It's all about the Software

Hello Simon,

Today I was doing some terrestrial work on 10.368.100 Mhz using an Octagon LNB for receive. As you know the Octagon does have some drift. Thinking on how you use the QO-100 BPSK beacon to provide a reference to stabilize the frequency I was wondering if it would be possible to implement a user supplied reference signal.

I can generate a GPS-DO locked carrier at 10.368 Mhz (or other frequency). Could you then use that as a reference to tame the LNB drift? Or would you need something more than a simple carrier?

I was using a carrier on 10.368.000 today, with the calibration window open and manually tweaking the calibration as the LNB drifted. It worked, but it was not elegant, hi.

As always, thanks for your fine work.

regards, Roy

Hi,

Maybe this could be done, but why not change the LNB's TXCO or use an external reference?

Hi Simon.

Certainly there are other options but it occurs to me that using the reference frequency idea could allow use of any unmodified equipment, not just LNBs but also transverters or converters that might be difficult to stabilize internally. I think it could make life a lot easier for users of such equipment to have the software handle the drift issue.

I was using a GPS-DO modified PlutoSDR running the Satsagen program to generate the 10Ghz signal (third harmonic). Since the Satsagen signal generator will go from 50Mhz to 26Ghz, it makes for a very versatile reference marker.

regards, Roy

ROY-VE7DH wrote: Mon Sep 21, 2020 4:30 pm Hi Simon.

Certainly there are other options but it occurs to me that using the reference frequency idea could allow use of any unmodified equipment, not just LNBs but also transverters or converters that might be difficult to stabilize internally. I think it could make life a lot easier for users of such equipment to have the software handle the drift issue.

I was using a GPS-DO modified PlutoSDR running the Satsagen program to generate the 10Ghz signal (third harmonic). Since the Satsagen signal generator will go from 50Mhz to 26Ghz, it makes for a very versatile reference marker.

regards, Roy

I agree but my priorities lie elsewhere for Q4 2020 / Q1 2021, especially as you do have a relatively cheap solution available now.

No problem, Simon. It was not an urgent request, rather something that I think could only be done with SDRs and software, therefore interesting.

regards, Roy

Hi Simon,

Another thought (which has probably occurred to you) about a possible reference frequency option.
I Use a Raspberry PI as a WSPR transmitter and monitor my transmissions using the AirSpy HF+ and your great software. The HF+ drifts some while it is warming up, really not bad, but it is a problem when viewing WSPR transmissions which must be in a 200 Hz wide band. The drift makes some of my transmissions appear to be out of band even though they are not, as the RPi WSPR software uses NTP to generate a ppm frequency correction which assures that the transmission is on the indicated frequency.
Perhaps a similar NTP technique could be used in the SDR Console to provide (selectable?) periodic frequency correction. FYI The RPi WSPR TX software using the NTP frequency correction function is at: Https://github.com/JamesP6000/WsprryPi.git The last paragraphs of the ReadMe file contains useful references and credits.
Much appreciate your SDR Console work. Another donation will be coming your way at the 12/1 update.

73

Tom K4ZAD

Your PC clock is probably accurate enough for this without bothering with NTP. I could probably correct based on received bandwidth, but not in 2020. Remind me next year and I'll look at this.

Run ntp software on your PC. That will do about as well as can be done on a PC. It will not correct for any errors in your AirSpy HF+ or any other front end. That requires external GPS lock.

{^_^}