[hpsdr] Sample rate & Audio output

[Jeremy McDermond]

On Mar 27, 2013, at 2:39 PM, john clark <n0ure at yahoo.com> wrote:

I don't see that you got any answer to your questions, John, so I'll see if I can answer what I can even though I'm the "Apple guy."

> In PowerSDR the Audio setting tab, is the Sample rate 48000, 96000, 384000 the sample rate the BW of the audio output? ( Is it Sample rate or Bandwidth?)

That's the sample rate of the hardware.  It's also the bandwidth that's going to come into PowerSDR from the hardware.  PowerSDR will then decimate, filter and demodulate those samples to give you SSB, CW or whatever you've asked it for.  The sample rate mainly will control how much spectrum you will see on the graphical displays.

> On the Headphone jack of the Hermes?

The audio output on Hermes/Mercury is always at 48ksps.  The audio bandwidth is going to be whatever you tell PowerSDR.

> and into the PC via Ethernet, VAC?

Again, remember here that Hermes is giving you raw I and Q samples at whatever sample rate you choose.  Your PC is doing all of the final demod, filtering and decimation.  The FPGA in Hermes merely does some initial operations to bring the datarate down to an acceptable level for the PC to handle.  So, the audio is not generated inside the hardware, it's generated inside PowerSDR.  The audio that comes out of the headphone/line-out connector is generated on the PC and sent back to Heremes to play for you.  It could just as well have been sent to your local computer's soundcard instead.

> What are the proper PC port types. MME, DirectSound, WDM/KS 
> 
> What are the proper corresponding Bits per sample and number of channels for the VAC links in the PC.
> I am asking so as to avoid the overhead of format conversions when using VAC.

I can't comment on these issues since I'm not involved with PowerSDR.  I send samples to the system audio on the Mac as 48k stereo interleaved 4-byte floats.

> 
> What are the appropriate settings,( SR, BPS, NC)  for Input? Direct Mic and also VAC input?
> 
> 73
> 
> John
> TI4/N0URE


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