On 09/09/2016 06:40 PM, pen tester wrote: > Hi, > Still playing around and I have a question about the value which > should go in the Polyphase Resampler on the tx side please. Any advice > on the AM rx too would be helpful :-)
Looking at transmit. It appears you start with something in memory so call the initial pressure x - it will be likely be as fast as it can go. Next is a resampler which bumps up the sampling rate to x*32. Skipping the filter - which is a can of worms in itself - the next resampler bumps up the sampling rate to x*32*48. So before you get to the multiply, you appear to have some serious plumbing problem. Also, I wouldn't be calling math functions to calculate tap values on a filter. I'd recommend calculation those taps by hand inserting the values in the filter. I recommend simplifying it by calculating the everything in front of the first resampler and stick in a file - create a little back pressure. And then I would move the FIR filter on the side of the resamplers which you expect to have the highest sampling rate - which makes one of those resamplers redundant. Suppose you can suck in the contents of the file on the filesystem at a sampling rate of 32k. Then you would need a resampler which decimates at 32k and interpolates at 48k - or interpolates at 3 and decimates at 2 - to match 32k to 48k. Now the osomo sink is sampling at 1.2 Hz. My guess is the 1.2 Hz a mistake - you appear to have meant 1.2 MHz (or 1.2e6) in which case you need to interpolate at 25 and decimate at 1 to match 48k to 1.2M. Disclaimer: don't confuse me with someone who knows what they're talking about - I'm just making this up as I go along. It's simply what I would do to clean it - it may be wrong. > > Transmit > > * Simply trying make the working PSK31 audio tx to tx over HackRF > instead using [1] and updates from Tim's response > * Screenshot: http://pasteboard.co/1dLjHxMAU.png > > > Receive > > * Simply trying to make the working PSK31 audio rx work using a RTLSDR > instead based on [2] > * The first line is an attempt to take in the AM signal and just pass > it on to [2] > * For the AM rx, I used [3] as a guide > * Screenshot: http://pasteboard.co/1dLZWV9mv.png > > > [1] https://github.com/tkuester/gr-psk31/ > <https://github.com/tkuester/gr-psk31/> (examples/psk31_tx.grc) > [2] https://github.com/tkuester/gr-psk31/ > <https://github.com/tkuester/gr-psk31/> (examples/psk31_rx.grc) > [3] https://www.csun.edu/~skatz/katzpage/sdr_project/sdr/grc_tutorial3.pdf > <https://www.csun.edu/%7Eskatz/katzpage/sdr_project/sdr/grc_tutorial3.pdf> > > On 6 September 2016 at 05:49, pen tester <testerofp...@gmail.com > <mailto:testerofp...@gmail.com>> wrote: > > Tim, > Yes, your graphs are really useful :-) Thank you for responding > in such detail! > > Here is what I am up to: > > Transmit side: > > * I made your changes to your transmit graph [1] > * All the changes were fine but I was confused about the use of > the Polyphase Resampler as I could not get the values to work > without underflows when executing i.e. "UUUU..." > * So instead (this is probably wrong) I tried using a Rational > Resampler with an Interpolation of 1e6 and a Decimation of 48e3. > * Updated version: http://pasteboard.co/hmyGOGTE4.png > <http://pasteboard.co/hmyGOGTE4.png> > * Either way, the tx graph looks healthier - just need some advice > on the resampler perhaps? > > > Receive side: > > * I am using the start of this receive graph [2] as it was using > radio rx already > * and just modifying the demod portion to be more like your rx graph > * Updated version: http://pasteboard.co/hmzrMBAIi.png > <http://pasteboard.co/hmzrMBAIi.png> > * I also need advice from anyone who could point in the right > direction on the AM rx side please? > > > [1] https://github.com/tkuester/gr-psk31/ > <https://github.com/tkuester/gr-psk31/> (examples/psk31_tx.grc) > [2] https://github.com/argilo/sdr-examples > <https://github.com/argilo/sdr-examples> (tutorial/6_psk.grc) > [3] https://github.com/tkuester/gr-psk31/ > <https://github.com/tkuester/gr-psk31/> (examples/psk31_rx.grc) > > On 4 September 2016 at 12:33, Tim K <tpkues...@gmail.com > <mailto:tpkues...@gmail.com>> wrote: > > Hey hey! > > Glad to see someone using this. (And that it's apparently still > working! Goodness... I need to clean this up...) > > I'm giving advice freehand right now, as I don't have my radios > with me to test this. There are definitely more elegant ways for > this solution, this is just the quickest I could think of > without reverse engineering what I wrote forever ago. > > Since this is AM, I think you'll only need the Real port on your > "Float to Complex" block. You can attach the "Null Source" to > the Imaginary port. Do a quick check to make sure the real > signal's not exceeding +/- 1... you might want to attenuate it > to +/- 0.7 for now, someone else should comment. > > As far as the transmit side goes, I'd leave everything up to the > "Multiply" block untouched. Consider that your "audio input" to > the radio. After that... > - Multiply Const (set to 0.7 for safety) > - Polyphase Resampler (float/float) set to (1e6 / 48e3) - This > gets your sample rate up to radio speeds > - Float to Complex (in the Real port, Null Source to the Imag > port) - This makes your signal "complex AM" > - Send the Complex stream into your Osmocom Sink (set to 1e6 > sps) - And transmit! > > If I remember correctly, some radios don't like working at > non-integer sample rates. (The hackRF may be ok though...) > > Play gently with your TX gain until you can see it on another > radio. (IIRC the HackRF is simplex... perhaps an RTL?) Use AM to > demodulate. > > I've been meaning to do a write up on this for a while. If I > ever get around to it, I'll make sure to CC you. > > - Tim > > > On Fri, Sep 2, 2016 at 11:55 PM, pen tester > <testerofp...@gmail.com <mailto:testerofp...@gmail.com>> wrote: > > Hi, > I am trying to get a simple working example of PSk31 working > (transmitting with a hackrf and receiving with a rtlsdr > dongle). Here is what I have so far. > > > Working PSK31 tx and rx with a sound card > ========================================== > Transmit: https://github.com/tkuester/gr-psk31/ > <https://github.com/tkuester/gr-psk31/> (examples/psk31_tx.grc) > Receive: https://github.com/tkuester/gr-psk31/ > <https://github.com/tkuester/gr-psk31/> (examples/psk31_rx.grc) > > These work great for sending a PSK31 message over audio card > and receiving with the audio card. > > I just slightly modified them to take input from the "Audio > Source" block instead of a "Wav File Source" to use the > sound card directly: > > Transmit Graph: > http://www.megafileupload.com/7sm9/psk31_tx.grc > <http://www.megafileupload.com/7sm9/psk31_tx.grc> > Transmit Image: http://pasteboard.co/giNm3kNzC.png > <http://pasteboard.co/giNm3kNzC.png> or > http://www.megafileupload.com/7smc/psk31_tx-audiocard.png > <http://www.megafileupload.com/7smc/psk31_tx-audiocard.png> > > Receive Graph: > http://www.megafileupload.com/7sma/psk31_rx.grc > <http://www.megafileupload.com/7sma/psk31_rx.grc> > Receive Image: http://pasteboard.co/giOlxtWUf.png > <http://pasteboard.co/giOlxtWUf.png> or > http://www.megafileupload.com/7smb/psk31_rx-audiocard.png > <http://www.megafileupload.com/7smb/psk31_rx-audiocard.png> > > Turning up the audio a little and tuning to 2003 approx on > the rx graph results in reception of the sent message "Hello > World!" > > > > Reference version for using hackrf instead of sound card > ========================================================== > Next, I wanted to modify these to audio versions to work > over Radio using a HackRF and RTLSDR dongle. > > These graphs seems very useful but I couldn't get it working > end to end for some reason. > > Transmit: https://github.com/argilo/sdr-examples > <https://github.com/argilo/sdr-examples> (multi_tx.grc) > Receive: https://github.com/argilo/sdr-examples > <https://github.com/argilo/sdr-examples> (tutorial/6_psk.grc) > > I made some changes to the freq to be in range for RTLSDR > .e.g changed freq from 441e6 in ref graph, changed to 841e6. > > > > My merged attempt > ================= > The attempt I am currently trying to get working is based on > the audio soundcard flies for the transmit: > > Transmit: Using audio tx (psk31_tx_attempt2): where I just > replaced the audio sink with the Osmocom sink (not sure what > else is needed here for transmission over hackrf) > > Transmit Graph: > http://www.megafileupload.com/7smi/psk31_tx-attempt2.grc > <http://www.megafileupload.com/7smi/psk31_tx-attempt2.grc> > Transmit Image: http://pasteboard.co/giOMGNqD9.png > <http://pasteboard.co/giOMGNqD9.png> or > http://www.megafileupload.com/7sme/psk31_tx-attempt2.png > <http://www.megafileupload.com/7sme/psk31_tx-attempt2.png> > > Receive Graph: > http://www.megafileupload.com/7smh/6_psk-hackrf.grc > <http://www.megafileupload.com/7smh/6_psk-hackrf.grc> > Receive Image: http://pasteboard.co/giPflR4TI.png > <http://pasteboard.co/giPflR4TI.png> or > http://www.megafileupload.com/7smf/6_psk_hackrf.png > <http://www.megafileupload.com/7smf/6_psk_hackrf.png> > > For the receive, I just left radio rx part in and replaced > the decoder parts with decoding logic from > https://github.com/tkuester/gr-psk31/ > <https://github.com/tkuester/gr-psk31/> > (examples/psk31_rx.grc). I made other minor changes such as > freq and sample rates. > > > > My question > ============ > So in summary, just looking for a little guidance on my > merged attempt to get psk31 out over a hackrf and received > using a RTLSDR. Any advice for a learner would be great :-) > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org <mailto:Discuss-gnuradio@gnu.org> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > <https://lists.gnu.org/mailman/listinfo/discuss-gnuradio> > > > > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
