[Elecraft] Mobile from 117 VAC

[Jim Brown]

It IS critical that all conductive parts of the vehicle be bonded 
together. It is critical for two reasons. First, because those parts 
carry antenna current on both TX and RX, and to be effective as a 
counterpoise, they must have good electrical contact. You're absolutely 
right about paint. It's a HUGE issue.

Second, good EMC design calls for cables supporting signals for 
sensitive circuits to be run in close proximity to a "ground" plane. 
Noise current is coupled far better to the much larger ground plane than 
to the cables. But this falls apart if there is a break in the "ground" 
plane, greatly increasing coupling to/from those cables. This mechanism 
is a likely cause (or contributing cause) to my 20M RF locking up the 
computer in my Toyota.

And, of course, it has long been good practice to bond the tail pipe to 
minimize old fashioned automotive noise. :)

73, Jim K9YC

On 10/9/2017 10:33 AM, Rick WA6NHC wrote:
> My rule:  Bond EVERYTHING to the chassis, including chassis elements 
> to each other (paint is a pretty good insulator).  While that does 
> have a *small* effect on noise (the every wire IS an antenna 
> consideration); mostly bonding is to keep the RF (more correctly RFI) 
> out of systems where it doesn't belong , including induction and 
> radiation along the power cabling; to radiate from the antenna (while 
> power sources are also another good place to provide some twist in the 
> cable).  More bonding means more energy to the (intended) antenna and 
> higher efficiencies.