SDRTrunk Can SDRtrunk monitor multiple trunk sites?

[AB5ID]

Can SDRtrunk monitor multiple trunk sites and if so, how does it do it?
I currently use OP25 to monitor 3 separate sites with one dongle. OP25 switches from site to site (3 control channels) until there is voice traffic, after there is no more traffic, the site to site switching resumes.

 

[GTR8000]

SDRTrunk does not "scan" control channels; it locks onto the control channel and remains locked on it indefinitely. SDRTrunk does not leave the control channel to tune to traffic channels; it requires all control and traffic channels to be within the bandwidth of the dongle(s) available to the software.

That means two things:

1. If using only one dongle, all voice traffic channels must be within the bandwidth of the dongle, taking into account the control channel. That equates to ~2.4 MHz chunk of spectrum for RTL dongles, ~6 MHz for AirSpy Mini, ~10 MHz for AirSpy. If the range of all channels at a site exceeds the dongle's coverage, you will need multiple dongles.

2. If you wish to track multiple sites, the same rule as #1 applies with regard to those control and traffic channels. They must all be within the bandwidth of the dongle, otherwise you will need multiple dongles.

 

[AB5ID]

2. If you wish to track multiple sites, the same rule as #1 applies with regard to those control and traffic channels. They must all be within the bandwidth of the dongle, otherwise you will need multiple dongles.

Thanks for the reply. If I use RTL dongles it looks like I should use at least one dongle per site on the control channel and additional dongle(s) for traffic? Any idea of how much RAM and what type of processor it would take to monitor 3 sites with 4 dongles?

 

[GTR8000]

It depends on how many dongles you need, and how busy each site is. If you are decoding TDMA traffic, that might require a bit more horsepower over FDMA traffic.

What three specific sites are you wanting to decode? SDRTrunk will use the entire available bandwidth of the dongle(s) to maximize efficient usage of each, so if everything you want to monitor falls within a few MHz of contiguous spectrum, you may only need two or three dongles in total.

So for example if everything you'll be monitoring falls within the NPSPAC channels of 851-854, you would only need two dongles to cover that 3 MHz of spectrum, with some overlap. If you want to monitor a 700 MHz site, you have to determine what frequencies are in use, as that band spans 769-775 and you could wind up needing three dongles to cover the whole 6 MHz of spectrum. Same with 800 MHz, which spans 851-860 (854-860 is mixed public safety, business/industrial, and SMR), potentially requiring four dongles to cover it all.

 

[AB5ID]

What three specific sites are you wanting to decode? SDRtrunk will use the entire available bandwidth of the dongle(s) to maximize efficient usage of each, so if everything you want to monitor falls within a few MHz of contiguous spectrum, you may only need two or three dongles in total.

The three sites are MO East Jackson County Site, MO Kansas City Site, and Lee's Summit Site. Two of the sites are P25 Phase1 and one is P25 Phase2, the Kansas City site is very active. I use OP25 to listen to all 3 sites with one dongle rolling from site to site. Always wanting to tinker, I am curious about what SDRtrunk has to offer, how many dongles I would need, and what kind of computer (processor/RAM) would be recommended?

 

[GTR8000]

So essentially you need to cover 851 to 861 MHz and everything in between, as the lowest frequency is 851.050 for the KC site, and the highest frequency is 860.7875 at Lee's Summit. That works out to 9.7375 MHz worth of spectrum, which can probably be done using 4 RTL dongles set at a sample rate of 2.56 MHz each. A single AirSpy may also provide the required coverage, but of course is a pricier option vs 4-5 $20-25 TCXO RTL dongles. The biggest hassle with multiple dongles is the antenna situation, and perhaps needing a USB hub to handle all of them.

Of course the upside is that all three sites would be monitored concurrently, and so you're certainly going to get a lot more activity than if the software was rolling through each site one at a time.

As for the PC, the more powerful the better. You want a fairly modern and decently powerful CPU, probably nothing less than a quad core i5 or i7 (or AMD Ryzen equivalent), with an absolute minimum of 8 GB of RAM, 16 GB being recommended.

 

[mtindor]

So essentially you need to cover 851 to 861 MHz and everything in between, as the lowest frequency is 851.050 for the KC site, and the highest frequency is 860.7875 at Lee's Summit. That works out to 9.7375 MHz worth of spectrum, which can probably be done using 4 RTL dongles set at a sample rate of 2.56 MHz each. A single AirSpy may also provide the required coverage, but of course is a pricier option vs 4-5 $20-25 TCXO RTL dongles. The biggest hassle with multiple dongles is the antenna situation, and perhaps needing a USB hub to handle all of them.

Of course the upside is that all three sites would be monitored concurrently, and so you're certainly going to get a lot more activity than if the software was rolling through each site one at a time.

As for the PC, the more powerful the better. You want a fairly modern and decently powerful CPU, probably nothing less than a quad core i5 or i7 (or AMD Ryzen equivalent), with an absolute minimum of 8 GB of RAM, 16 GB being recommended.

They Airspys are going to give you less than 10 / 6 msps -- I think somewhere between 8 and 9 MHz of coverage for the Airspy R2 and around 5 MHz with the Airspy mini. I know that you don't have the full 10/6 in SDRSharp, and I know that when I tried to use an AIrspy R2 on a system with channels spread out about 9.5 Mhz, some channels would be out of range.

And depending upon what you are running the Airspy (R2 at least) on, you might run into significantly higher CPU usage than you would with using 4 dongles at 2.5 sample rate. At least that is my experience, running an Airspy R2 on an Odroid N2 versus running a bunch of dongles to provide same coverage. Not sure if the same applies for any LInux box or for SDRTRunk and Windows.

Mike