Hello Eric
I really appreciate your help. So really good ideas. I found lots of
little things and I was told that my audio sounded good. My main frame
of reference was the monitor.
I helped Bruce with he Orion and WL tonight. He really likes the
radio.
73 Paul
> Hi --
>
> I've struggled a bit with this as well. I have learned two
things that might help others:
>
> 1) The widely-quoted Radio Shack isolation transformer may be OK
for RTTY high tones, but not very good for human speech. It has
> poor low frequency and dynamic response, saturates easily, and
introduces a tinny characteristic to the audio. See the 2002 July 17
> posting by W5YR for details.
>
> K3MM has had good luck with Magnetek TY300P 600 ohm hybrid
transformers. Another WriteLog reflector contributor found some less
> expensive solutions from DigiKey, but I can't find his message.
>
> 2) RF on the audio lines can do bad things when it gets into the
audio amplifiers in sound cards. Wrapping lines around ferrite
> chokes sometimes makes a dramatic improvement.
>
> More generally, there are a lot of steps between microphone and
radio transmitter input. People tend to just throw together a
> bunch of cabling and then expect all the levels and impedances to
magically work out and sound good. It's easy to get caught with
> low level ground loops and other extraneous junk on the lines.
>
> I'm contemplating taking a more careful approach, using 600 ohm
balanced lines and providing a more standardized signal level
> (aka 0 dBm) to the transmitter line input/phone patch input jacks
rather than the mic-in jack. That, along with some little boxes
> that provide isolation transformers and RF bypassing (as well as
breaking out stereo soundcard line in/out into mono for SO2R should
> help a lot.
>
> Receive audio is also important. You may not run into this
trouble with a multi-op station, but a SO2R station that's doing a
> lot of headphone switching can also be exposed to this problem.
>
> -- Eric
>
>
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