[hpsdr] ozy/janus as soundcard for digital modes

[Stephen West-Fisher]

What you described is exactly what I am seeing, and why I was confused by
the panadapter display in PowerSDR. Well, that and the fact the PowerSDR
doesn't let you shift the frequency with just Janus/Ozy selected so you
cannot get to the part of the signal being passed by the filters in the
radio. If I tell it there is a Softrock (I have one) and plug in the TS-480
I can get to the radio signal.

So, when you refer to a Windows driver, are you talking about just Windows
code or do you think the Janus firmware would also need work? What
capabilities in addition to those currently in place would you envision?
I've never written a Windows driver but I did do a SCSI driver for SVR4 back
in the dark ages.

--
Stephen West-Fisher
N4IK
-----Original Message-----
From: Phil Harman [mailto:phil at pharman.org] 
Sent: Thursday, November 03, 2011 11:24 PM
To: Stephen West-Fisher
Cc: hpsdr at openhpsdr.org
Subject: Re: [hpsdr] ozy/janus as soundcard for digital modes

Hi Stephen,


> At this point the clue I am looking for is where the problem lies, Janus
> firmware or PowerSDR code?
>

I don't think there is a problem, simply a difference. If you feed the
audio out from your TS480 into a sound card or Janus then you are faced
with the limitations of having a real as apposed to a complex signal.

With a sound card you can feed the digitised signal into various PC
programs to demodulate digital modes etc. Such programs generally expect a
real signal so all is well.

Janus *only* works with PowerSDR and expects a complex input. If you feed
it a real signal then each signal will appear twice on the bandscope and
one will tune in there reverse direction.

If you tune to one of these signals, and feed it to a suitable digital
mode program then it will demodulate correctly. The issue is that all the
signals on the band will create images and some of these *may* fall within
the bandwidth of the signal you are trying to copy.

If you feed in a complex signal, say from a SoftRock, then these images
can be substantially reduced in amplitude.

Janus is a very high performance ADC, up there with the top end sound
cards. But, without a suitable driver, its not, and was not intended to
be, a sound card.

Now... about writing a Windows driver.... :)

73 Phil...VK6APH


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