Interfacing GnuRadio with rpitx

[UgoPoddine]

Hello András,

I'm a bit confused regarding interfacing of GnuRadio with Evariste's RPITX, and I hope you can help. I have used your test SSB flowgraph (but the effect is the same with several others and with CSDR tool also) for modulating in USB audio files and transmitting them over RPITX. The situation is the following :

1. I'm using RPITX "standard version" (not the new one) installed on a RaspberryPI2 with Stretch (Linux 4.14.49+ #11201 armv6l GNU/Linux)
2. test trasmission over RPITX on USB of sampleaudio.wav test file, modulated using the Evariste's modulation program pissb is successful over 10 m band
3. I made a test flowgraph on GnuRadio on Windows that reads the "modulated" (by pissb) wav file and send it to the RaspberryPI via UDP sink : this allows an RPITX correct transmission, but only if I use the following receaving statement :

nc -u -l 8011 | sudo rpitx -i - -m IQ -a 14 -f $FREQUENCY

Gnuradio reads in FLOAT format and send it to UDPsink in FLOAT format (not in COMPLEX)

4. If I start modulating the sampleaudio.wav using your test USB TX flowgraph or other USB TX flowgraph or CSDR and I send the modulated output (correct, checking FFT scope...) to RPITX using again UDP sink, the result is a noise transmission (both setting RPITX in IQ or IQFLOAT format, both transmitting float or complex data flow over UDP sink.

Worst, the "correctly running" output of PISSB utility can be played using any kind of playing audio tool, while the modulated output of the different flowgraphs (being IQ) should not. I'm consequently a bit confused : what is the real data format accepted as input from RPITX, and which the correct way for interfacing it with Gnuradio ? (I guess that UDP or TCP sink - now deprecated - is not the issue...)

Any help appreciated Regards, 73 Ugo

[ha7ilm]

Ugo,

It has been years ago I last played with that, so I don't know. Since then, @f5oeo could have changed stuff in rpitx as well, including its command line parameters.

Andras