[Elecraft] Connecting Transceivers in Vehicles - Change

[Paul Christensen]

> K6WLM:

> "For HF mobile installation, GM and others recommend that the radio NOT be 
> grounded in the cabin. Both battery leads should be fused at the battery. 
> The reason for the negitive side fuse is in the event that the battery 
> ground lead to the engine block should go open or have a high resistance 
> there will be very high current trying to find ground when you start the 
> engine. Starter motor current can be in the hundreds of amps. You do NOT 
> want that amount of current flowing thru your rig!"

Fair enough concerning the grounding point, but the negative radio lead 
should be *unfused* and then bond close to the point where the battery bonds 
to the vehicle chassis.   In the case above, it would still be best to 
unfuse the negative radio lead in instances where the radio chassis and 
negative power lead are DC-common.

The danger in your proposal of fusing the negative lead is exactly as stated 
in my last message:  That an opening of the radio's negative fuse line will 
cause the radio's return current to complete through the radio's grounded 
connectors where the chassis of the radio and the negative power leads are 
common.  Now you have an electrical insulation burn issue to deal with in 
your vehicle if the negative fuse blows and the positive radio fuse remains 
intact.  For a 100W-class HF transceiver, that's roughly 20A of current 
during TX in wiring not meant to carry a high DC current load.

Paul, W9AC