Since some time the dutch POCSAG transmitters have been linked to the german DAPNET, Decentralized Amateur Paging Network. This network has been developed and rolled out as an initiative of Aachen University and is meant to be the replacement of the old FunkrufMaster. Just like the old system this network consists of a couple of ‘masters’, now called ‘Core’ where slave ‘Transmitters’ can connect with.
The easiest setup of a transmitter site can quickly be done. Necessary parts are:
- an FSK transmitter (439.9875 MHz and 4.5 kHz deviation);
- a Raspberry Pi (all types);
- a bunch of components
- 1x resistor 1k2 Ohm
- 1x resistor 2k2 Ohm
- 1x resistor 100k Ohm
- 1x trimpot 100k Ohm
- 1x NPN transistor
- 1x MOSFET pht6n03lt
- a piece of experimental PCB / breadboard / etc
- 3.5 mm jackplug
- an account for www.hampager.de
- UniPager software (here a description with links)
Using these parts a simple circuit can be created to change the audio of the Raspberry into a nice square wave. Using a MOSFET I’ve created a PTT-circuit, but this could also be done with a transistor. There are enough examples available on the internet.
Installation etcetera is well documented at the webpages of Aachen University and the corresponding pages on GitHub.
In the meantime I’ve built an all in one POCSAG transmitter, with all components fit into a 19″ rack mount. How this looks like can be seen at www.dutchamateurpagernetwork.nl.