[Elecraft] K3: Noise from computer gets into K3 via RS232 cable

[LY2IJ]

Hi,
I run on 160 in wwssb and faced strange strong wide noise on any antenna
port including with no antenna connected. Problem was solved by
disconnecting RS232 computer cable from radio. It just took too long – I
located it just 5 hours before contest ended. Simle transistor PTT
interface from same com port caused no problems.

Noise is S5..S7, drops down S unit or two when preamp is of, about 5 kHz
wide, little „data“ modulated, sound little like SSB splatters,
located on around 1850, 1875, 1905 then floats down to 1845, 1870 and
further in few minutes, then disappear and reappier again.

Computer here is 9 years old IBM 390X laptop – I need to change it, but
lost the trust in any computers now.
Any ideas hove to get rid of computer generated noise? Filters on cable??
No other computer do that, just mine?

I just hope I didn’t loose to much in contest..

73 Arunas / LY2IJ