diode to regulate the radio voltage.

Colin

Thanks Colin.

The radio is fine when engine is off no intereference.

The power leads run directly from the battery via an inline fuse/noise supression filter.

When I switch on all or any electrics it makes no difference. There is no additional interference from the wipers or fan. It has to be the ignition leads/ dizzy maybe?

Looking at the leads they are copper and although look new do look a bit cheap so maybe they are not the best quality?

I have ordered some suppressed silicone ones but do I also need suppressed caps too?

I see NGK seem to have this side of the market covered but I refuse to pay a fortune for a right angled connector just because it has Lucas or some other famous brand imprinted on the top? Its still made for peanuts in China. All green boxed Lucas is made in China anyway now ironically its probably better quality than some of the original stuff, Joe Lucas really is the Prince of Darkness! 😁😁😁

[johnwp5bcoupe]

You wont need suppression caps with Carbon leads Stan you can suppress the Distributor with a Capacitor! Keep at it

I don't know if your floating radio chassis is contributing to your problem?

[stan]

Nov 21, 2017 10:01:22 GMT johnwp5bcoupe said:

You wont need suppression caps with Carbon leads Stan you can suppress the Distributor with a Capacitor! Keep at it

I don't know if your floating radio chassis is contributing to your problem?

Thanks who knows maybe I have discovered a new world power source! 😂

I will try to get them fitted tonight.

All my work is done late at night under torch light it seems.
Remind me why I purchased this car again oh yes because I always liked the way they looked and love the heady smell of leather, old plastic, hot oil and goodness knows what else I have not found in there yet?

[djm16]

Have you double checked that the radio chassis has no DC connection continuity with the -ve power lead? If it does then there is a risk of shorting the car chassis to the radio chassis.

Re the aerial.
You need continuity between the aerial cable shield, the car chassis and the radio chassis. But this does not need to be DC. So you should disconnect the aerial cable shield near the aerial socket on the radio, and remake continuity with a capacitor. 1 nF ceramic / polyester should be plenty.

Your description of the interference sounds very much like arcing across the voltage control contact in the regulator. If you remove the regulator cover, run the engine at the speed at which the interference develops, and then briefly force the regulator contacts open, you should hear the noise disappear.

You do have a difficulty though. The interference signal is occurring in the -ve power rail, which your strangely wired radio is relying on as a ground reference!

One last thing, try powering the radio from a completely independent power supply, and unplug the aerial from the back of the radio and see if the interference goes away.

[stan]

Nov 21, 2017 23:55:05 GMT djm16 said:

Have you double checked that the radio chassis has no DC connection continuity with the -ve power lead? If it does then there is a risk of shorting the car chassis to the radio chassis.

Re the aerial.
You need continuity between the aerial cable shield, the car chassis and the radio chassis. But this does not need to be DC. So you should disconnect the aerial cable shield near the aerial socket on the radio, and remake continuity with a capacitor. 1 nF ceramic / polyester should be plenty.

Your description of the interference sounds very much like arcing across the voltage control contact in the regulator. If you remove the regulator cover, run the engine at the speed at which the interference develops, and then briefly force the regulator contacts open, you should hear the noise disappear.

You do have a difficulty though. The interference signal is occurring in the -ve power rail, which your strangely wired radio is relying on as a ground reference!

One last thing, try powering the radio from a completely independent power supply, and unplug the aerial from the back of the radio and see if the interference goes away.

Thanks will give that lot a try tonight (all being well) appreciate your advice on this one.

[johnwp5bcoupe]

Nov 22, 2017 15:02:24 GMT stan said:

Nov 21, 2017 23:55:05 GMT djm16 said:

Have you double checked that the radio chassis has no DC connection continuity with the -ve power lead? If it does then there is a risk of shorting the car chassis to the radio chassis.

Re the aerial.
You need continuity between the aerial cable shield, the car chassis and the radio chassis. But this does not need to be DC. So you should disconnect the aerial cable shield near the aerial socket on the radio, and remake continuity with a capacitor. 1 nF ceramic / polyester should be plenty.

Your description of the interference sounds very much like arcing across the voltage control contact in the regulator. If you remove the regulator cover, run the engine at the speed at which the interference develops, and then briefly force the regulator contacts open, you should hear the noise disappear.

You do have a difficulty though. The interference signal is occurring in the -ve power rail, which your strangely wired radio is relying on as a ground reference!

One last thing, try powering the radio from a completely independent power supply, and unplug the aerial from the back of the radio and see if the interference goes away.

Thanks will give that lot a try tonight (all being well) appreciate your advice on this one.

As it's a -VE chassis it will have a connection to the -VE I would have thought? Years ago there was a floating earth radio I am bu**ered if I can remember the make? there was also a Philips with switchable polarity back then as well!
I hope you get it sorted Stan