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Re: [Discuss-gnuradio] isolate channels from wideband
From: |
Chris Kuethe |
Subject: |
Re: [Discuss-gnuradio] isolate channels from wideband |
Date: |
Sun, 2 Aug 2015 11:39:17 -0700 |
Yes, I saw that, and have not yet had time to look at it. I went with
NOAA weather radio because it's always on and I can see a few of the
frequencies which makes it a great test source ... my local hams
aren't always as predictable, but channelizing your local repeaters
would be a very fine use of a PFB
On Sun, Aug 2, 2015 at 11:32 AM, Tim K <address@hidden> wrote:
> Just as a heads up, someone mailed this into the mailing list the other day.
> I think it accomplishes exactly what you all want -- although it doesn't use
> PFBs as I recall.
>
> https://github.com/madengr/ham2mon
>
> - Tim
>
> On Sun, Aug 2, 2015 at 2:18 PM, John Ackermann N8UR <address@hidden> wrote:
>>
>> Hi Chris --
>>
>> Using the variables, I now have the program working in general.
>>
>> The channel mapping gave me some nightmares, though. I finally decided
>> that you need two maps -- one for the channelizer block, where you do the
>> 4,5,6,7,0,1,2,3 translation, and another for the GUI that is a simple 0..7.
>>
>> With that, it seems to be working well although my WBX front end seems to
>> have been fried as it is more deaf than it used to be. Time to switch to
>> hardware troubleshooting mode...
>>
>> Thanks, again!
>>
>> John
>> ----
>>
>>
>> On 08/02/2015 12:10 AM, Chris Kuethe wrote:
>>>
>>> Thanks for pointing out the paste-o. I'll fix that.
>>>
>>> I'm using gnuradio 3.7.8rc1, which has helper blocks for computing
>>> filter taps. You can replace them with variables:
>>>
>>> pfb_taps = firdes.low_pass(2.0, oversampled_width, noaa_fm_dev * 2,
>>> 2500, firdes.WIN_HAMMING, 6.76)
>>> lpf_taps = firdes.low_pass(1.0, hardware_rate, noaa_band_width / 2,
>>> noaa_chan_width, firdes.WIN_HAMMING, 6.76)
>>>
>>> On Sat, Aug 1, 2015 at 5:00 PM, John Ackermann N8UR <address@hidden>
>>> wrote:
>>>>
>>>> Thanks much for this, Chris! I look forward to playing with it, but...
>>>>
>>>> When I load the flowgraph on my GRC 3.7.6.1 system, I get a "Missing
>>>> Block"
>>>> error for each of lpf_taps and pbf_taps, triggering errors in the xfft
>>>> and
>>>> channelizer blocks.
>>>>
>>>> I also had an error in the "Multiply Const" block coming out of channel
>>>> 7.
>>>> but that was caused by a missing space before "else" in the evaluation.
>>>>
>>>> Help?
>>>>
>>>> But thanks so much for taking this on. It's the perfect starting point
>>>> for
>>>> some projects I've been wanting to work on!
>>>>
>>>> John
>>>> ----
>>>>
>>>> On 08/01/2015 03:26 PM, Chris Kuethe wrote:
>>>>>
>>>>>
>>>>> 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
>>>>> > >>
>>>>> > >>
>>>>> > >> _______________________________________________
>>>>> > >> Discuss-gnuradio mailing list
>>>>> > >> address@hidden <mailto:address@hidden>
>>>>> > >> 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?
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Discuss-gnuradio mailing list
>>>>> address@hidden
>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>>>
>>>>
>>>> _______________________________________________
>>>> Discuss-gnuradio mailing list
>>>> address@hidden
>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>
>>>
>>>
>>>
>>
>> _______________________________________________
>> Discuss-gnuradio mailing list
>> address@hidden
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>
--
GDB has a 'break' feature; why doesn't it have 'fix' too?
- Re: [Discuss-gnuradio] isolate channels from wideband, Markus Heller, 2015/08/01
- Re: [Discuss-gnuradio] isolate channels from wideband, Chris Kuethe, 2015/08/01
- Re: [Discuss-gnuradio] isolate channels from wideband, John Ackermann N8UR, 2015/08/01
- Re: [Discuss-gnuradio] isolate channels from wideband, John Ackermann N8UR, 2015/08/02
- Re: [Discuss-gnuradio] isolate channels from wideband, Chris Kuethe, 2015/08/02
- Re: [Discuss-gnuradio] isolate channels from wideband, John Ackermann N8UR, 2015/08/02