[Elecraft] K3: Added protection for RS-232 port

[Jim Brown]

On Sun, 18 Jul 2010 20:59:43 -0400, Pete Smith wrote:

>I've been thinking about how one might go about adding some protection 
>for the apparently fragile (and expensive) RS-232 port on the K3.

I strongly suspect this is more pin 1 stuff. Connect the shield, if there 
is one, to the CHASSIS, not the so-called signal common (pin 5 on DB9s). 
I also strongly recommend using CAT5 for serial cables, using one pair 
for each communications circuit, and tying all the signal returns to the 
chassis (via the DB9 shell), NOT pin 5. Most DB9s support that. Details 
on my website, both in the RFI Tutorial (Solving Problems in the Shack), 
and in the Ham Interfacing power point.  

Another point. Study the material on my website about shunt mode and 
serial mode surge suppression. Most lightning-induced failures of 
interconnected equipment is caused by shunt mode surge suppressors 
(MOVs). 

73, Jim Brown K9YC