Low Cost POCSAG Paging Network How-To

Are you sick of giving paging services your hard earned drug money just so you can receive pages?  Well then, now you can build your own paging network.

This is probably illegal, so if you get caught be sure to let me know so I can laugh at you.  It is legal in the hams bands though, if you're licensed.

Follow these simple instructions:

  1. Get the PE-300 POCSAG encoding program for DOS and play around with it.
  2. Get the PD-204 POCSAG decoding program for DOS and play around with it.
  3. Get a big old commercial VHF/UHF radio that is capable of transmitting +/- 4.5 KHz frequency shift keyed (FSK) data.  Don't forget the antenna and stuff.
  4. Hook your computer to the radio using this circuit (25k PostScript).  All the parts are available from Radio Shack.
  5. All control lines into the computer should have RF bypass caps and/or ferrite beads on them.  This is not shown in the schematic, same for the modulation lines.
  6. You'll need an oscilloscope to check that your square waves are clean.  Check output level by monitoring the discriminator tap of a receiver or scanner.
  7. The push-to-talk (PTT) key circuit won't work for all radios.  Experiment.
  8. Try to send and decode some test pages.  Use 512 bps speed rates and first to try and avoid any errors that will occur if your transmitter can't handle being FSK'ed that fast.
  9. You'll need to re-crystal or re-program your pager if you choose to use a commercially made one.

Radios

These radio are capable of being FSK'ed real hard.

Bravo Plus Receiver Board Part Numbers

138 - 143 MHz     AARD4050A
138 - 143 MHz     NRD7211A,B
143 - 148.6 MHz   AARD4051A
143 - 148.6 MHz   NRD7212A,B
148.6 - 152 MHz   AARD4052A
148.6 - 152 MHz   NRD7213A,B
152 - 159 MHz     AARD4053A

Pager Crystal Sources

Motorola Maxar Instructions

Modulation input:       Bottom of radio, near front panel, locate
                        () MOD printed on circuit board.  Apply modulation
                        input there.

Ground:                 Use the chassis ground.

Keying (PTT):           Top of radio, near front panel, locate J2 solder
                        pads (16 of them).  Solder PTT wire to pin 4.

Confirmed to work at 512, 1200 and 2400 bps.

Proper Pager Network Usage

  1. Get the capcode and frequency to the pager for your favorite system administator.
  2. Set your system up to transmit that same information.
  3. Spend all day sending anonymous messages saying online is down again.
  4. Barrels of fun!

Miscellaneous Links

[tax money at work]  Failed Clown College.