4 ms·

Also, the US allows using UAT on 978 MHz for ADS-B requirement for planes below 18,000 ft. Most SDRs only decode 1090 MHz signal. It is possible to decode 978

Also, the US allows using UAT on 978 MHz for ADS-B requirement for planes below 18,000 ft. Most SDRs only decode 1090 MHz signal. It is possible to decode 978 MHz but requires more work to support both.

superkuh 7y ago
I know what you mean, you mean the software for SDRs is mostly geared towards tuning to 1090 MHz and decoding ADS-B pulses there. But to be clear: the SDR's tuners are rarely limited that way. Most can tune to 978 MHz even easier than 1090 MHz. Covering the entire VHF to UHF range is pretty typical.
- crankylinuxuser 7y ago
  When I've set up P25 receivers, it's common to use 2-4 RTL-SDR's to do the bulk of listening. Each rtl-sdr gets set with a different center freq, and the control channel tells when and where to listen. You can build a P25 listener for less than $100.
  - someguydave 7y ago
    which software do you use to demodulate P25? gnuradio?
    - crankylinuxuser 7y ago
      I use https://github.com/robotastic/trunk-recorder https://github.com/robotastic/trunk-recorder You'll use https://www.radioreference.com https://www.radioreference.com and get the appropriate control and voice channels for your area. You'll also get the talkgroups and put them in a CSV. From there, you'll use http://garvas.org/trunk-recorder/ http://garvas.org/trunk-recorder/ to determine how many RTL-SDR dongles (or others) you'll need, along with their respective center frequencies. Note that you'll copy/paste the relevant control/voice line for your p25 from radioreferece.com From there, just define where to store the files on the drive, and off it goes. There's a python webserver ( https://github.com/ScanOC/trunk-player https://github.com/ScanOC/trunk-player ) you can install for on-prem, and/or you can also upload it to openmhz website ( https://github.com/robotastic/trunk-recorder/wiki/Uploading-to-OpenMHz https://github.com/robotastic/trunk-recorder/wiki/Uploading-... ).
      - prashnts 7y ago
        Not OP, but thank you! I recently got a SDR dongle and was going to set it up. This will help.
zymhan 7y ago
Not difficult at all: https://www.adsbexchange.com/how-to-feed/adding-978-mhz-ads-b-capability-to-your-pipi2/ https://www.adsbexchange.com/how-to-feed/adding-978-mhz-ads-...

superkuh 7y ago

I know what you mean, you mean the software for SDRs is mostly geared towards tuning to 1090 MHz and decoding ADS-B pulses there. But to be clear: the SDR's tuners are rarely limited that way. Most can tune to 978 MHz even easier than 1090 MHz. Covering the entire VHF to UHF range is pretty typical.

crankylinuxuser 7y ago
When I've set up P25 receivers, it's common to use 2-4 RTL-SDR's to do the bulk of listening. Each rtl-sdr gets set with a different center freq, and the control channel tells when and where to listen. You can build a P25 listener for less than $100.
- someguydave 7y ago
  which software do you use to demodulate P25? gnuradio?
  - crankylinuxuser 7y ago
    I use https://github.com/robotastic/trunk-recorder https://github.com/robotastic/trunk-recorder You'll use https://www.radioreference.com https://www.radioreference.com and get the appropriate control and voice channels for your area. You'll also get the talkgroups and put them in a CSV. From there, you'll use http://garvas.org/trunk-recorder/ http://garvas.org/trunk-recorder/ to determine how many RTL-SDR dongles (or others) you'll need, along with their respective center frequencies. Note that you'll copy/paste the relevant control/voice line for your p25 from radioreferece.com From there, just define where to store the files on the drive, and off it goes. There's a python webserver ( https://github.com/ScanOC/trunk-player https://github.com/ScanOC/trunk-player ) you can install for on-prem, and/or you can also upload it to openmhz website ( https://github.com/robotastic/trunk-recorder/wiki/Uploading-to-OpenMHz https://github.com/robotastic/trunk-recorder/wiki/Uploading-... ).
    - prashnts 7y ago
      Not OP, but thank you! I recently got a SDR dongle and was going to set it up. This will help.

zymhan 7y ago

Not difficult at all: https://www.adsbexchange.com/how-to-feed/adding-978-mhz-ads-b-capability-to-your-pipi2/ https://www.adsbexchange.com/how-to-feed/adding-978-mhz-ads-...