This is a PICAXE 20X2 RFM42 Lost Model Locator Radio Beacon intended for locating lost Radio Control models using only the device and a suitable receiver.
When the radio beacon has determined it's lost, either by a failure of a pulse from the remote control (RC) receiver or by elapsed time, it starts transmitting a series of tones,. These descend in power and rise in frequency. These tones are heard on a suitable receiver. The receiver can be a scanner type receiver with narrow band FM capability or a PMR type transceiver. In between tones the Lost Model Locator goes to sleep with a current consumption of 10uA. The beacon is built on a PCB that is 25mm x 32mm.
The RFM42 module can transmit on any frequency between 240Mhz and 930Mhz at up to 100mW. The frequency of transmission is defined by 3 of the program variables f1, f2, f3 which are then written by the program into the RFM42 frequency setting registers $75, $76, $77 respectively. The frequency of operation must be chosen and programmed by the user. The RFM42 has various registers that can be set to compensate for frequency inaccuracies and temperature drift.
As you get closer to the radio beacons location you will hear through the chosen receiver more of the higher frequency tones. Fox Hunting is a sport practiced by amateur radio enthusiasts in which they locate hidden transmitters. Do a search on Google for 'Fox Hunting Body Fade' for some ideas on how to locate a hidden or lost radio beacon (the fox) using just a receiver. Body fade location is a lot easier if the receiver has an adjustable squelch control.
The detection range will vary a great deal depending on frequency, terrain, receiver sensitivity and transmitter power output. In a built up area of houses and the radio beacon on the ground (as a crashed model might be) at 430Mhz the short high power tone (100mW) may be heard from 1kM away. In open country with few trees or other obstructions, the usable range might be 5Km or so. The use of high gain antennas on the receiver such as a yagi or ZL special can increase detection range by a factor of 2 or more.
The RFM42 has a matching reciever, the RFM31, the pinout is the same. The direct modulation pin used is (RFM GPIO1) is available on a pad at the edge of the PCB, so a pair of these PCBs could be used as a transmit and receive pair.
When the radio beacon has determined it's lost, either by a failure of a pulse from the remote control (RC) receiver or by elapsed time, it starts transmitting a series of tones,. These descend in power and rise in frequency. These tones are heard on a suitable receiver. The receiver can be a scanner type receiver with narrow band FM capability or a PMR type transceiver. In between tones the Lost Model Locator goes to sleep with a current consumption of 10uA. The beacon is built on a PCB that is 25mm x 32mm.
The RFM42 module can transmit on any frequency between 240Mhz and 930Mhz at up to 100mW. The frequency of transmission is defined by 3 of the program variables f1, f2, f3 which are then written by the program into the RFM42 frequency setting registers $75, $76, $77 respectively. The frequency of operation must be chosen and programmed by the user. The RFM42 has various registers that can be set to compensate for frequency inaccuracies and temperature drift.
As you get closer to the radio beacons location you will hear through the chosen receiver more of the higher frequency tones. Fox Hunting is a sport practiced by amateur radio enthusiasts in which they locate hidden transmitters. Do a search on Google for 'Fox Hunting Body Fade' for some ideas on how to locate a hidden or lost radio beacon (the fox) using just a receiver. Body fade location is a lot easier if the receiver has an adjustable squelch control.
The detection range will vary a great deal depending on frequency, terrain, receiver sensitivity and transmitter power output. In a built up area of houses and the radio beacon on the ground (as a crashed model might be) at 430Mhz the short high power tone (100mW) may be heard from 1kM away. In open country with few trees or other obstructions, the usable range might be 5Km or so. The use of high gain antennas on the receiver such as a yagi or ZL special can increase detection range by a factor of 2 or more.
The RFM42 has a matching reciever, the RFM31, the pinout is the same. The direct modulation pin used is (RFM GPIO1) is available on a pad at the edge of the PCB, so a pair of these PCBs could be used as a transmit and receive pair.
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