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Build a POCSAG decoder using a BRAVO receiver board instead of a scanner [message #39] Sun, 22 January 2006 23:19 Go to next message
root is currently offline  root
Messages: 207
Registered: December 2004
Senior Member


Build a POCSAG decoder using a BRAVO receiver board instead of a scanner
------------------------------------------------------------ ------------

NOTE: 02/01/97 - This is by an anonymous person. As I find out more, I
will add to and change this document, but for now, here it is, verbatim.
--Dr. Who

I use a pager receiver board configured to 'always receive'
to feed the serial port of my computer and monitor pages.
The receiver I am using came from a Bravo plus. It is part
number NRF4101B. My old Advisor uses the same receiver board.

This will probably not work with any other pager receiver board.

The receiver board sends raw digital POCSAG data, 0 V for zero and
3 V for a one, so you need: an op amp circuit to interface to the
RS232 port, a computer, and program to decode the data. If you
haven't experimented with PD-203.zip or some other scanner/computer
POCSAG decoder setup, you should investigate that first. This
document bassumes you have some knowledge about monitoring pager
transmissions with a scanner radio and a computer.

The receiver board connector has 8 pins. Pin 1 is the pin closest
to the corner of the board. Finding a mating connector is a problem,
the pins are very small and close together. Getting a connector from
an old pager is good, or use solid wire to jury rig something.
Depends on how rugged you want it to be.

I used 2 batteries for the power. The pager CPU board normally
doubles the voltage from the pager single 1.5 V battery to supply
3.0 volts. I just took the easy way and used 2 batteries. One
might try to figure a way to power the thing from the serial port,
I didn't mess with it.

The pin defs are:
1 3.0 V
2 ground
3 1.5 V
4 signal out, needs 1k pullup resistor to pin 1
5 ground
6 ground
7 ground
8 no connect

The dreaded ascii schematic! '+' means a wire connection.

(See file attachment)



Feed the signal out to your op amp circuit (see pd203.zip or
hamcomm2x.zip for details). The output of the receiver board
is a very nice square wave, probably cleaner than the one that
is coming from your scanner.

I built a box that has 2 batteries, a pager receiver board, an
op amp circuit, a switch for power off, and a 9 pin serial port.
That and my laptop make a very nice pager monitor setup.



[Updated on: Sun, 22 January 2006 23:20]

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Build a POCSAG decoder using a BRAVO receiver board - Discriminator [message #70 is a reply to message #39] Sun, 09 July 2006 01:40 Go to previous message
kc2nda is currently offline  kc2nda
Messages: 42
Registered: December 2004
Location: New Paltz
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I built this circuit, but modified it a bit. It works great fed into the computer's audio in.

http://www.hamradio.cc/images/forum/bravo_pager_schematic.jpg

http://www.hamradio.cc/images/forum/pager_discriminator_circuit.jpg

http://www.hamradio.cc/images/forum/motorola_bravo_plus_pager_decoder_circuit.jpg

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