[RFI] HF Mobile Installation in 2001 Mazda

[David Jordan]

I agree with Jim...and in Fords that have a variable high voltage
ignition system that radiates and couples to existing factory installed 
loops of single threaded 12+vdc lines, you got one massive RFI problem 
running another single 12vdc line from the ham radio to the battery.

73,
dave
wa3gin

Jim Brown wrote:

> On Fri, 4 Feb 2005 18:19:19 -0500, Tom Rauch wrote:
> 
> 
>>Inside the radio, the negative leads of any HF radio and
>>almost all VHF/UHF amateur radios are virtually always
>>connected together via the chassis or PC board grounds.
> 
> 
> You're thinking resistance, not inductance or loop area. When you 
> get the power via the closely paired cable (even better if it's 
> twisted), you minimize the loop area of any issues with RF on that 
> power connection. If you use only the body of the car for the 
> return, you get a low resistance (and low inductance) for that half 
> of the dc path, but there's a big loop area between the positive 
> lead and the car body, and any trash on the power will then radiate. 
> 
> AND that big loop will act as a receiving antenna, coupling RF onto 
> the power line. That could be a problem if the microprocessors are 
> using the power system to communicate, which I am told some do. 
> 
> Jim Brown  K9YC
> 
> 
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