Digital Amateur POCSAG Paging

 

Send out digital numeric and/or alphanumeric pages for: Automatic weather alerts for Skywarn use; LiTZ / emergency alerts when linked to repeater controllers; club (function) meeting reminders; paging your friend to get on the radio; computer status messages useful in conjunction with packet radio gateways; and so on. Carefull reading of Part 97 [sections 97.3(a)(10), 97.111(b)(2), 97.305(c), and 97.307(f)(5)] makes it clear that digital paging is allowed for VHF and UHF operations.

It can be setup so hams could send the pages a number of different ways.

An DTMF interface to repeater controllers; Where a traditional user number is assigned to everyone with a pager. First enter the user number, then the numeric message which gets passed to the paging transmitter.

A packet interface; Either a web cgi, telnet prompt, or separate email address to accept numeric and alpha numeric messages which get passed to the paging transmitter.

A phone interface; An incoming line that would first: prompt you for a numeric password for protection, then a user number and finally the traditional numeric message.

Requirements:

A VHF or UHF radio


It must be capable of transmitting +/- 4.5 KHz FSK data. The transmitter must have a low audio response, around 20 to 50 hertz. You will need a direct (varactor or varacap) drive to transmit pages, and a discriminator output to monitor pages. Most 9600 baud "data ready" radios will work. The following radios are capable of being FSK'ed real hard:

A Pager Encoder

Here are two known options:
The Kantronics KPC-9612 TNC (Capable of sending POCSAG)
Or you can encode using a software computer program:
PE Clive Cooper's (G8UKN) POCSAG encoder for DOS - (local copy)

Pagers

You had two options here. Kantronics has discontinued selling their refurbished pagers. (They were about $100 a piece all set to go on the 2m or 70cm freqs.)

Now you have to have commercial pagers modified locally. If you decide to try it yourself and have access to programmers and test equipment, look for these types of pagers:

Motorola Bravo Plus, Motorola Bravo Classic, Motorola Renegade Motorola Lifestyle Plus, OI Electric Pocketbell, NEC

Your best bet is to stick with the Motorola Bravo Series. Make sure they are using the POCSAG protocol, not GOLAY or FLEX. Make sure they are 100 MHz or 400 MHz depending on which type of transmitter you are going to use. Try to get 512 baud in case your setup has trouble at faster speeds, also try to get the capcode and any programming passwords, you should be able to find these used pagers for under $40.

Local Copy of Misc Related Files:

PE-PAGER.GIF - Interface schematic for PE program
PD-205.ZIP - Shareware POCSAG decoder for DOS
PD-PAGER.GIF - Interface schematic for PD program
POCSAG.TXT - Explanation of the POCSAG protocol
DISCRIM.TXT - Where to make a discriminator tap in your model scanner (list) & more
all other files

Tips:

Addition reading/resources:

"Pager Handbook for the Radio Amateur" By: Philip N. Anderson, W0XI
"The Book of the CCIR Radiopaging Code No. 1" (CCIR-1) Radio Design Group, OR
QTH.net POCSAG mailing list/archive http://mailman.qth.net/archive/pocsag/pocsag.html
Kantronics new line of paging products http://www.kantronics.com/paging.htm
PE Clive Cooper's (G8UKN) POCSAG encoder for DOS http://www.cooperware.com/pe
PD Pete Baston's (GW0PJA) POCSAG decoder for DOS http://www.bearnet.demon.co.uk/pocsag
Henry Carl Ott's (N2RVQ) PIC/AVR based POCSAG encoders http://users.rcn.com/carlott/projects.html
Oliver Durm's (DL3SDW) Ham Pager Site - SAM http://home.t-online.de/home/dl3sdw/pag100.htm
Stefan Petersen's (SM0PHK) C-program for encoding POCSAG http://www.stacken.kth.se/~spe/projects/pocsag.html
Philips Pager Data Sheets http://www.semiconductors.philips.com/handbook/chapter_215.html