SDR# or HDSDR and a 'discriminator tap' output ?

[mr.sneezy]

A question out of the blue. 

I wonder if anyone knows if the audio output from the  SDR# or HDSDR software can deliver the same raw unfiltered audio as a  discriminator tapped analogue scanner can ?

The reason I ask is that I have an interest in decoding weather sondes (balloons), and the digital types send GFSK in narrow band. The best software around to record sonde data and track them in real time (SondeMonitor) needs a discriminator tapped audio input to a PC sound card. 

Thanks,

Martin

[ekow]

Yes it can.
with SDR# you can set wether the audio output will be filtered or not.
also you can set the if filter width.

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[jdow]

What kind of discriminator? They all produce slightly different results
when the rubber meets the road.

The NFM output with audio filtering turned off should do pretty well for
a sonde sort of device.

{^_^}

[jdow]

There seems to be no setting for preemphasis/deemphasis compensation.
I think that's what the fellow is worrying about. For NFM I don't think
they have any deemphasis on the FM audio. I'd suggest he simply try it
and find out for himself. It's a mercifully cheap experiment.

{^_^} Joanne, W6MKU

On 2012/10/02 04:43, ekow wrote:
> Yes it can.
> with SDR# you can set wether the audio output will be filtered or not.
> also you can set the if filter width.
>
> On Tuesday, October 2, 2012, mr.sneezy <mr.s...@bigpond.com

> <mailto:mr.s...@bigpond.com>> wrote:
> > A question out of the blue.
> > I wonder if anyone knows if the audio output from the SDR# or HDSDR software
> can deliver the same raw unfiltered audio as a discriminator
> tapped analogue scanner can ?
> > The reason I ask is that I have an interest in decoding weather sondes
> (balloons), and the digital types send GFSK in narrow band. The best software
> around to record sonde data and track them in real time (SondeMonitor) needs a
> discriminator tapped audio input to a PC sound card.
> > Thanks,
> > Martin
> >
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[mr.sneezy]

Thanks for the input guys.

I didn't think the AF filter switch would do what I needed, but I tried it out as suggested...

Result = WINNER :)

SondeMonitor was quite happy to decode the Vaisala RS92-SGP sondes data from audio delivered by SDR# and my R820T tuner dongle !

The best setting actually seemed to be with the AF Filter box ticked (e.g. ON). SondeMonitor shows an audio oscilloscope view of received audio and the waveform looked better to me with it ON. 

SondeMonitor started recovering the sondes calibration data and weather sensor data right away.

I adjusted SDR# filter bandwidth to 8000Hz to fit the displayed spectral envelope plus a few percent. I left the other settings default, and I have the filter type to 'Blackman-Harris' (although I have no idea which filter is best for this GFSK signal). 

This is what I'm getting excited about

http://www.vaisala.com/Vaisala%20Documents/Brochures%20and%20Datasheets/RS92SGP-Datasheet-B210358EN-E-LoRes.pdf

These things drop into the desert once a day after a mission for the government weather bureau, they get up to 30km altitude and can go 180km down range at times. They send their GPS location data as well as sensor data...

Getting back to SDR# and my dongle. It seems that the R820T dongle is actually more sensitive than my old wideband scanner (with it's tapped discriminator). So for logging the sonde balloon flights or sonde chasing, the dongle looks better and a lots easier to use. 

The only issue is that I used two PC's to do this, one with SDR# running (desktop), and one with SondeMonitor running (a Netbook).

I wonder if I can use one PC to do this, preferably a laptop for portability. I guess I'd need something with real CPU grunt (which my Netbook doesn't have).

Cheers,

Martin

[jdow]

Look up "Virtual Audio Cable".

{^_^}

[mr.sneezy]

Thanks for the tip.

I gave up with it after about half an hour on Google though. No free versions to be found, and the trial versions have a nag voice mixed in to the audio every few seconds. 

I also found out some info that certain motherboards have a stereo mix that when enabled will loop main output to input for you, ASUS I think.

Later sometime I'll try a real audio cable from Line Out to Line In/Mic In and see if that just works.

[jdow]

You can probably get a short male male cable and look the audio out to
the audio in on your sound card, too.

{^_^}

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[DJ0MY]

Hi Martin,

I am running Sodemonitor with HDSDR without any problems on the narrow band SGP sondes...

I adjust the IF bandwith to around 8-9kHz BW (approx. double TX bandwith) for best decoding results.
Wider bandwidth will just worsen your signal to noise ratio.

Cheers,

Oscar

[mr.sneezy]

Hi Guys,

I did end up trying a male-male 3.5mm stereo cable from Line Out to Mic In on the Netbook, and it worked out very well. So VAC or other audio looping software was not needed in this case. I also found a 'Stereo Mixer' setting in the audio control panel, but that did not work for me. So patch cable it is.

I waited till Sunday morning when the local Meteorology people launch a RS92-KL analogue sonde. The RTL2832U+R820T type dongle pulled the analogue sondes wideband FM signal out very well. The local sonde is on 401.6Mhz normally. 

I got a screen shot of the spectrum and waterfall for record. I'll have to wait to try reading a digital sonde in actual flight, as they launch 400km from here.

The little N450 CPU in my netbook his 100% load momentarily when SondeMonitor is running, so there are error hits on the sonde sensor traces. I need something portable with more horsepower. With only SDR# running it is steady and clear audio (CPU at about 80%).

I really like the use of SDR# plus SondeMonitor on the same PC, it's a great demo of the power SDR of the technology combined with other end-user software. On top of that the cost of the sonde recording setup is stupidly cheap compared a hardware only radio receiver setup !

Cheers,

Martin

On Sunday, October 7, 2012 9:19:37 AM UTC+10:30, DJ0MY wrote:

Hi Martin,

I am running Sondemonitor with HDSDR without any problems on the narrow band SGP sondes...