RF Burns from Microphone

[JC_enfield]

:mellow:Im hoping someone can give me some advice on this one..

i have a president lincoln wired in my car. both Linear RM KL200p (100watt) and radio run directly from the battery. on the roof of the car is a Sirio 4000pl

Every time i go to key up the microphone (Astatic Minitueman) i get nasty RF burns off of the metal parts of the microphone. it really hot with or with out linear, of course its worse with the linear but still burns with out it on 5watts.

can anyone point me in the right direction at all? when i use the radio in my house on my homebase powersupply and same microphone and same linear amp i get no RF burns at all.

could this be something to do with grounding of the radio unit? or could it have something to do with the grounding of the Antenna on the roof of the car?

Hope someone can help me!

Cheers
73's
Joe 26 OK 500

 

[undertaker]

That is your grounding my friend!!! Ground the amplifier to the battery ....

 

[TonyV225]

GROUND GROUND GROUND!!! I was just laughing with my wife about this because its happen us in mobile setups for her in 2 cars. One was a 2950 and Texas Star 400 and the other was wit one of her HF rigs (kenwood ts-50) Yes that D1O4 handheld chrome screen burns the lip like a S.O.B. doesnt it!!?? On her Kenwood it was the metal mic hanger on the back of the Kenwood stock hand mic.

In both applications where the problem was I just added grounding straps and cleaned scraped sanded where the grounds were for better connections and a little extra ground reasure just that GROUND!

Ive seen this actually be a real pain in the @$$ to completely solve.I also used a lightning arrester adapter with the ground lug on it with a ground strap or wire ran to a bolt or screw in frame or under the dash to metal to help with grounding these damn magnetmount antennas this may help a great deal with resolving you situation in particular its always helped in mine. Good luck and Im sure after a little extra grounding it will be good to go and that amazing holy $h!+ feeling after burning your lip on the mic will subside

 

[Robb]

I never had such a problem with my mobile and my Wilson 1000 mag mount, Galaxy DX 99V, and Astatic MM2. It just works fantastic - and NO RF burns whatsoever.

Even with my base station radios (OmegaFOrce S45 and my Yaesu FT-8800R) - RF burns are unheard of.

Interesting problem...

 

[psycho]

You have insufficient ground. Ground the amps to the body or frame. Had a similar problem when I was running a Wilson 5000 mag mount. Grounded amp to the frame with some #2 and no more problem. My mic is just a plastic stock mic but when I touched the radio's case while keyed with everything on it zapped my fingertips.

 

[KB1TPX]

I run both red and black wires from the linear directly to the battery in my mobile set-up, the radio runs off the 12V dash outlet (cigarette lighter socket).

 

[mackmobile43]

Broken coax, either the shield and or center conductor, I have had this happen to me and I found that I had a cheaper mini-8x coax and the center conductor had actually burned into right inside the so-239 so you might consider doing a continuity test through your coax.

 

[Splash1]

you could always just ignore the problem an wear heavy chapstick..

 

[JC_enfield]

GROUND GROUND GROUND!!! I was just laughing with my wife about this because its happen us in mobile setups for her in 2 cars. One was a 2950 and Texas Star 400 and the other was wit one of her HF rigs (kenwood ts-50) Yes that D1O4 handheld chrome screen burns the lip like a S.O.B. doesnt it!!?? On her Kenwood it was the metal mic hanger on the back of the Kenwood stock hand mic.

In both applications where the problem was I just added grounding straps and cleaned scraped sanded where the grounds were for better connections and a little extra ground reasure just that GROUND!

Ive seen this actually be a real pain in the @$$ to completely solve.I also used a lightning arrester adapter with the ground lug on it with a ground strap or wire ran to a bolt or screw in frame or under the dash to metal to help with grounding these damn magnetmount antennas this may help a great deal with resolving you situation in particular its always helped in mine. Good luck and Im sure after a little extra grounding it will be good to go and that amazing holy $h!+ feeling after burning your lip on the mic will subside

Tonyv225 - what your saying makes perfect sense to me mate! I'm going to ground my Rig and Linear better and go from there

Thanks for your response

JC 26ok500

 

[Beetle]

Sounds like a bunch of RF is traveling on the outer surface of the coax shield. Try a choke as close to the feedpoint as you can get it.

 

[W5LZ]

I like the 'ChapStick' solution! Never thought of that before. I also think that the already mentioned grounding is the first step. It may not turn out to be that simple, but typically it is.
That 'grounding' to the battery (hate that expression) isn't -the- solution, but grounding to the metal of the vehicle is. That doesn't pertain to supplying power to anything, but does with stray RF stuff, which is your problem.
- 'Doc

(Ah! The smell of burning mustache hair in the morning/afternoon/evening, ain't it just grand?)