OK, Here it is... at least, a beta version. I have yet to come up with
a concise explanation of the channel map and why you'd want to
oversample, but it is functional.
This flowgraph would work equally well by directly connecting all the
ports together, but I'm a big fan of using virtual sources and sinks to
make the design somewhat self-documenting..
On Sat, Aug 1, 2015 at 4:55 AM, Markus Heller <address@hidden
<mailto:address@hidden>> wrote:
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
<address@hidden <mailto:address@hidden>> 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, <address@hidden
<mailto:address@hidden>> 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 <tel:21.07.2015%2019>: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
> >> address@hidden <mailto:address@hidden>
> >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> >>
> >>
> >> _______________________________________________
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> >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> >>
> >
> >
> >
> > --
> > GDB has a 'break' feature; why doesn't it have 'fix' too?
>
>
>
--
GDB has a 'break' feature; why doesn't it have 'fix' too?
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