[Elecraft] [K2] length of control cables between K2 and KAT100/KPA100

[John Shadle]

I'm almost done with the construction of my K2 "twins" (K2,
KAT100/KPA100) and am about to construct the control cable for the K2
--> KAT100/KPA100 --> PC.

The instructions from the KIO2 state that the length of the cable can
be up to 15' (the total length included in the kit), but the KAT100
manual states that it should be 2' (between the K2 and the KAT100).
The KAT100 instructions also state that "A longer cable can also be
used, but it will have to be tested to ensure that is is not subject
to RF interference". Other conflicting information comes from the KIO2
manual (first page) which states that "RS-232 interfaces are often
significant sources of RFI" but that "the KIO2's serial interface
provides an HF crystal oscillator (operating well outside of any ham
band) to generate the negative driver voltage."

So, which is it? ;-)

I understand that the cable can pick up stray RF (I'm guessing that's
why the KAT100 instructions state to make the cable as short as
needed). Are the cables sufficiently shielded, or not? Should I
consider purchasing other 4 conductor cables to replace the ones in
these kits?

As I sidenote, if anyone has information about using USB to serial
converters for K2 rig control, please reply with that as well. I'm
about to go searching through the archives now on that subject...

Thanks
-john W4PAH