SDRTrunk SDR newbie questions

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onyour9er

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Good morning!

If it’s not too much to ask, I have three questions in total. 1: Is there a more efficient way of listening to specific talk groups while scanning a p25 channel besides importing all the channels talk groups (there’s a lot) and muting all the unwanted ones? 2: While researching p25 scanning via SDR, many stated that 2 dongles were necessary to do so. After getting everything up and running, I don’t get how my second dongle is necessary in anyway for listening to the talk groups I’m interested in? Please advise. 3: I’m looking to transfer everything over to a Raspberry Pi 4 just to free up my computer and I was curious if the latest version of SDRtrunk is capable of running on such unit? If so, RPI 4 is offered in 1gb, 3gb, and 4gb ram variants, which would be most ideal for the software?

RTL V3 Dongles
SDRtrunk 0.5.0 Alpha 2
 

DSheirer

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1. Create an alias with a talkgroup range from 1-65,535 and set it to Mute. Create individual aliases for the talkgroups that you want to listen to. sdrtrunk will match specific talkgroups first and then talkgroup ranges.

2. In addition to decoding the control channel, sdrtrunk will create additional decoders for the traffic channels as talkgroup calls take place. You can use just 1 tuner if all of the channels 'fit' within the bandwidth of that tuner. Otherwise, you need additional tuner(s) to follow the traffic channels so that it can monitor the talkgroup calls.

3. The RPI4 is limited in CPU power and may not be sufficient to run sdrtrunk. Additionally, sdrtrunk needs a 64-bit operating system, unless you compile a 32-bit version yourself. I've read that they're readying a 64-bit version of Ubuntu for the RPI4 coincident with the new 8GB version, so it may be an option in the future.

Denny
 

boatbod

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3. The RPI4 is limited in CPU power and may not be sufficient to run sdrtrunk. Additionally, sdrtrunk needs a 64-bit operating system, unless you compile a 32-bit version yourself. I've read that they're readying a 64-bit version of Ubuntu for the RPI4 coincident with the new 8GB version, so it may be an option in the future.
As an alternative, op25 doesn't have as nice a gui as SDRTrunk but it will run on a RPi3 or RPi4
 

onyour9er

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1. Create an alias with a talkgroup range from 1-65,535 and set it to Mute. Create individual aliases for the talkgroups that you want to listen to. sdrtrunk will match specific talkgroups first and then talkgroup ranges.

2. In addition to decoding the control channel, sdrtrunk will create additional decoders for the traffic channels as talkgroup calls take place. You can use just 1 tuner if all of the channels 'fit' within the bandwidth of that tuner. Otherwise, you need additional tuner(s) to follow the traffic channels so that it can monitor the talkgroup calls.

3. The RPI4 is limited in CPU power and may not be sufficient to run sdrtrunk. Additionally, sdrtrunk needs a 64-bit operating system, unless you compile a 32-bit version yourself. I've read that they're readying a 64-bit version of Ubuntu for the RPI4 coincident with the new 8GB version, so it may be an option in the future.

Denny
Thanks for the reply, DSheier!

A little bit of confusion is setting in after attempting to do so. The counties p25 OASIS channel has just over 700 talk groups and out of those I would like to monitor around 10 or so. The way I tackled the issue of having a million transmissions coming in at once is I imported all the talk groups (over 700) within the channel and moved them into one alias. ALL of the talk groups in the alias I switched "listen" OFF and didn't give them any priority. For the 10 I wanted to listen to within' that alias, I switched "listen" ON and adjusted their priority to 1. It's successfully only producing audio for the talk groups I want but under the channels "EVENTS" its still receiving all of the other talk groups but just muted. Is this normal or is there a more efficient way of doing it where I can disable receiving all of the muted unwanted ones? It's safe to say the response above probably tells me how but I'm a little confused for the fact that I can only assign the channel one alias and I can only set a talk group range for one talk group at a time. Dumb it down for me?

As an alternative, op25 doesn't have as nice a gui as SDRTrunk but it will run on a RPi3 or RPi4
Thanks!
 

DSheirer

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It sounds like you have setup your alias list correctly. Where I said that you could use an alias with a talkgroup range to mute all of the other talkgroups, you've chosen to create individual aliases for each known talkgroup value and set each of those aliases to 'muted'. Either approach achieves the same result.

To clarify, you can only assign one alias list to the channel. You can assign as many aliases to that alias list as you want. Further, each alias can be aliased to as many discrete talkgroup values or talkgroup value ranges as you want.

sdrtrunk currently follows each and every call, regardless if you want to listen to the call or mute it.

There's an open issue to add a feature to designate a talkgroup as 'do not follow' which would prevent the call traffic channel from being decoded when the user doesn't want to listen to the talkgroup and doesn't want to record or stream the talkgroup.

Denny
 
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