Why I won't be moving my feed to Broadcastify Calls

[bdp278]

So it’s telling me I need 5 dongles & 25 recorders. Is the recorder a software program? If I use SDRtrunk as my application, is that program a recorder. I pasted in the frequencies for the 1 site I wish to use, since it’s a simulcast site, pretty much all agencies in the New Orleans area go thru this site, and it’s the closest physical distance anyway to my office where I have my
setup.

770.70625a	772.69375	774.06875	774.38125	774.65625	774.84375	851.1625
				851.2125	851.2875	851.4625	851.5625	851.6875	851.9875	852.0375
				852.3625	852.575	852.7375	852.800	853.1625	853.275	853.375
				853.475a	853.600	853.675	853.750	853.850a	853.900c	854.6125
				858.6125

 

[dan-dekalb]

Recorders represent resources allocated to decoding voice traffic within that 2MHz of spectrum that RTL-SDR is monitoring. It's largely a target to those like me using the Linux application "trunk-recorder" where we can drop in the values that come back from that site. Do you know if that site is using P25 Phase 2? As I understand, OP25 and trunk-recorder (which is based on OP25 libraries) can decode phase 2.

I'm running 5 dongles on the Raspberry PI 4, but I only need about 12 recorders plus one analog conventional recorder. I suspect 25 would overwhelm the PI's resources. Assuming you don't need Phase 2, SDRtrunk on a reasonably fast PC should work. I personally have no experience with it, so I'm going off what I've read.

There is a long but through write-up at DSheirer/sdrtrunk showing how to set up SDRtrunk. I'd start there. One thing to be aware of is signal strength seems to be much more critical with the RTL-SDR than an conventional scanner. I'm about 2 miles away from one system that I monitor and it locks in no problem. I'm about 7 miles away and sometimes have issues with decoding.

Be aware that since you're capturing everything, it is possible for your conventional feed to become backlogged if the system is very busy. You may have to trim what you stream or split it into two or more streams. The calls platform uses an "ingest" interface where as soon as the individual call is complete, it is streamed individually to Broadcastify. Then listeners to the Calls platform can create their own choice of talk-groups to listen to.

Hope this helps.

Dan

 

[bdp278]

Thanks very much for your answers, I'm finally getting a better understanding of SDS. To answer your question, the system here is P25 Phase 1, and I will NOT be running all agencies, as all of the law enforcement & some EMS are now encrypted, no sense in including those in the list. Mainly the 18 or so FD's (with each FD using 1-3 TG's, & 1 FD (New Orleans) using about 15 TG's) that all run thru the site I sent over previously, plus one conventional frequency 855.075 for 1 small FD that refuses to migrate onto the P25 system. I understand there are dongles such as airspy that cover a wider range of 5MH, are those any better? Also I keep seeing Raspberry PI come up, what is that, and do I need that device if I'm using a Windows 10 PC? Where does the usb hub with all the dongles connect to? Does the SDRtruck application replace the recorders, or are the recorders a separate software install? I'm just trying to get a handle on what hardware & software I'll need to make this all work. Many Thanks again for your time.

 

[dan-dekalb]

Raspberry PI is a small inexpensive single-board computer normally running a stripped down version of Linux. If you don't have any experience in Linux, I would recommend staying on the Windows side to get started. In the case of TrunkRecorder, you define the number of recorders needed for each dongle and TrunkRecorder starts a recorder process to make sure it has resources when a transmission comes in. I'm assuming SDRtrunk does something similar.

Below is a picture of my layout. I'm using an Anker 10 port USB 3.0 hub. (https://smile.amazon.com/gp/product/B005NGQWL2/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1) The dongles get very hot in operation, and they are thick enough that they won't fit in the standard spacing of a USB hub. This has given me reliable operation and reasonable thermal stability. The white box in the picture is my Raspberry PI. In your case, you'd want to plug the hub into a USB 3.0 port on your windows PC. I originally tried running a single antenna with an amplifier and notch filters to feed all 4 dongles. What I found was that I was apparently overloading dongles for the system close to me or I wasn't getting enough signal for the distant system. I switched to two separate antennas, a lower gain for the close system (2 & 3 from the left) and a bit higher gain for the distant system (4 & 5). The dongle on the left goes to it's own dedicated VHF antenna for the conventional system I monitor.

You might want to start out with a single RTL-SDR it like https://smile.amazon.com/RTL-SDR-Bl...qid=1599230360&sprefix=RTL-SDR,aps,162&sr=8-3 to get started. Plug a single dongle into your computer, fire up SDRTrunk and play with it before going the while 5-dongle route.

 

[BenFranske]

I understand there are dongles such as airspy that cover a wider range of 5MH, are those any better?

Only in that you can cover more bandwidth with fewer dongles. However, the RTL-SDR dongles are much less expensive so in the end I think the consensus is pretty much to just stick with more of the RTL-SDR dongles unless you have some edge case that makes fewer dongles more important. Be sure to get the TXCO (temperature compensated oscillator) ones.

I've used both SDRTrunk and trunk-recorder. SDRTrunk is very user friendly and easy to get up and running as it does a lot of work for you like calculating the error offset of your tuners and automatically can create traditional Broadcastify streams as well as upload to Calls. It also has a GUI which allows for easier setup. However, I also had issues with it crashing about every 24 hours so I had to put a restart timer on it when I was using it. I'd say it's great for local listening periodically and for a proof of concept system to see what you can cover but if you're going to run long term you will probably want to switch to Linux and trunk-recorder.