[WT-support] Win Test sound card dvk ??

[KL7RA]

>The Capacitor should NOT be used with Electret Microphones (like the Heil HC7 element) 
>since these require s DX Bias Voltage for proper operation

None of the eight PC's here put DC on the soundcard mic and the Heil "IC" headsets 
no longer work using the Win-Test DVK option unless I bypass the soundcard by a
relay. 

The Heil HC-4/5 elements do not work for VOX directly connected to the IC-781 
radios but when used with the Win-Test soundcard DVK the Mic elements now have
enough amplification that they work fine. 

The isolation transformer doesn't do anything useful for me but is good engineering 
practice so I installed them.  The RadioShack part number is 273-1374   Audio isolation 
transformer, 1:1 turns ratio. They usually have to order them. $4. I could not find any 
at Dayton last year.

My PC's do not have DC to block but I also installed the blocking caps, RadioShack 
part number 272-1434 1.u tantalum  Plus side towards the soundcard.

RadioShack sells the 1/8" phone jacks for the soundcard, part number 274-286 or you
can just buy them ready made and cut off one end. 

You can build this simple DVK interface box in an evening.

You still should use PTT when using DVK so I have Win-test key my PTT line that is
normally used for CW and I also have a footswitch in parallel for the ops that don't
like/use VOX.

The interface boxes that have a relay to bypass the mic from the soundboard adds 
more parts plus DC input and it is shown in the Win-test Manual as well. I added
yet another toggle switch to use the mic to record instead of unplugging anything.
I also added a dual color LED to indicate where the Mic was going. The box starts
to get crowded as you add "features" like PTT relay, etc. which I did. 

Finally not all soundcards work for DVK regardless of what driver you install. We 
also had the 15 meter position cause RFI to the 20 meter position DVK. I used some 
chokes on the long six foot lines to stop it. I think keeping the audio lines short would
be a good idea if you can.

73 Rich KL7RA