[Elecraft] Kio2 cablength

[Jim Brown]

On Mon, 4 Jul 2005 21:18:34 -0400, kf4yox at earthlink.net wrote:

>Hi I was wondering if there would be a problem using a 25 foot length of
>cable from my K2 to the computer.

If you're going to run a longer cable, I STRONGLY recommend using twisted 
pair for the connection between the computer and the K2. The best solution 
is shielded CAT5; the second best solution is unshielded CAT5, or two runs 
of braid-shielded twisted pair. This will do two things. First, the 
twisted pairs will reduce the susceptibility of both the K2 and the 
computer to "RF in the shack" problems. Second, CAT5 cable has very low 
capacitance, which allows RS232 to work for longer distances. 

To gain the benefits of the twisting, use one pair (orange and 
orange/white, for example) to connect pin 2, with orange to pin 2 and 
orange/white to pin 5. Likewise, green to pin 3, green/white to pin 5. The 
overall shield should go to the DB9 shell on each end, not to pin 5.

If you are using UN-shielded twisted pair, connect the return of each pair 
to the DB9 shell, NOT to pin 5. This puts a "band-aid" on pin 1 problems 
on each end. 

These techniques solved a nasty RFI problem for me that was causing my 
computer to grind to a halt at about 10 watts out to a long wire antenna 
that ended in the shack and ran right past the RS232 cable. Now I can run 
the K2/100 with my Titan amp at full power with no RFI problems. 

For more about pin 1 problems, see my website.  

http://audiosystemsgroup.com/publish

73,

Jim Brown K9YC