[R-390] Computer RFI and R390s

[Drew Papanek]

Richard,

Very good point regarding use of audio transformer for isolation.  Telephone 
line coupling transformers salvaged from computer modems work well for this 
and audio work.  I recently tested one flat within 3 dB over  30Hz - 40KHz 
with 600 ohm source and load (has 1:1 turns ratio and electrostatic shield 
between primary and secondary).

You can accomplish the same result by using the Line Output of the R-390x 
(being balanced it is already isolated).

Drew


>From: "Richard Biddle" <theprof@texoma.net>
>Subject: RE:  [R-390] Computer RFI and R390s
>
>If you are connecting the R-390 to the computer audio card, you may also
>want to try a 600ohm/600ohm isolation transformer in the audio line.  I
>had a ground loop problem that cleared right up when I did this.  I also
>put a Topaz line isolation transformer on the primary of the radio
>before the variac.
>
> >How do you guys keep out computer hash from your listening/receiving?
> >Turning the computer off isn't viable, since one of the programs I use
>is a
> >RTTY program.
>
>73 de Richard W5SRB


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