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Author Topic: Ground Mobile Chassis to Car Body Inside Cab ?  (Read 860 times)
KI4IBS
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« on: December 17, 2004, 04:36:28 PM »

   Hi, very new to this, as I just received my call sign a few days ago.

    I mentioned to a local HAM on air that I was repeatedly getting static shocks when I touched my icom-v8000. Not every time, but alot. On his suggestion, I ran a #12 ground from the chassis of the radio to a screw on the body of the car (verified by ohmmeter that it had continuity with the chassis of the car).

    I'm still getting the shocks, though not as many it seems. Mainly after just entering vehicle.

    But, in studying for my General exam, the ARRL book has a short section on mobiles, and  a diagram showing the layout in  a vehicle, and it says "radio chassis NOT grounded to car body" on the picture.

   So which is correct ? Bond it or not ?
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K0BG
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« Reply #1 on: December 18, 2004, 06:10:04 AM »

The build up of static electricity will occur with or without the bonding. Bonding is very important in extending the meager groundplane offered by a vehicle, and to reduce electrical noise of all kinds. If the vehicle has cloth seats (typically nylon), then a solution of a couple of teaspoons of liquid fabric softener and a pint of water sprayed on the seats will cure the problem. You'll have to make a periodic re-spray as the effect falls off after a few days. It only takes a few sprays and it is not necessary to dampen the seats at all. And it smells good too!

Alan, KØBG
www.k0bg.com
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AA4PB
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« Reply #2 on: December 18, 2004, 06:35:07 AM »

The static build up is likely caused by you sliding over the seats. Your body receives the charge and then discharges when you touch the grounded radio. It is grounded whether you have a bonding strap or not, thru the negative power lead and the antenna coax. You should also feel the discharge if you touch any other metal part of the vehicle.

I notice that many gas stations now have a static electricity warning sign regarding this very issue. If you pick up a static charge while sliding out of the seat, it can discharge thru the filler causing a arc right at the filler pipe potentially causing a fire. The warning says to touch the vehicle to discharge any static build up before begining fueling.
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Bob  AA4PB
Garrisonville, VA
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