SDRTrunk with 2 dongles. Doesn't appear to be using both dongles

[Roveer]

I have the latest SDRTRUNK running my local P25-1 system. I've got 2 dongles connected. It's receiving and playing traffic, but I was expecting the 2nd dongle to be tuned automatically with the first dongle being on the control channel. From what I've read this would all happen automatically.

From what I can see the 2nd dongle isn't doing anything even in times of multiple calls from that system. Is there some way I can verify that it is in fact doing something? Is there a configuration that I need to make?

Thanks,

Roveer

 

[GTR8000]

The second dongle will only be used if there is traffic outside of the bandwidth of the first dongle.

 

[Roveer]

The second dongle will only be used if there is traffic outside of the bandwidth of the first dongle.

My first dongle is set at 2.4mhz. Does this mean that I should intentionally lower this setting to force calls to be picked up my the 2nd dongle? If so, what mhz setting should I try? This is a 477 mhz system.

Roveer

 

[GTR8000]

Why would you want to force the second dongle to be used? If all traffic channels are within the 2.4 MHz bandwidth of one dongle, then all you need is one dongle.

You're listening to Morris County 4BA, correct? All of those channels are tightly spaced and will easily fit within a single dongle's bandwidth (1.2 MHz, actually). Find another use for the second dongle, you don't need it for Morris in SDRTrunk.

 

[AM909]

@GTR8000: Would it make sense to turn down the sampling rate to 1.6 MHz then?

 

[GTR8000]

@GTR8000: Would it make sense to turn down the sampling rate to 1.6 MHz then?

Not necessarily, no. If you turn it down too much, you run into the issue of rolloff at the outer edges of the spectrum. You're not going to gain any tangible advantage by reducing the sample rate below 2.4 MHz (technically 2.4 Msps), unless you're running on a PC with a weak CPU and low RAM. At which point you probably shouldn't be running such a resource hungry program like SDRTrunk to begin with.

If you start experiencing fade on traffic channels, then I suppose you could try reducing the sample rate of the dongle, but don't expect much (if any) improvement. The real improvement comes from reducing the amount of simultaneous transmissions being decoded, i.e. the Max Traffic Channels parameter in SDRTrunk.

 

[Roveer]

I had b den reading that this is preferred (one dongle for control channel, on for traffic). Had read that all that jumping around causes a single dongle to heat up. Yes, morris county 4ba. So if im going to use one dongle for this system I can use the 2nd for another system like state police or JCP&L? I am on an older laptop with 2gb

 

[AM909]

If the channels are spread over only 1.2 MHz, the dongle is never re-tuned (it doesn't need to "jump around"). It might be centered on 478.075, "hearing" +/- 1.2 MHz (or 960 kHz well) from there, which includes all the channels on that system, which ranges from 477.475 to 478.675. SDRTrunk runs separate threads that slice out and decode the individual channels from that 2.4-MHz-wide raw signal coming in from the dongle.

 

[GTR8000]

One dongle @ 2.4 Msps is all you need for Morris. The dongle is going to reach the same operating temperature regardless. You're likely going to have trouble decoding reliably with just 2 GB of RAM, and probably a fairly weak CPU. You'll have even more trouble when Morris dumps FDMA T-Band and moves to TDMA 700 MHz in a few months, as that is more resource intensive. I don't recall what the spread of their 700 MHz frequencies is off the top of my head, but you're going to need more than one dongle for that...and an upgraded PC to run it on.

Edit...I just looked at their SY licenses to refresh my memory. Spans from 769.28125 to 774.91875 with 8 channels spread out pretty widely in between. You'll likely need three dongles to cover it all.

 

[Roveer]

One dongle @ 2.4 Msps is all you need for Morris. The dongle is going to reach the same operating temperature regardless. You're likely going to have trouble decoding reliably with just 2 GB of RAM, and probably a fairly weak CPU. You'll have even more trouble when Morris dumps FDMA T-Band and moves to TDMA 700 MHz in a few months, as that is more resource intensive. I don't recall what the spread of their 700 MHz frequencies is off the top of my head, but you're going to need more than one dongle for that...and an upgraded PC to run it on.

Edit...I just looked at their SY licenses to refresh my memory. Spans from 769.28125 to 774.91875 with 8 channels spread out pretty widely in between. You'll likely need three dongles to cover it all.

So, for the time being I can run on one dongle and when this TDMA 700 come along I will likely need 3 dongles, correct?

Roveer

 

[GTR8000]

Correct.