Re: PSK beacons on HF ?
Hi Siegfried, Graham, kd9jyk, all,toggle quoted messageShow quoted text
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?
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)