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TX synchronisation at special Pluto-setup

Also known as ADALM-PLUTO.
Posts: 2
Joined: Tue Sep 22, 2020 12:35 pm

TX synchronisation at special Pluto-setup


Unread post by dl2fw »


I’d like to ask for the following additional feature / option :

But first a description about what I did:

I developed a small add-on board for the Pluto which delivers some pretty accurate 40Mhz to the Pluto (Tailor Winfield VCTCXO) – I have a small board-documentation at the Amsat board….
From this 40MHz VCTCXO I also derive on the same board the 25MHz for the LNB.
The board is currently in use by ~ 10 users.
It can be locked to an external GPSDO to get down to the last Hz – in this case everything is fine – no deviation at Pluto or LNB, RIT/XIT=0.

But in this setup the GPSDO is not really necessary!

We have the Beacon!

Because now everything is based on one single oscillator and while using the beacon correction, we know the (small, ~1-2Hz) deviation of this oscillator.
The missing part is: Calculating the relative beacon deviation (relative!, everything is linear in the mixing process) and correct the transmit frequency by this factor (usually << 1ppm).
This additional option in beacon/pluto mode would make it possible to correct RX and TX by the beacon without the need for a GPSDO.

What do you think?

I know – this would be only of use for guys using the special setup, that LO for the pluto and LNB are derived from the same oscillator…
Any chance this option could be added in an upcoming version?

73 Michael – DL2FW

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Simon G4ELI
Posts: 1364
Joined: Thu Aug 06, 2020 7:27 am
Location: Mawnan Smith

Re: TX synchronisation at special Pluto-setup


Unread post by Simon G4ELI »

Maybe, but I'm taking a break from SDR Console in October to learn some new programming - web interfaces etc.

As we have a working solution it would be easier to use what we have now?
Simon Brown :shock:

Do not send me direct e-mail, thank-you!

Posts: 2
Joined: Tue Sep 22, 2020 12:35 pm

Re: TX synchronisation at special Pluto-setup


Unread post by dl2fw »

Hi Simon,

It is really not essential as everything is working very nice!! Would just be a nice option.

BTW 2or 3 years ago I did some work on noise reduction and ported the Ephraim Mallah algorithm to a STM32 stand alone noise reduction board. During this time I was in contact with Warren Pratt who implemented the same algorithm to. PowerSDR. The involved math took me a big amount of time to go through it... as on this board samplerate and fft width is flexible, it was important, to keep the speech and noise detection time constants close to 70ms...
Good to see, that this algorithm also made it to the SDR Console.
I have one question regarding this: Musical Noise appearence when setting the reduction parameter above app. 10dB can be dramatically reduced by a special coefficient treatment just before the ifft. With this musical-noise-reduction a setting of up to 20dB shows no musical noise and a very good reduction behavior.
Do you know, if this is already implemented?
73 Michael

Posts: 29
Joined: Sat Aug 08, 2020 10:43 am

Re: TX synchronisation at special Pluto-setup


Unread post by dg9bfc_sigi »

hello michael ... maybe ask again in a second thread if simon added that musical noise reduction ... does that reduce (maybe complete eiminate??) the noise that is like "plätschernder bach" ?!? if yes ... then the noise reduction would be much better (its allready quite good)
greetz sigi dg9bfc

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