Here....we......go

[ExploitedSanity]

With having been on furlough for a bit, I found myself drifting to the other categories on RR that I don't normally pay attention to. So here we are, down the SDR rabbit hole. I currently listen to the Euclid PD on the GCRCN simulcast network from a Whistler WS1040. As you probably already know, it doesn't handle simulcast the best. Knowing that I can't afford an SDS, I started leaning to the SDR route. After watching many vids and the like, I put an RTL-SDR Blog v4 (kit) in the Amazon cart. Figured I might as well get the kit that comes with the dipole. Due to me living in a 2nd floor apartment duplex, my choices are limited. I've only been using the stock antenna and a cheap wide band window antenna. I'm eyeballing one of the good mini discones ($70)? with great reviews. That will have to be after.

The system has 4 control channels. I have a feeling I know the answer to this but I have to ask anyways. Can I get away with one dongle? Will I hear both sides of the convo?

On the 1040, I just listen to Euclid PD on the GCRCN and Euclid FD on the MARCS system. I would definitely need 2 dongles for that, correct? I can only get 1 for now but i will know to get another when i can. I also like to listen to some of you guys/ladies on the GMRS freqs.

Thanks,
James

 

[Whiskey3JMC]

According to the SDR dongle calculator linked here you'd need 2 RTL dongles to cover the entirety of Cleveland Simul on GCRCN. One SDRPlay RSP should be able to do the job, albeit more costly than two RTL-SDRs

 

[ExploitedSanity]

According to the SDR dongle calculator linked here you'd need 2 RTL dongles to cover the entirety of Cleveland Simul on GCRCN. One SDRPlay RSP should be able to do the job, albeit more costly than two RTL-SDRs

Thank you for the response. 2 makes sense. I just wasn't 100% sure. Now what if I cut out listening to the FD on the MARCS system? Still 2?

 

[u2brent]

DSD+ has a mode that will follow traffic using 1 dongle. FWIW

 

[ExploitedSanity]

DSD+ has a mode that will follow traffic using 1 dongle. FWIW

I'm assuming you're talking with the fastlane? I saw that but wasn't sure if that was for me or not. I will definitely give that a shot though. I was thinking of starting with SDR++ as well for the malestrom I'm getting myself into. Seems to be heavily praised. Can't wait to see (hear) what's around me.

 

[n0esc]

Thank you for the response. 2 makes sense. I just wasn't 100% sure. Now what if I cut out listening to the FD on the MARCS system? Still 2?

When you see people talking about the number of dongles needed, that has to do with what frequencies they need to be able to "see" at the same time to cover a system. So when you look at that Cleveland system, you can look at the highest and lowest frequencies it uses, and subtract the two numbers to get the theoretical maximum amount of spectrum you need to see at one time. In this case it would be ~4.26MHz. Since the basic RTL-SRD chip works reliably at 2.4MHz, that's where the 2 comes in.

As far as what you want to listen to within that, the amount of traffic at one time, whether it is multiple talkgroups or one super busy one that takes up multiple radio channels at a time, that's dependent on the computer you have the dongles plugged into and it being powerful enough to handle that task. Most modern computers and laptops will do just fine. Another rabbit hole entirely if you haven't gotten there yet is running these SDR dongles on what are called single board computers like a Raspberry Pi or similar.

 

[Enforcer52]

To Cover all the freqs for Cuyahoga County on GCRCN would take 2 dongles. To cover the MARCS system would take an additional 2 dongles to cover all the freqs.

So a total of 4 to cover all the freqs that the PD and FD would possibly transmit on.

