[Elecraft] KRC2 /K3

[Jim Brown]

On 9/5/2013 1:09 PM, Pfizenmayer wrote:
> OR -   is it worth changing to the RS232 bus and using the BCD data from  the K3 ?  Looking at the KRC2 schematic , it looks like the microprocessor is still in the act with the RS232 inputs going thru it . But I have filtered  RS232 data lines with   Ferroxcube VK400 2 1/2 turn hi mu ferrite chokes and 0.001's at least on PTT and KEY  lines with no problems.

I inherited a pair of KRC2s from N6RNO as part of the bandpass filter 
kit for our CQP multi-op setup. As built, they are FULL of Pin One 
Problems, and they are completely unshielded (thanks to paint between 
the chassis and things that are intended to contact it, and paint 
between sections of the enclosure that should make contact but do not). 
It took me an hour or two on each unit to clean up the mess.

Most "RF in the shack" is the result of Pin One Problems.  If your 
antennas are close to your shack, they will put RF in your shack, but 
our equipment SHOULD be designed to reject it. Pin One Problems are an 
open door into equipment for hum, buzz, and RFI.

Lots of detailed stuff about Pin One Problems on my website. 
http://k9yc.com/RFI-Ham.pdf and http://k9yc.com/publish.htm

One very useful piece of information is that all that is required to get 
band data from a K3 to a KRC2 is a single run of coax to connect the AUX 
BUS.  Pin One Problems can be avoided by connecting the coax shield at 
both ends to the SHELL of the DB-connectors. BUT -- in the KRC2, the 
shells of the DB-connectors are insulated from the chassis, so that's 
one of the messes that you must clean up.

Both the K3 and KRC2 are designed to be "universal" in their AUX 
interfaces, so they provide BCD data on other pins in the DB15 for use 
with other radios and other interface equipment.

Another idea Hank -- if you're using an RS232 interface, see my notes 
about using CAT5 cable to build your own RS232 cable. Twisted pair 
provides strong rejection of hum, buzz, and  RFI.  Use one pair for each 
signalling circuit, with the solid color going to the high side pins (2, 
3, 4, 7) and the striped conductors twisted together and connected to 
the DB9 shell.

73, Jim K9YC