OEMs have gone back and forth over the years with the "one true ground"
vs completely distributed grounding via the chassis. They seem to
currently be in the phase of using distributed localized grounding
points (with several ground return wires per location), a kind of hybrid
grounding system, if you prefer.
I've always run a pair of wires back to the battery, but with one
important difference. I tie the ground side of the pair near the
battery end to the chassis terminal that the battery uses to 'ground'
the negative to the vehicle chassis. This way, if the battery negative
opens (either because of a loose terminal clamp or a defective
battery-to-chassis connection), you won't get a load dump of the entire
vehicle's current through your radio's ground wire, radio chassis, and
antenna coax shield to wherever you've mounted your antenna.
No OEM will ever recommend connecting the negative return of any
accessory to the battery negative terminal, because of this. Folks that
do this risk a 'thermal event' involving their gear if a load dump
occurs.
Finally, if your DC power cable came with a fuse in the negative lead,
bypass it/take it out! Otherwise, you can blow the fuse in the
negative, and put all your transmitter power load (30A peak for a
typical 100W HF rig) down your antenna coax shield to (again) where ever
you mounted your antenna.
Also, put an inline fuse near the battery end in the plus DC lead, to
guard against any shorts to chassis in the run to the rig. Most
aftermarket installations don't do much to protect the added wiring, and
it could chafe and get cut into someplace. Better to blow the fuse at
the battery end, than to have another 'thermal event' burning up the
wire.
Hope this helps.
73,
-- Dave, N8SBE
> Proper bonding in a vehicle is different from bonding in a fixed
> station. In general, rigs should NOT be bonded to the vehicle chassis,
> and contrary to what is written on the site of a so-called mobile
> authority, DC power should be a pair run directly from the battery,
> ideally a twisted pair. Fundamental reason is that bonding the rig to
> the chassis provides a loop return path for noise and coupling RFI
> to/from the vehicle's computers. Also, the rig is not the source of RF,
> it's the antenna!
> 73, Jim K9YC
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