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Author Topic: RFI in 2500HD - Help!  (Read 420 times)
WR1N
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Posts: 5




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« on: August 05, 2002, 03:56:43 PM »

I have installed a 706MKIIG directly to the battery with 10awg wire.  It is mounted under the rear seat in the extended cab.  The antenna is a Diamond HV7a attached to the cargo box.  

I have attached braided ground straps from the radio to chassis and antenna to main chassis.

SWR is better than 2:1 in operating segments of the 20 and 10 meters.  

The problem is that I am getting audio(RF) in the speaker system of the factory radio with the radio off on 10 and 20 meters at any power greater than 10 watts.

Also I am getting ignition noise but the 706 filter basically is taking care of that for now.

Any input on the RF into the speaker system is greatly appreciated.  Also any steps to improve the ignition noise would be good. (it is not alternater noise)

TIA,

Rob - WR1N
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K0BG
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« Reply #1 on: August 06, 2002, 05:26:44 AM »

You didn't give the brand, but I think a 2500HD is a Dodge. Here is someting to try. Or perhaps this is a question.

Does the RFI appear when the ignition is off? Or on? (Some premium sound packages switch the power amp with the ignition switch, not the one on the radio.) Either way, the best 'cure' without tearing into the radio is a few well placed split ferrite beads. These can be placed over the power leads and/or speaker leads.

Currently, RF Parts are closing out their stock and you can save a few bucks. Palomar Engineers also sells them.

As for the ignition noise. One respondent to a comment I made on this forum stated he had used split beads on his ignition wires to great affect. I've not tried it, but some friend of mine who have also claim it works. You're on you own here, but one work of causion. Most ignition wires nowadays are 8mm and the smaller 1/4" bead won't go over them. The 1/2" seem too loose, but will work just the same. By the way, these ferrite are designed to operate at a maximum of about 1 Mhz, so at higher freqencies, they get very lossy. It's like putting a resistor in the line without cutting into it.

While you are strapping things, make sure the doors, hood, bed and other bolted on things are strapped to chassis also.

One last item. In case you haven't found out already, using the 706's noise blanker will greatly increase the already bad intermode problems it exhibits due to its wide frontend.

Alan, KØBG
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WR1N
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« Reply #2 on: August 06, 2002, 05:36:41 AM »

Thanks for the reply.  The brand is a Chevorlet.

I am going to try a set of Magnicore(sp?) for the ignition noise. I have a set from 99 Vette and I believe they will work on the Vortec engine in the 2500HD as well.  Saw on a previous post that they seemed to help ignition noise.

I remember some other folks mentioning issues with the new model Chevorlet trucks and RFI.  However, it was not in this forum.  I was hoping that someone else has gone through this with a Silverado 1500, 2500HD, Tahoe, or Suburban.

Also, thanks for the heads up on the intermod.  Yes it is truly terrible.  Never thought that the NB could effect it.

Any other input is appreciated.

Rob
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K0BG
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« Reply #3 on: August 06, 2002, 07:53:21 AM »

I looked at my neighbor's 2002 GMC Denali (same engine as yours I think) and it has what appears to be good quality plug wiring. I'm not sure replacing them would help. If you already have the wires, well... it worth a try.

I've been meaning to order a few of the beads RF Parts have with the intent to clip them over my own plug wires. As it stands, I have a little (<S2) noise from the ignition and then only on heavy acceleration (lucky I guess).

The most effective change I made was putting a beads (2) over the fuel injection harness. What was an S4 noise flat went away!

I'm one of these folks who pays cash for cars, and I always insist a set of Service Manuals is included in the deal. It makes running down and fixing RFI problems much easier.

Let me know if the wires help.

Alan, KØBG
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