Narrow Band / Wideband

Here is where you can get help with using and setting up POCSAG and related topics
KE7FNS
Pi-Star Team
Posts: 2429
Joined: Wed Apr 17, 2019 11:11 pm

Re: Narrow Band / Wideband

Post by KE7FNS » Fri Dec 03, 2021 4:12 am

kd5hnm wrote:
Fri Dec 03, 2021 2:56 am
I need to adjust the shift to ±2.5 kHz because my pagers are locked on Narrowband and my pps software doesn't let me change that option, is there an adjustment for adjusting the frequency shift?
I've already told you there is NOT a way to change between narrowband and wideband, it is hardcoded at whatever it currently is.

At the minimum the MMDVM_HS firmware would need to have that added or at least a custom firmware compiled to enforce narrowband. I'm sure its as easy as changing a single 0 to a 1 and recompiling, but I don't quite understand how those registers work or if they are big endian or little endian or what. It also doesn't help that I don't have any pager hardware so that makes it very difficult to test anything.

If you wanted to make it a selectable option then you'd also have to have that feature added to MMDVMHost, and add the messaging structure to communicate with the STM32 to switch between the bandwidths.

Then once that all happens THEN the option can be added to the Pi-Star dashboard.

Its not an easy/simple process.
If someones previous actions are any indication of their future actions, then I predict the deletion and removal of access will happen at any moment. 7-11-2020.

"07/13/20 This Website Has Been Taken Down" ... again :lol: and again

kd5hnm
Posts: 6
Joined: Wed Dec 01, 2021 2:41 am

Re: Narrow Band / Wideband

Post by kd5hnm » Fri Dec 03, 2021 4:32 am

I completely understand what you are saying... Didn't know if there was some simple terminal command or something off the ui.

Didn't want you guys to reinvent the wheel.. I'll look for another route for my project...

This just knocks out a lot of surplus pagers in a market that is already very limited.. I don't understand why the pager manufactures won't allow that selection to be changed.

Thanks for your time..

73's

KD5HNM

KE7FNS
Pi-Star Team
Posts: 2429
Joined: Wed Apr 17, 2019 11:11 pm

Re: Narrow Band / Wideband

Post by KE7FNS » Fri Dec 03, 2021 6:04 am

kd5hnm wrote:
Fri Dec 03, 2021 4:32 am
I completely understand what you are saying... Didn't know if there was some simple terminal command or something off the ui.

Didn't want you guys to reinvent the wheel.. I'll look for another route for my project...
I'm pretty sure its doable. Being bored and curious is a dangerous combination. I looked at the code and the datasheet and even though I'm still a bit confused, I believe it is possible. Its no where near a parameter in the software, but it should be possible to lock the bandwidth for all pocsag at a lower value.

Its currently hardcoded at "Dev: 4500 Hz, symb rate = 1200"

Tomorrow I'll sit down and see if I can actually change the bandwidth. Now that I think about it I don't need a pager, I can just use a SDR and see the bandwidth.
If someones previous actions are any indication of their future actions, then I predict the deletion and removal of access will happen at any moment. 7-11-2020.

"07/13/20 This Website Has Been Taken Down" ... again :lol: and again

kd5hnm
Posts: 6
Joined: Wed Dec 01, 2021 2:41 am

Re: Narrow Band / Wideband

Post by kd5hnm » Fri Dec 03, 2021 2:56 pm

Thanks for your work on such a great software!

It's really appreciated...


Thanks so much for looking into it. Just a suggestion that will open up the pocsac functions to many more pager units...


73's

KD5HNM

KE7FNS
Pi-Star Team
Posts: 2429
Joined: Wed Apr 17, 2019 11:11 pm

Re: Narrow Band / Wideband

Post by KE7FNS » Fri Dec 03, 2021 10:08 pm

kd5hnm wrote:
Fri Dec 03, 2021 2:56 pm
It's really appreciated...
I'm not convinced the issue is narrowband vs wideband.

I've modified the firmware to what I believe to be narrow band, and it doesn't appear to make any difference. The signal is identical to what it is when it is set to wideband.

It is contained within a 12.5Khz bandwidth grey area as you can clearly see in the attached image.
pocsag.jpg
pocsag.jpg (130.71 KiB) Viewed 433 times
According to Andy your Unification Alpha + uses Motorola Flex, and not pocsag, so that pager isn't compatible.
If someones previous actions are any indication of their future actions, then I predict the deletion and removal of access will happen at any moment. 7-11-2020.

"07/13/20 This Website Has Been Taken Down" ... again :lol: and again

kd5hnm
Posts: 6
Joined: Wed Dec 01, 2021 2:41 am

Re: Narrow Band / Wideband

Post by kd5hnm » Fri Dec 03, 2021 10:20 pm

My pagers are pocsag..

Not sure about the wide band issue.. I tried with my visoplex pocsag encoder, set to 1200 baud, mode 2, and the pagers work just fine. Not sure what the mode selection is in the visiplex, Not much info on it.. I think that transmitter will let me switch from narrow to wide, so I'll try with the pagers set to narrow and the transmitter set to wide, and see if I can reproduce the scrambled text I'm getting from my pistar. I'll let you guys know. I'll also look at the output of both settings and see if I see a difference with the visiplex encoder. My pagers are for sure Pocsag models...

Thanks

KD5HNM

KE7FNS
Pi-Star Team
Posts: 2429
Joined: Wed Apr 17, 2019 11:11 pm

Re: Narrow Band / Wideband

Post by KE7FNS » Fri Dec 03, 2021 11:53 pm

kd5hnm wrote:
Fri Dec 03, 2021 10:20 pm
and see if I can reproduce the scrambled text I'm getting from my pistar.
If you are seeing scrambled text its because your pager is using some weird character mode or maybe it has encryption enabled.

SDRAngel is decoding my testing text messages from MMDVMHost with no issues in either stock wideband or my custom narrowband.
If someones previous actions are any indication of their future actions, then I predict the deletion and removal of access will happen at any moment. 7-11-2020.

"07/13/20 This Website Has Been Taken Down" ... again :lol: and again

Post Reply