SDR# Picking up local frequencies?

[jcroy]

Wasn't sure how to title this.

I bought a rtlsdr using the dipole antenna and can use it to listen to fm radios and unencrypted radio frequencies in a large city.

I'm in a new area that uses a digital system (RI) and struggling to find some digital frequencies. Does anyone have any pointers or tips? I'm new to sdr and radios stuff.

I'm struggling to see if my lack of sound is due to lack of transmissions or due to poor receiver positioning. Is there a website that tracks active vs non active times so I can figure out when is a good time to tune in? It's for a personal coding project as opposed to content.

 

[morfis]

Country would be a hude help. For America then the databases here on radioreference would be a good starting point.
For other countries local scanner bulletin boards or official systems (such as the UK WTR...though that should only be regarded as a rough guide).
use the rtl device as a scanner and search the spectrum for active frequencies...look at the active ones to see what kind of traffic is on them - loads of websites, such as Signal Identification Wiki - to help you identify the digital modulation waveforms.

With more information people more local to you might be able to offer more targetted guidance.

 

[Markb]

Seeing the "(RI)" in your post, I am assuming this is the system you are trying to monitor:

Rhode Island Statewide Communications Network (RISCON) Trunking System, Statewide, Rhode Island

Rhode Island Statewide Communications Network (RISCON) Trunking System Profile

www.radioreference.com

Try tuning in the blue and/or red frequencies and see if you can hear the control channel. Also adjust the gain and see if that makes a difference.
Do you have any digital decoding software set up? If not, all you're going to hear is noise.....

 

[sonm10]

I would use DSD+ or SdrTrunk for the Rhode Island system

 

[Carter911]

I, also, am a newbie, but I'll share a few thoughts.

Check out the RTL-SDR.com website as one starting point.
It has a "Quick Start" guide tab, and a (lengthy) list of software and the platforms they run on, (Win, Linux, Mac, etc.).

Hopefully you purchased an RTL-SDR WITH a temperature compensated oscillator.
That is essentially a must for listening to an 860-ish MHz APCO-25 (Phase I) system, (e.g. RISCON).

Google OP25 for info on one of the software options for using the RTL-SDR to listen to the system.
There is the original OP25 version and the Boatbod version of OP25.
I am using the Boatbod version on an Raspberry Pi ( RPi 3B+ ) to monitor Ohio's system and it is working well.

In short, you need the software to monitor the control channel, which says which "Talk Groups" are currently talking, and on which frequency. The software then tunes to the correct frequency for that transmission, reconstructs the audio data from the digitally transmitted packets, and then runs the voice data through another layer of decoding, (not De-crypting), to finally hear the audio.

There are numerous You-Tube videos on setting up OP25, look at SEVERAL of them to find one that makes sense to you.

The "tricky", (actually frustrating as hell), part of the process is fine tuning the SDR dongle to center it on the control channel frequency.
This is essentially a trial and error process, adjusting the -q XYZ parameter until one sees the Talk Groups on the display.
In the BoatBod version, there is also a -d XYZ fine tuning option, and one can use the , . < and > keys to tune the system, while watching for the Talk Groups to show up, and then watching the "eye pattern", ( "4" key to pop this graph up), so that the pattern is transitioning at +/- 3.

You will have to confirm that the Rhode Island, (USA), RISCON system is what you would like to monitor, and what computer platform you intend to use, and you will likely get more guidance.

Good luck, have fun!

JC

 

[Markb]

Also, I would be highly suspect of an antenna that was included in an RTLSDR package. Generally they are junk.

My suggestion would be to ditch SDR# for digital monitoring and use the FMP24 application that's included with DSDPlus.