It works!

With the metalwork more or less completed, the PCB to hand and the software coming along nicely it was time to connect it all up and see what happened.

There is some serious electrical energy lurking around in this sort of kit, capable of making big (expensive!) bangs, so I wanted to carefully test out each stage as I went along. First up was checking that the power control logic was working OK, both hardware and software. As is the way with these things that showed up a couple of minor problems, or design mistakes as they are more properly known. A bit of hacking at tracks on the PCB soon fixed the problem that the PSU on/off control was working the wrong way round - on when it was supposed to be off. Note to self - you need the normally open contacts on the relay, not the normally closed ones... eejit! 

More and more components were added to the PCB as more functions were completed. The fan control software and associated circuitry turned out to be more of a challenge than it rightly should have been due to me forgetting which way up PNP transistors go. Once upon a time I understood all this stuff but I suppose I have been a software geek for too long now and I'm getting rusty on some of the electronics basics. Anyway, it's working now.

Eventually the PCB was fully populated and all tests completed. It was time to apply power to the amplifier. Scary stuff... mistakes could be expensive. In fact it was a complete non-event: the 50V and bias LEDs lit up and that was that. The RF side followed, with changeover relays , a 10dB pad on the amplifier input and the various coaxial cables to be connected. 

The amplifier lash-up ready for testing... wires everywhere!

An initial test with 10W output from the IC9700 (1W input to the amp) showed that the amp was producing about 150W output - an excellent result. Unfortunately, and to be expected, RF was now getting places it should not and it was time to apply ferrite rings/sleeves to the sensor lines to stop them jumping about, which seemed to do the trick.

Increasing input power easily pushed the output to our legal maximum of 400W without further incident. That's despite the fact that the amplifier is not in its case and has little of the screening that the completed unit will have. It seems to be a very stable set-up.

It was time to go on the air! Many thanks to Stuart, G4JHV for a useful series of tests, which suggest that all is well and the amplifier is not producing nasty sprogs or unreasonable splatter. Stuart is just 10km away and we had our beams pointing at each other, so this was a very harsh test indeed. Stuart was running low power but was pinning the IC9700 S-meter at the end stop.

So I seem to have a working amp, albeit something of a lash up for now. I plan to give it a more lengthy test in tomorrow evening's 2M UKAC contest and then, if all still seems to be looking good it will be time to complete the metalwork (holes for the fans, etc.), tidy up the internal hardware/wiring and get the amp in its box.

We're not done, of course! There is still a fair bit of software work to do and, as my software projects never really finish, that will be something of an ongoing challenge. I also need to calibrate the power output and SWR indications and to do that properly I shall need to find a suitable calibrated power meter. 

All in all a good day!