Omitting APCO-P25 freq

[kc2klc]

I'm successfully using SDRTrunk on my Windows PC with an RTL-SDR to monitor our local emergency services, which use APCO-P25 Phase II. However, due to the RTL-SDR's 2 MHz bandwidth limitation, I only have 5 of the 6 utilized frequencies programmed in. The assigned frequencies are:
Ch. 1: 453.2750
Ch. 2: 453.4250
Ch. 3: 453.8375
Ch. 4: 454.3000
Ch. 5: 454.4750
Ch. 6: 460.2875
(Channel 3 is currently being used for control; that may eventually switch to channel 1).

I have several questions:
(1) Am I correct that I cannot include Channel 6 because it is outside the 2 MHz bandwidth of the other channels (unless I add a second RTL-SDR)?
(2) If that's the case, am I potentially missing much without it?
(3) When I eventually get SDRTrunk running on my Raspberry Pi, will I be able to copy over the default.xml file from my PC so that all the talkgroups I programmed in remain intact?

Thanks!

 

[maus92]

I'm successfully using SDRTrunk on my Windows PC with an RTL-SDR to monitor our local emergency services, which use APCO-P25 Phase II. However, due to the RTL-SDR's 2 MHz bandwidth limitation, I only have 5 of the 6 utilized frequencies programmed in. The assigned frequencies are:
Ch. 1: 453.2750
Ch. 2: 453.4250
Ch. 3: 453.8375
Ch. 4: 454.3000
Ch. 5: 454.4750
Ch. 6: 460.2875
(Channel 3 is currently being used for control; that may eventually switch to channel 1).

I have several questions:
(1) Am I correct that I cannot include Channel 6 because it is outside the 2 MHz bandwidth of the other channels (unless I add a second RTL-SDR)?
(2) If that's the case, am I potentially missing much without it?
(3) When I eventually get SDRTrunk running on my Raspberry Pi, will I be able to copy over the default.xml file from my PC so that all the talkgroups I programmed in remain intact?

Thanks!

I'm not sure what you mean "programmed in," as SDRTrunk only needs the active control channel entered to receive a system. Can you tell us what exact system that you are trying to monitor? A single Airspy R2 could cover the band width of this system, however you would need two RTL devices to cover both the 453-454 spectrum and the 460 frequency. I can't help you re: the Raspberry Pi however I doubt it has the horsepower to run SDRTrunk - OP25 Boatbod would be a better choice as it is lightweight in terms of system resource usage.

 

[kc2klc]

I am monitoring the Broome County NY public safety system. I was under the impression that I needed to add all the system frequencies to the "Source" section in the Playlist Editor (as indicated in the attached screen capture) - turns out I was mistaken. I deleted all but the control channel, and lo & behold, it still works fine!

I have an SDRPlay RSP1A which is unfortunately not supported in SDRTrunk; perhaps I can use it with OP25 - it can cover >4 MHz on my PC; not sure what bandwidth would be supported on the Raspberry Pi. (I really wanted a Pi with 4 GB RAM, but none were available for a long time; luckily I found the Pi with 2 GB RAM available locally through Craigslist.)

 

[maus92]

I would forget the sdrplay device - not widely supported. If you like SDRT, buy another $30 rtl type sdr to cover the 460 channel, or use op25 on the Raspberry Pi, and you can get away with using only one rtl device to cover all frequencies as op25 can retune the sdr.

 

[kc2klc]

Thanks to all for taking the time to respond. Sounds like the consensus is to use OP25, so that's what I'm going to attempt. If my measly 2 GB RAM is insufficient, I'll repurpose the Pi to other tasks (should be able to receive ADS-B & Inmarsat with it, which I currently do successfully with my PC).

 

[dave3825]

I am monitoring the Broome County NY public safety system. I was under the impression that I needed to add all the system frequencies to the "Source" section in the Playlist Editor (as indicated in the attached screen capture) - turns out I was mistaken. I deleted all but the control channel, and lo & behold, it still works fine!

Broome county public safety system? Do you mean the site Broome west simulcast site on the Central New York Interoperable Communications Consortium (CNYICC) system?

In any event, its best to have all the frequencies marked as control because if the one control you have changes you will not receive anything.

453.275c

453.425c

453.8375c

454.300c

 

[boatbod]

Thanks to all for taking the time to respond. Sounds like the consensus is to use OP25, so that's what I'm going to attempt. If my measly 2 GB RAM is insufficient, I'll repurpose the Pi to other tasks (should be able to receive ADS-B & Inmarsat with it, which I currently do successfully with my PC).

