Learning how to use visual programming - psk31 codec

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Tinkerer2016
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Joined: Sun Jun 26, 2016 10:31 am

Learning how to use visual programming - psk31 codec

Post by Tinkerer2016 » Thu Jun 30, 2016 7:00 pm

I'm trying to learn visual programming. My goal is to create a psk31 encoder and decoder for 80m (3.5 MHz), decode and send a test signal.
For transmitting I will have to use a RF amplifier which I will build on a breadboard.

DVE
Posts: 18
Joined: Tue Sep 06, 2016 7:48 pm

Re: Learning how to use visual programming - psk31 codec

Post by DVE » Thu Sep 15, 2016 6:23 pm

Its a pity to say, but it looks like Red Pitaya board is not suitable for PSK.

This "sine wave" is generating by RP standard generator, was received by another receiver SDRPlay:

Fixed: the issue was in power supply, changing to another one fixed the problem
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Last edited by DVE on Thu Sep 15, 2016 11:17 pm, edited 3 times in total.

pavel
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Re: Learning how to use visual programming - psk31 codec

Post by pavel » Thu Sep 15, 2016 8:15 pm

Hi DVE,

I've sent you a long e-mail with a couple of ideas about what could be the source of this kind of problem and with some links to other test results.

In short, I'd say that it could be a power supply problem or the output of the Red Pitaya board that is not loaded with 50 Ohm. If it's something else, I'd be very interested to find the source of this problem.

Could you try to generate test signals using the SDR transceiver compatible with HPSDR and PowerSDR mRX PS? As far as I know this combination is known to work (at least with the 0.95 versions of the Red Pitaya ecosystem).

Best regards,

Pavel

pavel
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Joined: Sat May 23, 2015 5:22 pm

Re: Learning how to use visual programming - psk31 codec

Post by pavel » Thu Sep 15, 2016 8:48 pm

For comparison. Here is a two-tone signal generated by Red Pitaya and received by FLEX-6500:
Image

Test was done by Ger Metselaar (PAØAER). More information about this test can be found at the following link:
http://www.pa0aer.com/projecten/red-pitaya

DVE
Posts: 18
Joined: Tue Sep 06, 2016 7:48 pm

Re: Learning how to use visual programming - psk31 codec

Post by DVE » Thu Sep 15, 2016 10:46 pm

Thanks for your answer.

I used 3 programs as a signal source:
- standard Oscilloscope/Generator web app
- "generate xxxx" command line
- your wspr transmitter
Result is the same, and your gypothesis about power supply seems nice, I'll check it.
I cannot test HPSDR, its not working with my WiFi speed.

At first I was really frustrated with the signal quality, even 8bit HackRF is much better. But maybe its really a power supply issue.

Antenna is ok, it's a magnetic loop, tuned to SWR = 1.5 on this frequency.

DVE
Posts: 18
Joined: Tue Sep 06, 2016 7:48 pm

Re: Learning how to use visual programming - psk31 codec

Post by DVE » Thu Sep 15, 2016 11:19 pm

Pavel, thanks again, you helps me the 3rd time :)
Problem really was in a power supply, I powered RP from USB, and got a nice spectrum.

I think it would be nice to mention in the description, that standard PR power supply is not suitable for producing radio signals.
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pavel
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Re: Learning how to use visual programming - psk31 codec

Post by pavel » Fri Sep 16, 2016 8:35 am

Good news! I'm glad that transmission is finally working for you.

However, now when we know that this kind of problem is related to the power supply, we should find a way to define what power supplies are OK.
I powered RP from USB, and got a nice spectrum.
Do you have now all three radios (SDRPlay, HackRF and Red Pitaya) powered via USB from the same computer?

I'm not sure but it still could be that the problem is with the USB of the computer. It could be that when all three radios are powered from the same source, then they ride on the same 50 Hz interference and it cancels out.

So, if I'm not mistaken with the previous statement, then the key test would be when you power all three radios from independent isolated power sources (two computers?).
I cannot test HPSDR, its not working with my WiFi speed.
Have you tried the lowest sample rate (48000)? In PowerSDR mRX PS, it can be changed via Setup -> Audio -> Sample Rate.

DVE
Posts: 18
Joined: Tue Sep 06, 2016 7:48 pm

Re: Learning how to use visual programming - psk31 codec

Post by DVE » Fri Sep 16, 2016 8:46 am

pavel wrote:Do you have now all three radios (SDRPlay, HackRF and Red Pitaya) powered via USB from the same computer?
Yes, I powered all radios from USB, but not at the same time.

Dirty signal was only from standard Red Pitaya power source.

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