forum.pistar.uk

I have several Motorola Advisor pagers. I have them programed to the correct frequency, when I send a manual page with pistar the pager alerts but the alpha part looks garbled. The pagers are locked to narrow band, can't select wide band. Is there a way to select wide or narrow band on pistar for pocsag paging? Or any other suggestions on why my text is garbled? Thanks for any suggestions...

Older POCSAG used 512bps, 1200bps was later. Not sure if that might be related.

KE7FNS wrote: ↑

Wed Dec 01, 2021 5:28 pm

G8SEZ wrote: ↑

Wed Dec 01, 2021 5:18 pm

Older POCSAG used 512bps, 1200bps was later. Not sure if that might be related.

MMDVM_HS firmware states POCSAG 1200

https://github.com/juribeparada/MMDVM_HS

I hadn't looked, but it makes sense, 1200bps was in use at least 35 years ago when I worked on pagers.

Hey guys,

I did check and have the correct baud rate. I don't see anywhere in the pager settings to select 7bit data.

The pager does alert when I send a message to the cap code, but the text is just scrambled looking.

I have several pagers, motorola, unification, etc. I thought this was a motorola, but it's the Unification Alpha +.

Wondering if maybe there is a encryption key installed on this pager and that might be why my texts are scrambled.

I think the only programing software I have for programing of the Unification pager is the "Customer" version which doesn't allow me to switch from Narrow to Wide band. I can see where the setting is but it's greyed out...

I'll double check with another paging transmitter I have. I also have a visiplex paging transmitter, I'll try it this afternoon and see if the pager works with it.

Thanks for the help guys, and let me know if you guys figure out how to switch from the Pi-star side from wide to narrow...

Thanks!

J

KE7FNS wrote: ↑

Thu Dec 02, 2021 5:42 pm

kd5hnm wrote: ↑

Thu Dec 02, 2021 3:34 pm

let me know if you guys figure out how to switch from the Pi-star side from wide to narrow...

The ability to switch isn't possible currently and I'm not sure which it is currently using.

The ADF7021 data sheet should provide the answer. POCSAG uses FSK with +/- 4.5kHz shift on the carrier centre frequency so wide and narrow don't actually apply, it's purely the bit timing that decides the data rate. There is no attempt to reduce the edge speed to limit the transmit bandwidth because the allocated channels were deemed wide enough that modulation sidebands were all within the nominal channel bandwidth. Remember this was 1970s technology.

The modulation used is FSK with a ±4.5 kHz shift on the carrier. The high frequency represents a 0 and the low frequency a 1.

The ±4.5 kHz frequency shift is used along with a 25 kHz channel spacing, known as "wideband". Some jurisdictions require that all systems move to a "narrowband" configuration, using 12.5 kHz channels and ±2.5 kHz frequency shifts (for example, the U.S. Federal Communications Commission (FCC) has mandated this transition be completed prior to 2013.[3])

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?


Thanks again for your time and help.

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

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

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