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

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[MontyS]

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
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com 

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com