A single dongle op25 instance is entirely possible on a headless 2GB RPi.

 

[kc2klc]

Not sure what "headless" means - perhaps one that's remotely accessed? I'm using mine with keyboard, mouse & display connected.

 

[belvdr]

Not sure what "headless" means - perhaps one that's remotely accessed? I'm using mine with keyboard, mouse & display connected.

Headless = no keyboard, video, or mouse (i.e. KVM). Using the display uses more resources, so that may impact your performance.

 

[dave3825]

Not sure what "headless" means - perhaps one that's remotely accessed? I'm using mine with keyboard, mouse & display connected.

Headless, in this context, basically means that the computing device has no monitor or peripherals, such as a keyboard and mouse. Depending on the type of device they run in, headless systems may largely run autonomously or be remotely controlled. Servers in large data center environments are often headless.

 

[kc2klc]

I tried remotely accessing it from my Windows PC (based on a YouTube video and some online articles) but couldn't get Windows to see it (blank screen - no error). I'll probably have to make some further attempts (although I was hoping to use this setup portably).

 

[dave3825]

What exactly were you trying to access remotely? Sorry, only had 1 coffee.

 

[wilcom132]

I run mine on a headless Pi 4. When I need to, I access it remotely over my home network with VNC Viewer.

 

[kc2klc]

I attempted to access my Raspberry Pi remotely from my Win10 PC (both on the same home network) using VNC according to directions I found at www.raspberrypi.com/documentation/computers/remote-access.html and melgrubb.com/2016/12/11/rphs-v2-vnc/ (including uninstalling and reinstalling tightvncsdrver & xrdp), but Windows Remote Desktop just shows an empty window when attempting to connect to the Raspberry Pi (if I change parameters, I get an error instead of a blank window - so it seems like I'm halfway there). Caveat: I'm working off memory from a couple of months ago - I haven't gone back recently and verified some of the exact details of what I was experiencing.

 

[wilcom132]

I attempted to access my Raspberry Pi remotely from my Win10 PC (both on the same home network) using VNC according to directions I found at www.raspberrypi.com/documentation/computers/remote-access.html and melgrubb.com/2016/12/11/rphs-v2-vnc/ (including uninstalling and reinstalling tightvncsdrver & xrdp), but Windows Remote Desktop just shows an empty window when attempting to connect to the Raspberry Pi (if I change parameters, I get an error instead of a blank window - so it seems like I'm halfway there). Caveat: I'm working off memory from a couple of months ago - I haven't gone back recently and verified some of the exact details of what I was experiencing.

If you're using Raspbian (now called Raspberry Pi OS) on the PI, VNC is already installed and configured. You need to run the Raspberry Pi Configuration utility, go to the Interfaces section, and turn on VNC. Then, In Windows, download and install the free VNC Viewer app from RealVNC. Use VNC Viewer to connect to the PI, not Windows Remote Desktop. It's simple to set up and has worked on both my Pi 4 & Pi 3.

This is explained in both links in your post. I don't see any mention of xrdp in either article.

 

[kc2klc]

I'm still struggling to remotely access my Pi from my Windows PC. I'm following the instructions at Raspberry Pi Home Server v2: Remote Desktop (using VNC Viewer; not sure where I saw the instructions to use Windows Remote Desktop). I set a password & hostname in the Raspbery Pi Configuration, then used these credentials in VNC Viewer, but am receiving the error "Either the username was unrecognized, or the password was incorrect" (I am confident that I'm connecting to the proper IP address). Any idea what I'm missing?

 

[dave3825]

I have not done it recently but I never had a problem and the last time I had a problem it was the ip on the pi had changed.

 

[wilcom132]

I'm still struggling to remotely access my Pi from my Windows PC. I'm following the instructions at Raspberry Pi Home Server v2: Remote Desktop (using VNC Viewer; not sure where I saw the instructions to use Windows Remote Desktop). I set a password & hostname in the Raspbery Pi Configuration, then used these credentials in VNC Viewer, but am receiving the error "Either the username was unrecognized, or the password was incorrect" (I am confident that I'm connecting to the proper IP address). Any idea what I'm missing?

It sounds like you're connecting to the Pi but not entering the correct username and password. If you didn't change the default username and password when you installed the Pi operating system, then the default it uses is username = pi, password = raspberry. You say you set a password and hostname in the Raspberry Pi Configuration. The hostname is the name that identifies the pi on your network, not the username, so you may have just changed the password. Try username = pi and password = whatever you changed it to.

 

[kc2klc]

Thank you wilcom132 - that was the answer! I'm now headless