Ross, Tim, Guy and any other fellow sufferers. I use a Firebox as well and reading these posts got me checking around with a hand held scanner and as a result I can confirm that the firewire cable is indeed radiating quite badly. I've found two peaks around 13.968 and 16.357 Mhz and is strongest at the Firebox end reducing slightly as the scanner is moved down the cable towards the pc connection. With the SDR I can hear the broadband noise (bit like a fast moving steam train, chuff-chuff-chuff etc) all the way from 10mhz to 20mhz at around S3 increasing to S7 at the peak frequencies. Its probably still there below 10mhz but is covered up by the normal qrm etc. Did the same check with my TS850 with the same result.
Anyway, I managed to get two turns of the Firewire cable on 3 Fair-Rite type 43 cores (2643802702) and it cured the problem immediately. Type 43 should provide a better performance at HF as opposed to the FT-140-J core which appears to be better suited to 2mhz and below. Trevor G0KTN
