[TenTec] PSK31 and an Omni-6+

Peter A. Klein pklein@2alpha.net
Sat, 10 Apr 1999 00:26:25 -0700

Eric, W3DQ says:

>Has anyone tried an Omni-6+ and PSK31?

>I'd be interested to know the resistor values used to interface the radio
>with a SB16 card.  I assume one would use the audio in/mic in connections
on >the back of the radio.

Yes, use the connectors on the back of the radio.

I'm using the Omni Six/Option 1 with both PSK31 and RITTY by K6STI.  I have
been getting away with not using any resistors at all, but have to turn the
Windows Volume Control virtual "pots" one "click" above minimum.  Set this
way, I get the 1/2 power difference between carrier and idle that's
recommended in the help file.  I'll probably add resistors soon to get a
little more control out of the mike gain pot--right now it's set only a few
degrees off of zero.  However, others have pronounced my signal clean.

When I used an Icom 751a with RITTY, I had 10K in series with the mic lead,
and 330 ohms across.  I'll try similar values on my home-made Omni cable
when I get around to it.  

I suspect the values are not terribly critical.  I've heard people using
everything from 100K to 10K in series (I've heard 27K several times), and
100 ohms to 1 K across.  As long as it doesn't overdrive, or force you to
crank your mic gain so high that you get crud in the signal, it's fine.
The mic gain has a pretty wide range.  I suggest using whatever you've got
in your junk box, just twist the leads together and try.  Aim for a value
that puts your mic gain about where you use it for your mic--probably 9 to
12 o'clock.

I do need an isolation transformer between the sound card output and the
Omni's audio in jack, or I get hum/feedback.  Keep mic signal ground
separate from chassis ground.  I switch between the sound card and a HAL
P38, and I've got two Radio Shack switch boxes, one for the (Omni's) mic
lead, and the other for receive audio on the left channel and PTT on the
right channel.

The fixed audio out jack on the back of the Omni has less output power than
many other transceivers.  I've found that I have to use the Mic Input of
the sound card rather than the Line Input, despite dire warnings to the
contrary in the RITTY and PSK manuals.

One nice thing about the Omni (at least with the hand mic) is that the PTT
switch leaves it out of the circuit when not pressed, so you don't have to
disconnect the microphone.  (Or did I wire it that way?  Can't remember now).

Hope this helps!  73 from KD7MW,

--- Peter
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