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[aprssig] 12V wiring ideas

KBØNLY kb0nly at mchsi.com
Sat Oct 29 22:18:19 UTC 2011


If the battery was not the only thing with a faulty ground it would not 
matter as long as the radio is grounded to the body/frame.  That’s the 
misconception that most live by as well.  Also grounding to the battery is 
NOT the best ground for the radio.  Sometimes its actually the worst.  I 
have seen cases where electronics in the vehicle are interfering with the 
radio when connected to the battery, but go to the body/frame at the radio 
install location and those noises go away.  All your doing with a long 
ground wire to the battery is adding an antenna.

73,

Scott KBØNLY


-----Original Message----- 
From: Keith VE7GDH
Sent: Saturday, October 29, 2011 1:16 PM
To: TAPR APRS Mailing List
Subject: Re: [aprssig] 12V wiring ideas

Jim G1HUL wrote...

> Interestingly the advice in the UK about double-fusing and where to
> connect the ground has changed. Used to be both to the battery and
> double-fused. The advice now in the radio industry is to put the
> ground to chassis very close to the battery, and no fuse.

The best connection for the radio is straight to the battery, but the
negative lead should definitely be fused if done this way. If the battery
to ground connection goes open or develops any appreciable resistance,
the radio could end up providing the negative connection to the battery
e.g. from the headlights or even worse, the starting motor. It isn't just
the negative lead to the radio that you are trying to protect. It is also
ground traces on the circuit board and other circuitry in the radio
and even the coax shield.

I can sorta see the argument for not fusing the negative lead if you
connect the cable to the chassis instead of to the battery, but what
if the battery was not the only thing with a faulty ground? I think I
would err on the side of caution and fuse the negative lead anyway.

73 es cul - Keith VE7GDH
--
"I may be lost, but I know exactly where I am!"

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