[aprssig] APRS In A Car

David Huff davidh at cf.distek.com
Tue Jan 24 11:59:03 EST 2006

The other part of this answer is EMI (Electro-Mangnetic Interference).
Most radios do not have heavy duty noise filtering on the power inputs,
so they tell you to go to the cleanest power supply available on your
vehicle, the battery.  The last thing they want to see is you wiring the
power for your radio to the blower motor leads or other noisy
electronics.  That electrical noise will get transferred into your
radio.  There are many tricks people use to eliminate this problem, from
ferrites, filters, and even shielded power cables.

David KC0GFO

Jason KG4WSV wrote on Jan 24 2006

> I'm not disputing what you say, but why does Kenwood tell us (in the 
> D700 manual), to wire directly to the battery both + and -, and to 
> make sure to leave fuse holders in both + and - leads?

Because that's the most reliable power source. What is best for the
"power wise" isn't necessarily what's best for it (or the supply lead)
the connection from the battery to the chassis or frame goes bad... 
especially when you try to start the engine and the negative lead from
radio tries to pass a couple of hundred amps through it. With the
lead fused, it will blow the fuse and protect the wire. Without it, you 
would be looking at a meltdown situation.

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