[Elecraft] DX Doubler/K3 issue

[David Cutter]

Tom

You mention bonding in vehicles and this rang a large bell with me:  all 
military vehicles, land sea and air, require a separate dc return other than 
the chassis for the battery negative terminal.  Filter caps for emc are 
returned to the chassis of the equipment which is strongly bonded to the 
chassis of the vehicle and dc return is a separate wire to the battery 
supply negative.  Transmitter/receiver coax terminals make it tricky.

David
G3UNA

The best fix for this
> problem is to not have common chassis grounds on low voltage
> sensitive signal leads, a good design isolates the sensitive
> signal leads with isolation transformers. This problem is a
> whole lot like the problem we create in vehicles when we run
> the negative radio lead to the battery negative post. People
> designing gear have to learn to not create a harmful path. I
> can't imagine having an audio interface device that connects
> audio and signal lead grounds all together at low
> frequencies or dc!
>
> The voltage induced this way is typically hundreds of times
> higher in magnitude than voltage induced by flux leakage
> from power transformers. Worse yet, it is an extremely low
> impedance source making it very difficult to "bypass".
>
> 73 Tom
>
>