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Author Topic: RF getting into HEI Ignition? Maybe?  (Read 392 times)
AL2F
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Posts: 7




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« on: April 08, 2005, 07:08:51 PM »

I have a 1975 3/4ton Chevy with a 350 cu.in., motor with HEI ignition.  I have had to replace the ignition control module 3 times since I started working mobile in the truck, that’s only about 2 years.  I have observed that on 17 and 15 meters my tachometer moves when I am talking, so some current is being picked up in the distributor or just the tach wire.  Could this stray rf be cooking the control module?  I've been told that these modules are known to be trouble.  I'm trying to figure out if it's an RF problem or some other defect in my ignition system.

Radio/Antenna setup….FT-857d into a KJ7U screwdriver antenna on the front bumper.  Usually running 95w on HF.  I don't have any trouble with Ignition getting into the radio.  The only noises getting into the radio are the wiper motor and the heater fan motor.

Has anyone else run into this before?  Any ideas would be great.

Thanks for the Help.

AL2F
Kris in Whittier AK
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K0BG
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Posts: 9868


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« Reply #1 on: April 09, 2005, 05:40:44 AM »

The HEI is in the same vain as Ford's Thick-Film-Ignition system. It's old technology and not very reliable. In my opinion it is not the RF that is causing your problem.

As for the tach, a split bead of two in the right place should cure it.

One of the most often asked questions in the mobile forum goes something like this; Will I cook my (insert what ever electronic automobile device you can think of here)? The fact is, most automotive electronics are robust and well protected from stray RF, especially air bag controls. Notice I said most. The device(s) most problematic is car stereos and power amplifiers. No matter what name appears on them, they are basically junk when it comes to RFI suppression. In fact, a lot of the high end stuff is worse than factory stock.

Alan, KØBG
www.k0bg.com
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AL2F
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Posts: 7




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« Reply #2 on: April 09, 2005, 10:14:23 AM »

Alan,
Thanks for the quick response.  That's what I was hoping.   Not to happy about the crappy ignition system, but I bought an extra control module just in case.  Now I can go back to HF mobiling around.

73-al2f
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KL7IPV
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Posts: 984




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« Reply #3 on: April 19, 2005, 10:20:47 PM »

I had a similar problem in my 89 Chev PU. The Hustler was mounted on the front bumber and whenever I transmitted on HF, it turned the cruise control off. Shielding the hood using braid helped but it never did go away unless I ran at about 50 watts. Good luck.

Frank
KL7IPV
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NE2I
Member

Posts: 12




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« Reply #4 on: April 28, 2005, 04:29:45 PM »

I always dumped the HEI distributors quickly.
Get yourself a MSD disrtibutor and MSD 6 control box
solves 99 percent of all your ignition problems and even
gets you a little power and fuel economy.
summitracing has all the stuff you need.....

George
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