[Elecraft] K2 headphone audio for sound card PSK31?

[Jack Smith]

Cathy:

A trick I've used in the past with RTTY demods is to drive the demod 
audio input (or sound card) via a step-up audio transformer.

In the days of tube-type demods, I would connect a tube-type audio 
output transformer backwards across the receiver speaker output, but 
that would produce too much voltage for a sound card. However, a 
transistor audio output transformer should be about right, something in 
the 8 ohm : 200 ohm range.

Of course, you could do the same type of voltage amplification with an 
op amp, but a transformer works well for this application.

Or, you could use the microphone audio input instead of the line input. 
Plenty more gain there, and most computers have an auxiliary +20 dB gain 
switch.

Jack K8ZOA

Cathy James wrote:
>
> I ran some tests this evening with my K2 and my computer sound card 
> and HamScope software.  80 meters was not great, but it was open and 
> there were a number of QSOs going on.
>
> The K2 was able to pick up signals and decode them quite well, and the 
> narrow filters really help block QRM.  (My RTTY filter bandpasses are 
> all over the place, though; I don't think I ever finished setting them 
> up after getting Spectrogram going.  Have to revisit that!)
>
> However, the audio drive from the K2 is much less than from the 
> DX-70TH that I use as my primary digital mode rig.  Although the 
> signals decoded well, the traces on the waterfall barely showed even 
> at fairly high soundcard record volume settings.  With the DX-70TH 
> plugged into the sound card instead, the same signals were brilliant 
> yellow and easily found by eye.
>
> What can I do to increase the audio output level of the K2 for sound 
> card purposes?
>
> Cathy
> N5WVR
>
> _______________________________________________
> Elecraft mailing list
> Post to: Elecraft at mailman.qth.net
> 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
>
>