[Elecraft] T32MI K3 rig problem

[Rich - K1HTV]

Tom,
   Your points are well taken. However, my original suggestion was how to
possibly resolve the problem with available resources (wire) that the guys on
rare East Kiribati IOTAs were experiencing when their K3 transmitted on 40
Meters. 

Hopefully the resident Elecraft 'super sleuth' will be able to recreate the
problem and find a fix.

73,
Rich - K1HTV

-----Original Message-----
From: Tom W8JI [mailto:w8ji at w8ji.com] 
Sent: Tuesday, March 30, 2010 9:46 AM
To: Rich - K1HTV; 'Bob Naumann'
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] T32MI K3 rig problem

> 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