Re: PSK beacons on HF ?


Kristoff Bonne
 

Hi Siegfried, Graham, kd9jyk, all,


First of all, my apologies for the late reply (to much to do, to little time :-) )


I did not know this tool.
I'm a linux-user but I'll try if I can get it to run anyway.


Anycase, there are PSK31 encoders available for GNU Radio so I can generate a PSK31 signal inside GNU Radio. Also, there also exists a number of 'radio-channel' block to emulate a lot of the parameters like noise, fading multipath and so on.
However, I was just interested to see how well this all stacks up in real life, hence by question here.
I'll give it a try looking for PSK signals using the RBN. (*)


The reason I preferred a beacon-signal is that is transmits fixed on one frequency and transmits always the same text.
My idea was to let the receiver and the decoder run on that frequency for several days and monitor the Bit-error-rate of the decoder over a long period with different types of radio-condition. As a beacon continuously transmits the same text, I can  make a script to determine the BER automatically which should me it more easy to find the radio-signals where the decoder went belly-up.
(Yes, I'm a bit lazy. why look for bad decoding traces manually if you can write a computer-program to do that for you :-) )




(*)
As a side-note.
About using a websdr to download audio-samples to do PSK demodulation. Currently, I do not really understand how to do this.

A PSK decoder is based on phase-information, which means that you need I/Q signals (ok, perhaps not BPSK, but surely in higher-level PSK). However, audio-files are real numbers, i.e. only contain 'I' data. . So, how does this work?
How do you convert an single-channel audio-file into I/Q data?


I read some documents that you can do this by using "resampling:, using 2 sequential samples for I and Q, then ignore the next to, to get a I/Q at 1/4 the sampling-rate. I tried to simulate that in GNUradio, but I could not get this to work. I know it must be possible as all digital-mode applications do this, using the audio-port of the PC as input, so it can be done. But how?


Perhaps somebody who knows SDR better can explain this?




73
kristoff - ON1ARF

On 21/04/2020 12:43, Siegfried Jackstien wrote:
hmmm only for test i would use any digimode soft and "send" my own psk signal (only audio not rf)

that way you can test the decoder

or use wscgen (see picture)

that produces a test audio ... where you can add also noise ... so then testing of your decoder is possible also with noisy signal

if that works then just tune up to 20m over the day and you sure see several psk stations

dg9bfc sigi

Am 20.04.2020 um 22:00 schrieb Kristoff Bonne:
Hi Ev,



The question is not about the propagation data,

What I am looking for is a real HF PSK-signal to practice the PSK decoding process I learned in the GNU radio tutorial.
(see here: https://wiki.gnuradio.org/index.php/Guided_Tutorial_PSK_Demodulation)


Earlier, I did experiments with decoding FSK signals with GNUradio. For that, I used the RTTY transmission of the DWD at 147.3 KHz and navtex transmissions on 490 and 518 KHz as they provided almost permanent signals to do long-term tests of the decoder flowgraph.

So, now, I am looking for a equivalent PSK-signal on HF, MW of LW to learn building a PSK demodulator.





73
kristoff - ON1ARF


On 20/04/20 21:05, Ev Tupis via groups.io wrote:
Hi Kristoff.  The PropNET.org project provided 15 years of PSK31 signals on 30 and 10 meters.  It recently shut down.  Sorry.  However...all of the propagation that it recorded over that time is still recorded and can be visualized at http://www.PropNET.org

-Ev, W2EV






On Monday, April 20, 2020, 2:38:27 PM EDT, Kristoff Bonne <kristoff@skypro.be> wrote:





Hi all,


Quick question:
Are there beacons that transmit PSK signals continuously?


I'm currently learning GNU radio, currently tutorial 7 on the GNUradio
website on decoding PSK.
So it would be nice to have a real "live" PSK signal to try to decode.

So-far, I have two sources for PSK signals: the middle-frequency beacon
on QO100 and FM-RDS but I also like to have some "HF" signals to look at.
I think I remembering there used amateur-radio beacons that transmit PSK
signals instead of CW. Do they still exist?

Or are there other sources of PSK signals on HF that are more or less
permanent to receive?




73
kristoff - ON1ARF










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