[aprssig] 12V wiring ideas

Jim (List) jim.list at stuckinthemud.org
Sat Oct 29 15:37:24 CDT 2011

Well aware of the reasons for negative fusing, and agree about still doing
it to the battery (avoids rusty joints!).

A difficulty (at least in the UK) could arise if there was an accident that,
for some reason, your fitted kit was deemed to be a contributory cause and
it wasn't done to the "industry standard" (even though it's not a legal
requirement), insurance companies can get nasty about it and not pay out and
could end up in a legal mess.

Mine are always battery connected and dual-fused!


-----Original Message-----
From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
Of Keith VE7GDH
Sent: 29 October 2011 19:17
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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