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Author Topic: Interferance on HT and vehicle stereo  (Read 9342 times)
KK4LGR
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Posts: 53




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« on: September 21, 2013, 07:52:31 AM »

Hi all,
I'm a relatively new ham, I've had my technician license for over a year but I've just picked up my first rig within the last month, a Baofeng UV-5R.  I drive a 2003 Chevrolet S10 with the 4.3L V6 engine.  I do not operate the HT on vehicle power, nor do I own a mag mount antenna yet.

When monitoring a QSO, I get a low frequency but high intensity buzzing or popping.  The interference is only present when the engine is turning, and changes pitch and intensity with engine RPM.  I get it on both 2m and 70cm.  I also hear it on the truck's stereo in FM mode, but it's quieter.  It isn't present in CD mode.  On both the handheld and the stereo, the buzz sounds quieter when listening to more powerful, closer stations.  I suspect it's ignition related, so I'm going to closely inspect the ignition wires this evening.

Any hints or tricks to identify the source of the interference would be most appreciated.

73
Adam
KK4LGR
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"Well I'm sure glad we've got these ham radios to talk on."
--Unidentified station heard on 2 meters
K6LCS
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« Reply #1 on: September 21, 2013, 08:37:34 AM »

You already diagnosed your problem - alternator and./or ignition system problems.

You can try resistor spark plugs ... expensive plug cabling ... $600 special alternator ... and still may not eliminate the problem altogether.

It sounds like it is not horribly affecting your signal ... Of course, it is best to get an external antenna and wiring directly to the battery. But you can spend hundreds in time and parts and not get rid of it all.

Reminds me of my 1989 Ford Bronco ... I needed two filterrs on the power line and a really good alternator to make it perfect.

Clint K6LCS
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Clint Bradford, K6LCS
http://www.work-sat.com
KK4LGR
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Posts: 53




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« Reply #2 on: September 21, 2013, 09:29:12 AM »

I may have understated the intensity of the problem.  Most ham transmissions I receive are barely copyable at best under the noise.

The truck just turned 10 years old, It's got 130,000 on it, and I think the spark plug wires are the factory originals.  Would an arcing spark plug wire cause that kind of RF spam?

73,
Adam
KK4LGR
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"Well I'm sure glad we've got these ham radios to talk on."
--Unidentified station heard on 2 meters
GOLDTR8
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« Reply #3 on: September 21, 2013, 02:43:48 PM »

S10 are noisy as you found out.  Do some bonding of exhaust and do a tuneup with new wires.    Also bond hood and bed and things will improve.   This worked for my s10
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G8YMW
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« Reply #4 on: September 21, 2013, 04:13:09 PM »

Is the fuel pump mechanical or electric?
If it is electric, maybe a decoupling cap on the supply line as close to the pump as you can get it?

regards
Tony
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73 de Tony
Sent by WW2 Royal Navy signal lamp
NO2A
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Posts: 843




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« Reply #5 on: September 21, 2013, 04:26:09 PM »

Adam,a popping sound like you describe is by all means an ignition sound. If any spark plug wires are corroded enough or arcing they will cause noise,no question about it. Your stereo could have a bad ground connection too,but that buzzing is ignition noise. Replacing the spark plug wires would help I`m sure. You shouldn`t be hearing that noise on an ht using a battery pack and duck antenna.
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KK4LGR
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« Reply #6 on: September 21, 2013, 05:49:11 PM »

I'm going to replace the spark plug wires.  They need to be changed anyway for the truck's sake, and we'll see if it fixes the spam on the radio.
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"Well I'm sure glad we've got these ham radios to talk on."
--Unidentified station heard on 2 meters
K6LCS
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« Reply #7 on: September 24, 2013, 11:09:27 AM »

See if these folks can help you ...

http://www.classiccreationsnc.com/

That's assuming you're still in the Southern Pines region.

Clint
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Clint Bradford, K6LCS
http://www.work-sat.com
KB4QAA
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« Reply #8 on: September 28, 2013, 10:55:02 AM »

Check out Alan's website on mobiles:  www.k0bg.com
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KK4LGR
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Posts: 53




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« Reply #9 on: September 28, 2013, 04:59:06 PM »

Problem is solved.  It was the distributor.  Replaced the cap and rotor, no more RFI.

Learned about my truck in this exercise; I thought it was modern enough to have a distributorless ignition system, but no.  It's just got a funny looking distributor cap.

Thanks and 73 all,
Adam
KK4LGR
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"Well I'm sure glad we've got these ham radios to talk on."
--Unidentified station heard on 2 meters
WB6DGN
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« Reply #10 on: September 29, 2013, 09:29:18 PM »

Thanks for the question and , especially, for telling us what you found that fixed it.  I just bought an S10, about the same age and with the same engine so your question is especially relevant to me right now.  I, also, would have expected a distributorless ignition system at that age; my '91 Voyager even had it.  Now, I can add a set of ignition parts to the "christening" ritual.
Tom
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