The beacon is 100% homebrew with a crystal oven and PIC microcontroller. It is capable of 6 modes of operation CW, DFCW, S/MT-Hell and QRSS versions of the same.
It is currently set to slow Hellscheiber, 10 minute transmit period. Output power is 500mW.
Its transmit string is 'MW0UZO IO81JL'.
Its life began as a breadboard with a 16F628A microcontroller, 20x4 LCD display, some switches, a crystal oscillator and a few RF amplifier stages.
Then followed many hours(days? weeks?) battling with PIC assembler and flakey ICSP to get it all working...
The next part was to build the crystal oven module. It is built into a small plastic case and contains the oscillator with varicap tuning, buffer amplifier, 1 bit DAC for the tuning voltage and a 9V regulator. It wasn't easy squeezing it all in there.
The heating resistors sit either side of a thermistor with some heatsink compound and an insulating rubber washer covering them. On top of this sits a piece of copper onto which the crystal is soldered to. The thermistor is connected to a comparator on the PIC, which compares the voltage with an internal adjustable reference. The PIC then controls the heater to achieve the required temperature. Once it is near the target temperature, the heater is pulsed to avoid overshooting.
Then the mainboard was tackled, removing parts from the breadboard, fitting and testing as the circuit was rebuilt. Its not a PCB, it is built onto copper clad, through hole style with components fixed with epoxy where necessary and all interconnections are made underneath. It looks tidy from the top and a mess from the bottom! With its IRF510 RF amplifier, it can deliver over 5W if necessary.
With the rear wiring hidden, the internals look great.
Most aspects of the beacon are adjustable via the menu. You can change timings, turn the beacon on and off at certain times, adjust the oven temperature or disable it, adjust the frequency of transmission, adjust the message and modes of operation and adjust the backlight. It can be set to work in a single mode, all standard modes, all QRSS modes and all modes. The backlight can be set to switch off to save power.
Here is PA2OHHs excellent homebrew grabber showing the beacon in QRSS CW mode and QRSS textmode.
It is planned to install the beacon into a weatherproof case with clear front, battery, charge controller and solar panel.
Click here to visit the facebook Radio Beacons group.
Thank you to all stations giving reports!
14/05/13 - PA0TAB Johan, Netherlands
06/05/13 - DL8WX André, nr Koblenz, Germany
05/05/13 - S52AB Joze, Slovenia
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