[hpsdr] ozy/janus as soundcard for digital modes

[Jeremy McDermond]

On Nov 4, 2011, at 4:07 AM, Stephen West-Fisher wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> 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.

You should be able to use the subreceiver which should be frequency agile within the passband.  That should allow you to pick out the signal you want.  Just mute the main receiver to keep the excess noise out of the audio stream.

> 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?

I wouldn't think you'd need any sort of change to the Janus or Ozy firmware.  You get the sample values, you'd just need to change it so that you can massage it into a format that the Windows subsystem is going to like.  Check out the Ozy packet format documentation at http://openhpsdr.org/support/Ozy/USB_protocol_V1.35.pdf.  This tells you what's coming across the USB from Ozy when you're using Janus.  

> 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.

I'm not a Windows guy, and I'm definitely not a kernel guy so I can't necessarily tell you whether it's easy or hard on Windows.  I wouldn't imagine it being significantly harder than a SCSI driver.

> --
> 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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--
Jeremy McDermond (NH6Z)
Xenotropic Systems
mcdermj at xenotropic.com




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