NB Station for Es'hail-2

So long as you can receive one or other beacon within the passband (and it's CW), a single stick software drift connection is possible. I have some gnuradio code that does just that (although I'm using my Ettus USRPs, but the same code could be used with a dongle

Whether a tablet would appreciate the extra overhead of gnuradio is another matter of course.

For those interested, Basically I take 250k of B/W, Filter and Decimate around the 'beacon', then send to a FFT, measure the 'strongest' bin, calculate what that frequency is, compare against the 'correct' frequency, and send the difference back to the USRP or Frequency Translating FIR Filter (otherwise known as the Virtual Big Tuning Knob!)

In the case of a dongle, it would need to be the FIR Filter, as the drivers in gnuradio don't let you change the frequency of the device once set without stopping and restarting the flowgraph.

Note, my code will go down to 250mHz (Yes, milliHertz). Overkill, yes (although not for some of the experiments I intend to do), but remember that when the beacon is in PSK mode, there will of course be frequency shifts every time the phase changes to deal with. I'm hoping at least one beacon will always be in CW mode

Iain

Quote from DL3DCW

Now the software drift correction also works fine with weak master signals like the lower engineering beacon at 10-12dB S/N.

Hi DL3DCW,

i managed to get my 2 Stick solution to work with a reference signal level <6db.

Even the now weaker lower EB is locked without problem.

VY73 DB8TF

g7iii : Very interesting! Concerning the necessity of a CW carrier/signal, I wonder if a PSK-beacon couldn't be used too? E.g. by locking to one of the (known) carriers, some 'averaging' & 'secret sauce' , assuming the beacon is 'bang on' frequency of course.

Quote from DL3DCW

I am very satisfied that the software correction works so well.

Thats exacly the same thought i had as i saw the prototype working here on the table a few months ago

DL3DCW

It is a nice solution !

Is it working with another sdr sticks than nooelec ? like standard rtl-sdr sticks

Do you need some beta testers ? If you have a sd file image to share I can test if you agree.

Thank you.

73's

ON7KGK: you can use any rtl-sdr stick but it is better to take ones with 0,5ppm tcxo.

First i used normal SDR Sticks but they drift a little, with the TCXO sticks the results are much better

Vy73 DB8TF

On a final 1-Stick solution no more TCXO Sticks are needed

I really like this solution. This ensures us a good stability on the downlink. But what happens if an uplink station is not stable in the same way? We are forced to follow the correspondent and our reception stability is relative.

Or not?

Ciao, Lucio

I hope the comming AMSAT beacons are stable enough to lock on

How the different hams manage their uplink stability is another story...

Also i like to participate in this project. Will order 2 SDR sticks as well as a raspberry pi just now. Hopefully everythings will work fine after the opening party at the groundstation of Amsat-DL.

I am still searching for somebody who can write a sdr# plugin for the 1-stick solution, or for any other SW running on M$.

Simon from SDR-Radio said he will look at a this function for his SW but that takes some time and he has much more features to implement prior to this.

My 2PC + 2Dongle + external controller solution works well but a easier solution would be great.

vy73 DB8TF

DB8TF hi Flo.. you should ask Manawyrm here for that.. He already wrote a plugin for ADALM Pluto for SDR#

DL3DCW, Will you publish source code for drift correction app? It would be very interesting. Right now I stuck with GRC simulation. Something is working, something is not working.