On 11/01/2017 01:55 PM, Adrian Hodgson wrote: > Thanks for responding I have posted responses within the text. > > On Wednesday, 1 November 2017 20:04:57 GMT Cinaed Simson wrote: >> On 10/30/2017 04:04 PM, Adrian Hodgson wrote: >>> Quite new to this so perhaps a dumb question. >>> >>> I have the following flowchart Narrow_band_QT.grc and screenshot attached, >>> just something I have been playing with. >> >> Note, you should set the RF again to 0 when receiving. There's frontend >> on the hackrf and you run risk of smoking the receiving RF amplifier if >> there's a strong RF transmission nearby. >> Also, the RF gain is either 0 or 1 - on or off. >> >> See the hackrf tutorials greatscottgadgets.com website. >> > Not a problem for me most of my testing is done with my test set, the RF gain > set at 14 dB means I can receive signals down to -115 dBm, I tend to use > signals at around -80 dBm so I am far away from the -5 dBm maximum for the rf > amp. > I did have a play with my wireless doorbell following on from the smart > gadgets tutorials and eventually got it to work, but my main use would be > monitoring the local amateur repeaters, being a licensed radio ham! > >>> There are a few variables I use one is band_width. Now the strange thing >>> is if I start with a default of 100KHz band width when running I can >>> scroll down to 10 KHz bandwidth and then go back up again, but if I start >>> with the default set to 10 KHz bandwidth it will not scroll up to 100KHz. >>> It is more noticeable when looking at the bandwidth tab which is directly >>> after the rational resampler. one can see the pass-band chance width as i >>> change the bandwidth. >> >> The bandwidth is equal the sampling rate - in your case - 2M. > > I think I did not explain myself correctly > > I did find two issues with my flow chart, one was that I used one variable to > feed another variable, so removed that issue. > > The second was the QT freq display sample rate after the resampler should > have > been at 240kHz not 2M. When set to 2450K then the frequency display matches > the true frequency.
240 KHz is the output sampling rate of the resampler - which matches the quadrature rate - or input sampling rate of the nbfm block. > > But that still did not resolve the issue I am having. If I set the default > band_width variable to 100e3 and run the flow graph, if you go to the > band_width tab and scroll on the bandwidth number you will see the width of > passband signal reduce and go back up as you scroll. > > But set the default band_width to 10e3 and run the flow graph and it does not > work. Okay, I think I know what you're doing - I didn't look inside the resampler block the last time. If you scale the interpolation in the resampler block, you change the output sampling rate of the resampler block - which no longer matches the quadrature rate - or the input sampling rate of the nbfm block. In short, the plumbing is screwed up. You need to scale the quadrature rate - or the input sampling rate of the nbfm block so it matches the output sampling rate of the resampler block after you re-scale the interpolation. -- Cinaed > > Attached are modified files. > > The grc should run with a rtl2833 as well as a hackrf one, at least I believe > so as I use the osmocom source block. > >> >> Look at with hackrf WBFM tutorial greatscottgadgets.com website. >> > Went through that. > >> The channel width of the NBFM is roughly 12-16 kHz - or even 20 kHz >> depending on which part of the RF spectrum your working. > > Granted but the demod is working all the way up to 100KHz bandwidth or 20kHz > mod, the paramters change as I change the the counters. >> >> The Power Squelch may not work on the hackrf - I tried it awhile back >> and I couldn't get it to work. But things have changed since then so >> your mileage may vary. > > Yes it does work for me. >> >> The only parameter you may be able to change reliably using a runtime >> slider on the hackrf may be the center and offset frequencies - provided >> the offset frequency is within the center frequency +- sampling rate/2. >> >> I did play with sliders on the frequency and sampling rate but I had >> trouble - and since I didn't need it - I didn't pursue it. That was a >> couple of years ago so thing may have changed. And if I recall correctly >> it was changing the runtime sampling rate which gave me trouble. >> >> You should post your hackrf questions on the >> >> hackrf-...@greatscottgadgets.com > > Will do. > >> >>> I am using it with hackrf one, to which I will have several questions >>> about >>> but will leave that to a later post. >>> I am lucky in that I have things like a spectrum analyzer and radio test >>> set to work things through with. I am slowly working through the >>> tutorials and a book called Practical Signal processing, perhaps my age >>> but finding it hard going especially when it comes to Python, cmake, and >>> some of the mathematics! >>> >>> Anyway if anyone can let me know why I get the results I do I would >>> appreciate it. >>> OS is SUSE Leap 42.3, GNU radio is 3.7.11, just in case that makes a >>> difference. >>> Cheers >>> Adrian > > > One of the next steps will be to get the dsd blocked installed if I figure > that > out, one of the local repeaters is either analogue or digital I believe. > > Thanks > > Adrian > > > > _______________________________________________ > 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