I have attached details of a high performance rocket recovery beacon I designed. It utilizes the LINX TXM433LR long range ISM module and a PICAXE -08 Microchip with the Revolution Education boot loader.
The file for my program is in the zip file. You will need the programming editor (link below) to run my file in emulation and/or to make changes.
Basically the program is as follows. There are two output pins from the PICAXE-08 PIC chip that connect to the TXM433LR (433.920 MHz) module and provide :
1) Transmit enable (a long duration HIGH pulse to PDN Pin from PICAXE-08 pin 6) and
2) Transmit (a short LOW pulse to DATA pin from PICAXE-08 pin 7).
These are pulsed to enable the transmitter in a CW mode to act as a long range beacon to be received on a TeleVilt UHF wildlife tracking receiver.
The program has two input pins (PICAXE pins 3 and 4) which when toggled LOW make changes to the CW by modulating with tones so that one can determine if a parachute has deployed plus another status input.
If you run it on the program editor, you can see the outputs pulse and you can toggle the input pins.
As far as the TXM433LR, it is probably one of those small chips you mentioned. I was able to buy (at a small premium) the same chip mounted on a daughter board with antenna and edge connector. This made wiring to a through lead board, much easier. The module requires a 750 ohm resistor for setting power level and 10 ohm resistor and 10uf capacitor to filter the power pin. I recommend the LR version modules as they are much more frequency stable than the cheaper versions. The TX enable (PDN) pin stabilizes the module by a high state activating the oscillator before transmission (DATA pin LOW) and saves power when low..
A word about the -08 Microchip. You must ground or pull up unused pins using a 10K resistor or the operation will be erratic due to static electricity. The onboard 4 MHz clock is used for timing.
The entire beacon will run a very long time on a CR123 3 volt lithium battery. The PIC will run fine on 3V, but requires 4.5 to program it. Conversely, the TXM433LR likes 3V and does not like 4.5V. So when programming, use one of the inexpensive programming/prototype boards.
I ended up making a fixture using a breadboard to program and test the entire beacon. It requires me to unplug the RF module when programming and adding a AA battery to satisfy the programming voltage. Pretty clunky, but it worked. I added 2 LED's to show TX enable and TX pin status.
The modulation is basically on off keying. When the program generates a tone it is by a fast square wave (LOW) on the TX (DATA) pin.
Let me know if you have any problems getting the program to run. It has been a long while since I worked on this project,
Revolution Education - Educational Kits, Robots and Microcontroller Systems
PICAXE Programming Editor (BAS805) - Software - PICAXE