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

[Monty Shultes]

Hello Arunas -

I had this problem.   The interference was worst on 160.

Are you using a rig-control or logging program like HRD deluxe?  These 
programs poll the PC and can create the interfering hash you are hearing. 
It was made worse by an unshielded USB-to-serial adapter.  The interference 
disappeared when I put a serial port in the computer and used a good 
shielded serial cable.

I had limited success with toroids on the USB-to-serial cable.  I believe 
you will find references in the email archive as to how to use toroids. 
Using a shielded cable is important.

Monty K2DLJ

> 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
>
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