Sunday, September 23, 2012

13cm Amplifier

Having finished the 13cm Transverter it was time to consider an amplifier. Searching in the wardrobe  I rediscovered the metalwork that I assembled for a 13cm 13.8V PA module that was the driver module inside the Spectrian amplifier which was being sold by PyroJoe on ebay. I had mounted it on a heatsink and done a quick test when it produced 20W but it needed finishing

I added connectors, relay switching and a bargraph LED power meter on the front panel. With 5mW of drive it produced 18W but could not be persuaded to produce 30W.  One pin of the PA module needs earthing to activate the PA but another pin needs a voltage to supply the bias. I was applying 12V as it was available and I assumed it just needed to turn the bias on. Just in case, I dug out the email from PyroJoe with the pinouts and I noted he specified 28V. I hooked up a 28V power supply to the bias pin and sure enough the amplifier produced 32W with 5mW of drive. Looking in the PCB box I found a 2x1" chinese 12V to 28V(adjustable) DC-DC converter which I managed to squeeze into the box and it still produced 32W on 2304 and 2320MHz.  All that was needed was to make a cover for the box; another finished project.

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