Great! Thanks! I'm very curious! br/vy73 markus dl8rds
Am Freitag, den 31.07.2015, 14:34 -0700 schrieb Chris Kuethe: > OK, I have a mostly working flowgraph and am now adding comment to all > the blocks explaining why I'm doing this or that. Will publish tonight > or tomorrow. > > On Tue, Jul 21, 2015 at 11:56 AM, Chris Kuethe <chris.kue...@gmail.com> wrote: > > Maybe I'll do up an illustrated example on this using NOAA weather > > radio, or the pager band > > > > On Tue, Jul 21, 2015 at 11:42 AM, <mle...@ripnet.com> wrote: > >> I just use the built-in firdes stuff, rather than using an external > >> designer. > >> > >> > >> > >> > >> > >> > >> > >> On 2015-07-21 14:38, Marcus Müller wrote: > >> > >> Hi Rich, hello Markus, > >> > >> On 21.07.2015 19:51, Richard Bell wrote: > >> > >> GNU Radio has channelizers built-in, but I've not used them yet, so I don't > >> know how far they take you into this kind of task. > >> > >> the Polyphase channelizer is actually an implementation derived from that > >> school of thought, and it works amazingly well. > >> In fact, in preparation of a presentation at a certain ham conference, I > >> tried using it to get 20 PMR/LPD channels out of a 1MS/s signal in real > >> time, and then just shuffle them around, before feeding them back into the > >> inverse synthesizer PFB. > >> > >> It's pretty easy: > >> Design a single low pass filter, as if you just wanted to filter out the > >> channel which is centered exactly at your RF center frequency, i.e. 0Hz, > >> with the full sampling rate [2], using the gr_filter_design tool. Play > >> around with the different window types[1], and bear in mind that the > >> suppression outside your desired passband needs to be high enough so that > >> the sum of the energy in all other channels don't hurt your channel too > >> much, but don't overdo it (60dB suppression should be enough). > >> Now you get a long filter. Copy and paste the filter coefficients from > >> gr_filter_design to your PFB filter taps property. > >> Set your channelizers number of channels according to your plans -- 40, if > >> you want to get all the 40 25kHz channels in 2MHz. You get a block with 40 > >> outputs! > >> Explaining things like channel mapping is best done by pointing you at the > >> official documentation: [3] > >> > >> > >> Greetings! > >> Marcus > >> > >> [1] Hamming is not always the best choice, I'd try that, Blackman-harris, > >> and Kaiser. I personally like harris in this case -- we want to get a full > >> channel, two adjacent channels are usually not occupied, and as soon as we > >> pass the stopband frequency, we're basically at -100dB. > >> [2] assuming you want to use 2MS/s for your 2MHz wide band, 2MHz sampling > >> rate, and assuming 25kHz wide channels, 12.5kHz cut off frequency, 25kHz > >> start of stoppband. I get something like 440 taps. > >> [3] > >> https://gnuradio.org/doc/doxygen/classgr_1_1filter_1_1pfb__channelizer__ccf.html > >> > >> _______________________________________________ > >> 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 > >> > > > > > > > > -- > > GDB has a 'break' feature; why doesn't it have 'fix' too? > > > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
