[Elecraft] Computer RFI in K2

[J. Wolf]

   Recently, I made up the cable to connect my K2/100 to both the KAT100 ATU and my laptop. Everything works just fine...except for RFI from the computer to the radio when any of several logging programs is loaded (N1MM and CommCat being my two main programs). It sounds like a rapidly cycling change in the radio's noise level, and the S-meter reflects this, going from a baseline band noise level up to S9 with a period of just under a second. I've tried ferrite beads on everything, better grounding of the radio, and just connecting to the computer without the ATU, but nothing seems to have worked. The RFI isn't getting in via the coax feedline, since disconnecting it has no effect. In desperation, I tried a different laptop but got the same problem. The connection is via a serial to USB converter, and I've tried two different ones with no resolution of the problem. There's NO problem when the computer is running without either of the logging programs booted, so I'm guessing this might have something to do with polling. Does anyone have any experience with this and, if so, any suggestions?
Jeff, K6JW