PA4PA Beacon Project

(still under construction)

On this page you can find all the diagrams (and photos) of the PA4PA/b on 50452 KHz. It's not operational right now but it will be very soon.

BTW diagrams have changed over the last few days as there's a tripler in the second stage which has been changed now to a doubler (trifilar coil instead of bifilar and the bias is gone). So don't start building it as i'm still busy optimizing.

basic description follows!!

The beacon is build with very common materials that could be found in a good electronics shop.

The oscillator is a 3rd overtone with a crystal at 25226 KHz and a common BF199. The 40 pF trimmer can be used to adjust the oscillator just a little bit. 

The second part is the frequency doubling. Used are 2 pieces 2N2221A (or 2N2222A) also very common transistors. On this part there is a negative keying part for the beacon control with a BC557.

After the Oscillator I placed a very small low-pass filter for first suppression of the harmonics etc...

Then we get the first amplifier. As you see it are two exactly same circuits. In the first two stages I used an 2N2219 because it's has a very high hfe. The third transistor used is an 2N3866 and output is about 950mw. For the transistors you can use either those mentioned or for example the 2N3053, 2N4427 (with the 2SC730 as second you need only described 2 stages). Output levels will differ a bit but for sure you won't need to change the circuitry.

In the last part of the beacon amplifier I used the 2SC1969. Output now is about 5 watts.

The last part is the main low-pass filter to get rid of the last harmonics, spurs etc...

The beacon controller is the PK3 Keyer from Jackson Harbor Press.

(Don't forget to handle each power connection (to all parts!) with sufficient capacitors so the RF can't go from one to another part of the beacon. If you forget for sure you will get some self-oscillation and maybe your beacon will even sound like a East European bird (Tjirp Tjirp).