HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: Quinta on July 26, 2023, 0042 UTC
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I made couple similar beacons this summer, and want to share their construction.
Transmitters are primitive, 190-200 mwt output with 3.3V power from LiFePo cell, almost 500mwt with 6.3V from solar panel.
Charge current limited by solar panel, contoller only every 8 sec switch off charging and masure voltage on battery.
Controller - attiny85, voltage not stabilised, but limited with resistor and 4-5V zener diode. This circuit not draw power at night because maximum battery voltage is 3.5v. Attiny work with internal 1.1V reference voltage and internal rc generator, brownout level 1.8V Flashed via arduino as isp, with ATTiny Core for arduino. Actually program ismodified NicoVarg99 cw beacon, because program allow use not hardcoded text strings, so we can measure and send some telemetry. I only add voltages measuring and control charging circuit.
Boards covered with Plastic 71, bottom side of the boxes drilled for drainage and ventilation, because in closed boxes forms condensation.
https://github.com/NicoVarg99/Arduino-CW-beacon
Controller schematic
(http://hoshinokoe.ru/files/HF%20BEACONS/new27143khz_schematic.jpg)
First beacon, 27.143MHz
(https://sun9-75.userapi.com/impg/rqMAh3fp6bgoDc-Daqk3xLYKqQq3hgNmoUNJWA/xorFCgmdDQ4.jpg?size=1620x2160&quality=95&sign=b92ba24d9e2f794cbf20767f3192153a&type=album)
(https://sun9-42.userapi.com/impg/9uDA4s3yfNqbai3RClAR_CSOCFCTGyW-FHQIMQ/swwtCztiuOU.jpg?size=1620x2160&quality=95&sign=951dc0a2aaa919d38e4aae0633c7644b&type=album)
(https://sun9-16.userapi.com/impg/VDucfOyWRYkHYk7JNekSjOsM5pdzD5PO1QQVSA/42RossTSWsw.jpg?size=1620x2160&quality=95&sign=121a5b0922b8ebe736ef9c05fe1091b9&type=album)
Second beacon, 13.56MHz
(https://sun9-74.userapi.com/impg/u75OrwBuC_t0P9BdVNOZDEAmZ2t6EfOilDMFlQ/1qeCgvBw968.jpg?size=2560x1920&quality=95&sign=73871ac036fb5863fe4872f78d69b349&type=album)
(https://sun9-53.userapi.com/impg/gcUz6SK1ViNVndlKo_2OyIU0L3KFOLI8dftMcg/jigoqV-tzxI.jpg?size=2560x1920&quality=95&sign=b61060f6334b9ec266633453f1e8bb76&type=album)
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Very nice!