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

[Jim Brown]

On 10/21/2010 6:36 AM, John Shadle wrote:
> 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."

I don't know what kind of cable is currently shipped with the K2, but 
most shipped with a very poor choice -- parallel wires inside a 
foil/drain shield. I experienced severe RFI that I traced to that cable, 
and experimented with several types of twisted pair cables and noted 
their effects. Parallel wires are WELL known to pick up RF and noise, 
and twisted pair is very well known to reject it.

I evaluated twisted pair cables that were shielded and unshielded. 
Shielding is important ONLY if the rig will be very close to a TX 
antenna running high power above 20 MHz. By high power I mean an amp in 
the 500 watt range or higher. By close, I mean within 5-10 ft.  The 
cable that is likely to pick up RF is the one that runs between the K2 
and the computer.

The details of the serial cable I recommend is in
http://audiosystemsgroup.com/RFI-Ham.pdf   and in
http://audiosystemsgroup.com/HamInterfacing.pdf

73, Jim Brown K9YC