Dongle 1​

2.4MS/s (Covered Frequencies: 9)

Frequency (MHz)	Comment
769.041000000	Lowest Edge
769.256250000	Voice Channel
769.506250000	Voice Channel
769.756250000	Voice Channel
770.006250000	Voice Channel
770.156250000	Voice Channel
770.241000000	Center Frequency
770.431250000	Voice Channel
770.506250000	Voice Channel
770.781250000	Voice Channel
771.231250000	Voice Channel
771.441000000	Highest Edge

Dongle 2​

2.4MS/s (Covered Frequencies: 10)

Frequency (MHz)	Comment
772.516000000	Lowest Edge
772.656250000	Voice Channel
772.981250000	Voice Channel
773.293750000	Voice Channel
773.481250000	Voice Channel
773.716000000	Center Frequency
773.831250000	Control Channel
773.906250000	Voice Channel
774.156250000	Voice Channel
774.281250000	Control Channel
774.531250000	Control Channel
774.781250000	Control Channel
774.916000000	Highest Edge

Dongle 3​

2.4MS/s (Covered Frequencies: 10)

Frequency (MHz)	Comment
851.866000000	Lowest Edge
851.900000000	Voice Channel
852.150000000	Voice Channel
852.912500000	Voice Channel
852.962500000	Voice Channel
853.066000000	Center Frequency
853.200000000	Voice Channel
853.375000000	Voice Channel
853.712500000	Voice Channel
854.137500000	Voice Channel
854.187500000	Voice Channel
854.237500000	Voice Channel
854.266000000	Highest Edge

Dongle 4​

2.4MS/s (Covered Frequencies: 22)

Frequency (MHz)	Comment
854.047000000	Lowest Edge
854.337500000	Voice Channel
854.562500000	Voice Channel
854.612500000	Voice Channel
854.687500000	Voice Channel
854.712500000	Voice Channel
854.737500000	Voice Channel
854.837500000	Voice Channel
854.912500000	Voice Channel
854.962500000	Voice Channel
855.187500000	Voice Channel
855.247000000	Center Frequency
855.287500000	Voice Channel
855.337500000	Voice Channel
855.612500000	Voice Channel
855.662500000	Voice Channel
855.712500000	Voice Channel
855.737500000	Voice Channel
855.837500000	Voice Channel
855.887500000	Voice Channel
855.962500000	Control Channel
855.987500000	Control Channel
856.137500000	Control Channel
856.162500000	Control Channel
856.447000000

 

[ExploitedSanity]

Holy shnikies! Yeah, due to fundage, that will wait for a while. Hoping the furlough ends when it's supposed to. Anyways, at least in the meantime, I'll be able to explore and learn before dedicating dongles to that. That leads me to my next question. When using dongles with trunking software, does that prevent you from using the dongle for anything else while that's running?

 

[redbeard]

I'm assuming you're talking with the fastlane? I saw that but wasn't sure if that was for me or not. I will definitely give that a shot though. I was thinking of starting with SDR++ as well for the malestrom I'm getting myself into. Seems to be heavily praised. Can't wait to see (hear) what's around me.

DSD+ has it's own tuner so trying to use an extra app like SDR++ just adds extra work and points of failure. But the single dongle trunk following works well, basically the same thing a scanner does. Just use their included tuner with it, FMP.

And yes one app at a time per dongle.

 

[mtindor]

DSDPlus FastLane will trunktrack with one or two dongles / SDRPlays / Airspys. Why/how, when SDRTrunk requires multiple?

Well, DSDPlus Fastlane behaves like a scanner. One talkgroup can be heard / recorded at a time (generally). Just like a scanner.

With SDRTrunk, the idea is that you are capturing every conversation on the site (every active talkgroup on the site, even if there are 7 active conversations), which you can listen to, record, stream, etc.

Since SDRTrunk is meant to allow you to collect all audio from one or more sites (even on disparate systems), even when there may be 6-12 simultaneous talkgroups or more active on the site(s), it needs to be able to tune to every voice channel at the same time. That's why multiple dongles / SDRPlays / Airspys. SDRTrunk will require more system resources than DSDPlus because SDRTrunk is doing a whole lot more in the background.

 

[boatbod]

op25 can trunk with one dongle too.
Fundamentally, P25 passes signaling on both the control channel and voice channels, so no matter where the radio is tuned, it can keep and eye on all voice activity and retune if a higher priority call is identified.