[Elecraft] T32MI K3 rig problem

[Tom W8JI]

> OK on seeing the problem of the K3 shutting down when the 
> transmitter is keyed
> on 40 Meters. If there is a 40 Meter 'sensitivity-to-RF' 
> problem with the K3,
> then there is a reason for it. It may take a super sleuth 
> to discover the cause.
> It may be a component resonance problem within the radio 
> such as a combination
> of a trace length and a bypass cap causing a parallel 
> resonant circuit at 40M.
> Who knows.

The RF should never be making it back inside the cabinet. 
All the super sleuth really has to do is look at external 
ports and find the bad bypassing, poor grounding of a 
shield, or ground loop. That shouldn't take much time, if it 
is a radio problem.

> If the problem is being triggered by 40 Meter RF and the 
> internal fix can not be
> found, then the user should be able to take some actions 
> to reduce the problem.
> Stray RF can be reduced with a good RF ground at the 
> radio, using a resonant
> antenna with low standing waves, adding coax chokes or 
> installing ferrites on
> antenna coax feedline. Your mileage may vary :-).

Although SWR can indirectly affect common mode current by 
changing voltages and currents at the antenna feedpoint, SWR 
by itself is unrelated to common mode RFI, as is resonance 
of the antenna. Common mode is caused by an improper feed 
system (bad antenna or feedline construction or design) or 
an antenna too close to the shack, and that can happen with 
equal severity if SWR is 1:1 or 100:1.

The first thing to look at is the antenna system and what 
goes on around the feedpoint and feedline. The second thing 
is something wrong with I/O port design.

http://www.w8ji.com/rfi_rf_grounding.htm

73 Tom