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Radio Suppression
#1
Borotosh Avatar
Borotosh Andy C
Christchurch, Dorset, UK   GBR
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1973 MG MGB
I have recently fitted new HT leads and an electronic ignition kit and the interference on my radio has got worse, it used to be okay on FM but poor on MW, now poor on both, any suggestions?

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Re: Radio Suppression
#2
dohc281 Avatar
dohc281 Silver Member Ira Eckstein
Laurel Springs, NJ, USA   USA
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1967 MG MGB
1973 MG Midget MkIII
1998 Ford Mustang
This usually means that the ignition wires are unshielded and that caused the poor radio reception.


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Re: Radio Suppression
#3
ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
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1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
1995 Toyota Highlander "Hi Ace Van"
2022 MG ZS
Hi Andy,

A common problem, in the day.

Your new HT leads, what sort are they? If they are solid wire then that is one cause of interference. They need to be resistive, Bosch make good ones, and there are others, that I've not had any experience with, such as NGK. Maybe someone else can recommend others. Your ignition system is unballasted and you have a voltage sensing tachometer, so you can fit a suppression capacitor from the positive terminal of the coil to ground. Should be available from any parts store. Make sure that the radio has a good earth, it's usually through the case, so mounting is important. Also make sure that the antenna is properly earthed, where it mounts.

Herb .


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Edited 1 time(s). Last edit at 2024-04-16 03:20 PM by ozieagle.

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Re: Radio Suppression
#4
Borotosh Avatar
Borotosh Andy C
Christchurch, Dorset, UK   GBR
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1973 MG MGB
Hi Herb

Looking back at my order it just says MGB performance Silicone, fitting a capacitor to the coil sounds like an easy option, I will give it a go.

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Re: Radio Suppression
#5
Borotosh Avatar
Borotosh Andy C
Christchurch, Dorset, UK   GBR
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1973 MG MGB
I obviously went to Halfords to get a suppressor, no chance.
I have tried MGOC website and Rimmer Bros, no luck
Googled with no luck
Anybody in the UK know where I can purchase?
Thanks
Andy

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Re: Radio Suppression
#6
ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
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1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
1995 Toyota Highlander "Hi Ace Van"
2022 MG ZS
Hi,

You could try a points distributor capacitor.

Herb


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Attachments:
Capacitor.jpg    29.3 KB
Capacitor.jpg

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Re: Radio Suppression
#7
Borotosh Avatar
Borotosh Andy C
Christchurch, Dorset, UK   GBR
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1973 MG MGB
Thanks for the tip Herb

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Re: Radio Suppression
#8
John37 Avatar
John37 John M
Abingdon, Oxfordshire, UK   GBR
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1978 MG MGB GT
In reply to # 4786306 by ozieagle Hi,

You could try a points distributor capacitor.

Herb

It's not big enough.
ISTR the points capacitor is 0.1 microfarad. A suppression capacitor should be 1 microfarad.


John
1978 MGB GT UK spec

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Re: Radio Suppression
#9
rrikola Avatar
rrikola Platinum Member Robert Ikola
Santa Maria, CA, USA   USA
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1966 MG MGB
Spark plug wires have all different resistance. NGK, a popular wire has very little resistance, I think like 500 ohms , other wires have 10's of thousands of ohms resistance. You might want to try measuring your wires with a ohm meter. You may get help by switching your wires to ones with more resistance.



Edited 1 time(s). Last edit at 2024-04-24 10:33 AM by rrikola.

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Re: Radio Suppression
#10
DocDup1 Avatar
DocDup1 Gold Member Richard Watson
Carmel, CA, USA   USA
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1965 Chevrolet Corvette
1967 Chevrolet Corvette
1967 MG MGB GT
1968 Triumph TR4A    & more
I realize that this is from a different world, but I have had this problem on my Corvettes. The Corvette has a fiberglass body which magnifies the problem. On my 67 Corvette, the plug wires have a stainless steel mesh that shields the radio. Reproduction wires that the suppliers sell today are like what you get from Moss today, junk. When you need new wires for a Corvette, you save the old stainless mesh and run new wires inside. Perhaps you could try that with your car. It might be a good test to try shielding your wires with something like aluminum foil. If that works, you could get proper stainless mesh.

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Re: Radio Suppression
#11
Borotosh Avatar
Borotosh Andy C
Christchurch, Dorset, UK   GBR
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1973 MG MGB
Richard, that is interesting, I have a suppressor on order from Rimmer Bros, it doesn’t state it is for MG’s, but reckon it could be okay, if that fails I will try the tin foil tip
Thanks

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Re: Radio Suppression
#12
Borotosh Avatar
Borotosh Andy C
Christchurch, Dorset, UK   GBR
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1973 MG MGB
Well I fitted a suppressor to earth from the positive terminal of my coil and made no difference at all?
FM is not bad, MW is awful

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Re: Radio Suppression
#13
spikemichael Avatar
spikemichael Platinum Member Michael Caputo
Canton, IL, USA   USA
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1973 MG MGB "Freebie"
1973 MG MGB
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Are we talking popping, buzzing, or humming


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'79, '77, '76, '74.5 (rubber dual SU), and '73 owner. Extensive experience in 12v Audio System design and installation. Vendor of Regalia and Promotional Products since 1993. Supplier of Accessories to MOSS. Forum Member since 2009; with a warped sense of humor since birth. Publisher of the annual MGB & GT Calendar, mailed worldwide.


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Re: Radio Suppression
#14
Borotosh Avatar
Borotosh Andy C
Christchurch, Dorset, UK   GBR
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1973 MG MGB
Crackling interference, may have to have another listen to best match your discription

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Re: Radio Suppression
#15
ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
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1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
1995 Toyota Highlander "Hi Ace Van"
2022 MG ZS
Hi Andy,

Have you ensured that the radio's case is well grounded to the car body, as well as the mounting of the antenna? What I do is to sandpaper around the mounting hole to get to bare metal, mount the antenna and then spray the area with some rattle can paint, to reseal the bare metal. Your silicone ign leads should be OK, but worth checking their resistance.

If all of this doesn't solve the problem you need to start thinking about power filters on the power supply to the radio.

Here's and article I found on suppressing interference.

https://www.crutchfield.com/S-4Tus5FfoJ3c/learn/learningcenter/car/noise_suppressors_installation_guide.html

and a photo of a power filter.

Herb


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Attachments:
intereference suppressor.jpg    47.5 KB
intereference suppressor.jpg

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