Will the RTL-SDR work for digital frequencies?

Main forum to discuss RTL-SDR related topics.
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Jarwolf
Posts: 2
Joined: Wed Apr 04, 2018 1:02 pm

Will the RTL-SDR work for digital frequencies?

Post by Jarwolf » Wed Apr 04, 2018 1:07 pm

Hello. I am jumping in deep water here. I am wanting to get into radio's and whatnot. Next Tuesday, I am going to take my first Technician exam ever. I hope I end up passing it! Anyhow, I am attending college for Cyber Security and Network Systems and I stumbled across a Software Defined Radio that involves computers. AWESOME!!!!! My question is; would this RTL-SDR work for DIGITAL frequencies? My local PD, FMD, EMS switched to digital. I just don't got the $200 + to spend on a scanner...

snn47
Posts: 92
Joined: Tue Dec 27, 2016 11:00 pm

Re: Will the RTL-SDR work for digital frequencies?

Post by snn47 » Wed Apr 04, 2018 3:20 pm

There are no digital or analogue Frequencies. Frequencies are often calle "analogue or digital" frequencies, because they are used for transmission of either analogue or digital modulations.

A SDR can receive any modulations that is within the tuning/frequency range that they can tune to. The SDR bandwidth/dynamic range is more limited by the A/D-converter used. For the cheaper SDR-USB sticks the bandwidth is about 1.8 MHz, more expensive SDR can achive 10 to 100 MHz. You can find all the information on this webpage and in the forum.

So if the signals you are interested in fall within the tuning/frequency range, the bandwidth/dynamic range that the SDR you choose it can in principle decode them if the reception of the modulation is supported by a program.

Kenn
Posts: 40
Joined: Fri Apr 08, 2016 8:43 pm

Re: Will the RTL-SDR work for digital frequencies?

Post by Kenn » Thu Apr 05, 2018 7:49 am

In short, yes, with a few caveats. Public Service communications in the US that have gone digital typically use the APCO/P25 system, usually in the 800's-900's MHz. (You can check www.radioreference.com to confirm that for your area).

The RTL can receive in those frequency ranges easily enough, the thing you'll need to do is configure software to follow trunked calls and decode the digital transmission into an audio stream. There's guides on this site covering how to do that depending what platform you're on. Some will not do phase II of the APCO/P25 standard.

Dedicated hardware scanners tend to work better at clearly & reliably monitoring these systems, but they do come at a price.

Congrats on going for your tech license and diving in. You cannot go wrong with knowledge and all this stuff will only become more relevant as time passes.


-Ken

https://ranous.wordpress.com

:mrgreen:

Jarwolf
Posts: 2
Joined: Wed Apr 04, 2018 1:02 pm

Re: Will the RTL-SDR work for digital frequencies?

Post by Jarwolf » Thu Apr 05, 2018 4:10 pm

Thank you guys for the information! It is all gibberish to me however, I am trying my best to understand. I guess OH changed their signal to "statewide MARCS 800/700 trunked radio system" whatever that means! haha.

frogdog
Posts: 1
Joined: Fri Apr 06, 2018 1:38 am

Re: Will the RTL-SDR work for digital frequencies?

Post by frogdog » Fri Apr 06, 2018 1:42 am

Hi
Yes, Run well on Ubuntu 16.4 with Gqrx (easy to download and install) for radio which worked very well. I then downloaded Kaffeine and l was able to watch all the local digital TV and associated radio channels. I found Kaffeine easy to use, clicked scan, Highlighted scan results and clicked "add selected". To play select channel abd click play. I did not have to read any help files.
I tried VLC and with help from the internet got it working. I used Kaffeine to find the Channel frequency's and had to change the bandwidth from auto to 7Mhz. Open Vlc, -- click media-open capture device, select digital TV in the drop down menu. It should show "/dev/dvb/adapter0" for the tuner card or similar. Type the multiplex frequency. eg 184625 khz for Australia channel 7. Change bandwidth from automatic to 7 Mhz in the drop-down menu. Press play. It will open the main channel, to watch sub channels click playback, then program and chose from the drop-down menu. I found while the quality seemed better with VLC it had a habit of displaying a blank screen after several channel changes and had o close VLC or reboot to correct.
Gerald

w5dxp
Posts: 17
Joined: Sat Apr 14, 2018 9:05 pm

Re: Will the RTL-SDR work for digital frequencies?

Post by w5dxp » Sat Apr 14, 2018 9:23 pm

Jarwolf is an amateur radio operator as am I. The answer to the original question is, yes, and I am doing it. What I have is a $21 RTL-SDR V3 and a $49 SpyVerter up-converter which I run with SDR# (SDR sharp) free software. That covers AM, FM, and SSB. For the digital modes, I pipe the audio output from SDR# to FLDigi (also free) and FLDigi decodes most of the digital modes available to amateur radio operators, e.g. PSK, Olivia, TTY, etc. The exceptions are the JTnn and FT8 modes which I don't use.

https://www.rtl-sdr.com/ and http://www.w1hkj.com/ for FLDigi.

w5dxp
Posts: 17
Joined: Sat Apr 14, 2018 9:05 pm

Re: Will the RTL-SDR work for digital frequencies?

Post by w5dxp » Mon Apr 16, 2018 11:51 am

I might add that the RTL-SDR V3 dongle will work for HF without the up-converter if direct sampling is selected (in SDR#) but the SpyVerter R2 up-converter has some additional frequency filtering that I find to be worth the $50 cost:
RF Filtering: Low Pass Filter with corner at 65 MHz – 75dB ultimate rejection
IF Filtering: Band Pass Filter with corners at 120 MHz and 180 MHz – 75dB ultimate rejection

W1ABA
Posts: 21
Joined: Fri Jul 06, 2018 5:05 pm

Re: Will the RTL-SDR work for digital frequencies?

Post by W1ABA » Fri Jul 06, 2018 8:27 pm

W5DXP hit the nail dead center, kudos!

Heed his words.

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