Every now and then you find yourself adapting circuits to achieve almost the same end as a previous project. This circuit below is no exception.

Callsign beepers are essential for path lineups on microwave frequencies, and even beacon controllers. This circuit started life as a breadboarded controller for the VK3RST beacon. It’s still in use today.

The circuit consists of an Arduino Nano which I’ve used pins only on one side of the device as well as a 7812 to provide a constant 12v to the Arduino, This saves on header pins, but that’s just me. You can always use header pins on both sides. The rest of the electronics converts the 5v output on pin 16 to switched VCC at no more than 100mA on the collector of the 2N3905. If you want more current, you could swap out the 2N3905 for a 2N4402 for VCC at 500mA.

The circuit above is used to power a GALI84 driver stage which sits between the local oscilator and power amp on the 70cm VK3RST Beacon. It turns the driver on and off in accordance to the optut of the Arduino and is an ideal way of keying the beacon. If you’re interested, I’m using a MiniKits GALI-84 Driver amp.

If building uWave gear has taught me anything, it’s that spares are important. Whether it’s components or fully built-up spare boards, chances are something will fail down the track for no obvious reason. This happened to me on a hill recently when 3 FETs in a sequencer decided to self-destruct for a reason not immediately apparent. Swapping out the board with a pre-built spare took minutes leaving the faulty board to be repaired and readied as the next spare.

With that in mind, I decided to make some PCBs of the project for easy swapping out if required. Also, having the Arduino Nano in a header socket enables it to be swapped out easily if it needs to be reprogrammed for whatever reason. These boards will also come in handy for future projects as well. If you’re in Australia, you can buy the PCB and programmed Arduino if you like.

Parts

1 x Arduino Nano
1 x 7812 12v regulator
2 x 4K7 1/4W resistors
1 x 22K 1/4W resistor
1 x 680R 1/4W resistor
1 x 3mm LED
1 x 2N3904
1 x 2N3905
2 x 15 pin headers
2 x 2 pin headers

This Arduino Callsign beeper beacon controller uses a 2N3905 to switch VCC to the output. It can deliver 100mA. If you need more, you could swap it out for a 2N4402 which can handle up to 500mA. This device is designed for use as a general-purpose amplifier and switches requiring collector currents to 500 mA if you’re using the 2N4402 or 100 mA if you’re using the 2N3905.

Fairchild transistor datasheets for the 2N3904, 2N3905 and 2N4402 general purpose transistors are also provided for download.

The Arduino sketch I’ve used for the VK3RST beacon can be downloaded and installed on your Nano. The file is commented with where to change the parameters for your station.  You can also change the CW speed and mark space ratio if you like.

A shoutout and thanks to Mark VandeWettering K6HX whos code is the base of this sketch.