OP25 OP25 multiple frequencies

lazymichael

Newbie
Joined
Apr 19, 2023
Messages
4
Hey all!

I was hoping you all could help me I am wondering if it is possible for op25 to listen to three frequencies only one is conventional p25. The three frequencies I want to listen to are all really close together not sure if that matters or not. I am thinking this can be done using multi_rx and cfg.json but I am not sure what all do change in the cfg.json file. Any help would be appreciated.

I have already got op25 running on an old laptop and it is working just fine with the conventional p25.
 

wgbecks

Active Member
Joined
Jan 17, 2005
Messages
903
Location
NE Wisconsin
You didn't specify frequencies or modes in your post other than to state one is conventional P25. The three frequencies and modes
would fist need to be defined to facilitate further discussion.

However, with some caveats, multi_rx.py can be configured with multiple receivers sharing a single SDR. One caveat being the frequencies
of the three receivers must fall withing the usable bandwidth of a given single SDR and the other consideration is how you desire use the
audio derived from the three receivers.

For example, it's possible to stream the three audio sources independently or that you can opt to combine them into a single composite
output using Liquidsoap with op25.
 

lazymichael

Newbie
Joined
Apr 19, 2023
Messages
4
The three frequencies are 154.400, 155.070 and 155.235. 155.070 is the only one that is P25 the others are FMN. I want the audio to be output to the speaker I have hooked up to the laptop.

Sorry I am very new to all this still trying to learn everything. Having lots of fun though!

Here is the link to my counties frequencies if it helps at all. link
 

wgbecks

Active Member
Joined
Jan 17, 2005
Messages
903
Location
NE Wisconsin
This seems doable with Boatbod multi_rx.py in that the receiver(s) can be configured for analog (FM) operation. Would I be correct to
assume that all three of the frequencies (stations) are repeaters that would provide a rather stable signal at your receiving location?

OP25 runs on various modules or blocks in GNU Radio that includes the demodulation of FM signals but the squelch blocks leave a lot
to be desired as they are signal level driven as opposed to being noise operated as conventional FM receivers employ. Still, this works
very well where signal levels are fairly stable as would be the case where dispatch and all units are retransmitted through a repeater.

Unlike a scanner, all receives configured in multi_rx.py will be live at all times that undoubtably will result at times in simultaneous audio
emanating from two or possibly all three of the channels when processed to a single speaker output. Optionally, additional audio
hardware could be added and configured to facilitate independent audio channels.

What hardware platform did you have in mind to run Linux and op25 on?
 
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