[amsat-bb] DopplerPSK - No 1 kHz-autotracking radio tuning

Thu Jun 13 14:22:09 UTC 2019

Bob,

Yes they can correct too much smaller with CAT control, for NO-84 PSK
I have SatPC32 correct my IC-910 every 600Hz this doesn't appear to
present any problems and I've had many contacts.

Is there a reason why you're suggesting this isn't OK?

73,

Peter, 2M0SQL

On Thu, 13 Jun 2019 at 13:35, Robert Bruninga via AMSAT-BB
<amsat-bb at amsat.org> wrote:
>
> Question.  All FM-only rigs of course only do 5 KHz steps anyway.  Are we
> finding that multi-mode rigs when placed in FM mode can actually step
> smaller under CAT control?
>
> If so, then we must point that out to users, since it will not work for
> PSK31 even in FM.
>
> Thanks for the reminder.  If rigs do that, then I will add this to the PSAT
> web page.  The advice to not use auto-radio tuning except for 5 KHz steps on
> the downlink.  IE, not smaller steps.
>
> Bob, WB4APR
>
> -----Original Message-----
> From: AMSAT-BB <amsat-bb-bounces at amsat.org> On Behalf Of aflowers--- via
> AMSAT-BB
> Sent: Wednesday, June 12, 2019 10:58 PM
> To: amsat-bb at amsat.org; Scott <scott23192 at gmail.com>
> Subject: Re: [amsat-bb] DopplerPSK
>
>  Scott, Roy, Umesh, et al;
> Part of the problem with PSK31 is that it required the adjustment for
> changes in Doppler shift to be to be phase-continuous.  I think the Doppler
> rate (delta-Doppler shift) at even 10m is too fast for most radios--what you
> often get with CAT control, even if you can update while transmitting, is
> PSK31 that jumps more than 31Hz per update, and that totally destroys the
> phase continuity required to tell a '1' from '0'.  This was the "fun"
> problem that spurred me to take a swing at it over a summer vacation.
> When DopplerPSK applies "anti-doppler" on the transmitted signal, it does so
> at the baseband audio level.  This works fine for 3Khz passbands on a 10m
> uplink, but if you want to do it with SSB transponders and VHF and UHF
> you'll need an SDR where you aren't limited by an IF filter.   The same
> algorithm in DopplerPSK could be used on a complex signal in the SDR
> architecture, and it could work equally on TX and RX in the processing
> chain.   To the accuracy of the orbital elements everyone uses, if everyone
> corrects their uplink and downlink properly there is no perceived frequency
> drift by anyone using the satellite.  Just what you need for a GHz-range LEO
> with a narrow-band transponder, eh? Since the downlink of NO-84 is FM there
> is no Doppler shift in the baseband audio of the downlink--you hear what the
> satellite hears.  If we get a mode-K satellite it might be worthwhile to do
> a baseband demodulator in a soundcard since the total change in Doppler
> shift will be small enough to fit in a conventional HF radio's IF passband
> in both directions.
> If the antiquated hosting site doesn't come back I'll get off my duff and
> find a "proper" place for it.  It's nice to see people playing around with
> it. (Thanks for bridging the gap in the meantime, Peter.) Andy K0SM/2
>
>
>
>     On Wednesday, June 12, 2019, 9:24:12 PM EDT, Scott via AMSAT-BB
> <amsat-bb at amsat.org> wrote:
>
>  While it might certainly be possible to put together a solution that would
> compensate your uplink so that its corresponding downlink through the
> transponder holds stationary on a single spot on the downlink audio
> spectrum, there are two reasons (at least) that I can think of to not go to
> that trouble:
>
> #1, the DopplerPSK app takes care of it perfectly already.  The work has
> been done.
>
> #2, if memory serves, some radios do not respond to CAT frequency
> adjustments when transmitting.  In this mode, your uplink radio is
> transmitting non-stop for the entire ~10 minute pass.  If you have a
> hardware/software setup that can only change RF frequency when in receive
> mode, that will never happen during an NO-84 pass.
>
> Lastly, like much satellite work, the uplink and downlink are two
> completely separate discussions in this mode.  While the 10m uplink works
> extremely well with the DopplerPSK software and the HF radio of your
> choice, receiving & demodulating the PSK31 downlink can be done by any
> antenna/FM radio(or SDR), and computer combination of your liking.  Just as
> one example, my setup is:
>
> TX:  Windows PC > DopplerPSK > Signalink > FT-857d > MyAntennas EFHW-8010
>
> RX:  70cm X-Quad > SDRPlay RSP1 > HDSDR on Windows PC (doppler track w/
> Orbitron) > FLDigi
>
>
> -Scott,  K4KDR
>
> ==============================
>
> On Wed, Jun 12, 2019 at 8:20 PM k6vug at sbcglobal.net <k6vug at sbcglobal.net>
> wrote:
>
> > I'm very curious about this, thanks for sharing the links.
> >
> > Looks like the program adjusts the PSK modulation within the pass band of
> > the uplink, and at 10 meters, that would be relatively small.  It makes
> > sense, however would this work if SatPC32 manages the uplink ?
> >
> > Secondly, I came across this on the website:
> >
> > "DopplerPSK does not provide any PSK31 demodulation; you should use a
> > separate program for that purpose. DopplerPSK does not provide any
> > compensation for downlink Doppler (which you would need for fully linear
> > transponders)."
> >
> > Question 2 - why not use something like HRD for everything (doppler, psk,
> > rotator, logging, etc) ?
> > (I believe I tried it sometime back by routing of the downlink audio back
> > into HRD)
> >
> > 73!
> > Umesh
> > k6vug
> >
> >
> >
> >
> >
> > On Wednesday, June 12, 2019, 8:10:11 AM PDT, Scott via AMSAT-BB <
> > amsat-bb at amsat.org> wrote:
> >
> >
> > I originally used the link on 2M0SQL's excellent how-to page:
> >
> > https://www.2m0sql.com/2018/10/29/using-the-no-84-psat-psk-transponder/
> >
> > ... which is:
> >
> > http://www.frontiernet.net/~aflowers/dopplerpsk/dopplerpsk.html
> >
> > If that link isn't available, you're welcome to the copy I downloaded
> > which
> > has just been put at:
> >
> > https://www.qsl.net/k/k4kdr//downloads/DopplerPSK_0.2.zip
> >
> > -Scott,  K4KDR
> >
> > ==========================
> >
> > On Wed, Jun 12, 2019 at 10:53 AM Roy Dean via AMSAT-BB <amsat-bb at amsat.org
> > >
> > wrote:
> >
> > > With all this talk of NO-84, and me finally having a semi-operational
> > > ground station - I went looking for DopplerPSK, but every link I found
> > was
> > > broken.  Where can I get this software?
> > >
> > > --Roy
> > > K3RLD
> >
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