[Elecraft] [OT] K9YC's Serial Cable question

[Don Wilhelm]

  Brian,

Jim  may chime in here, but these are my considerations:

Beware of pin 1 - it is ground ONLY only for the K2.  At the computer 
end, the shell is chassis ground (if it exists at all).

You only use 2 of the 4 pairs in the CAT5/6 cable - one for TXD and one 
for RXD.

So for unshielded twisted pair cable, all the returns should connect to 
pin 5 (the RS-232 Signal Ground).

If you are using shielded CAT5/6, connect the pairs the same as for the 
unshielded situation, and then take your choice about the shield - 
connect it to pin 1 only at the K2 end to produce a Faraday shield.
OR (and I would only do this if the computer and K2 are well bonded 
together by separate means), connect the shield to pin 1 at the K2 end 
and to the shell at the computer end.

You could connect the K2 end also to the shell - with the KIO2, the 
shell is connected to ground by a wire to the board, but in the case of 
the KPA100, the only connection of the shell to ground is through the 
mechanical connection offered by the rear panel and the jackscrew sockets.

73,
Don W3FPR


On 6/7/2011 12:06 PM, Brian - N5BCN wrote:
> I read Jim Brown's very informative article on RFI and want to use his method
> to construct a K2/PC control cable using some CAT5 cable I have laying
> around.  Hopefully Jim or someone knowledgeable about this cable can answer
> two questions:
>
> For UNSHIELDED twisted pair CAT5:
> The K2 instructions use Pin 5 for the signal return lines.  Using K9YC's
> method, would I connect the return lines to the DB9 chassis, and then bond
> Pin 5 (or Pin 1, or both) to the chassis also?
>
> For SHIELDED twisted pair:
> The K2 instructions say to connect Pin 1 to the shield on the K2 end, leave
> the shield open on the PC end.  Using K9YC's method, would I connect the
> returns to Pin 5, shield to the DB9 chassis on both ends, and then bond Pin
> 1 and 5 to the DB9 chassis?
>
>