Let me first say how blown away, honored, and delighted I am to be included in the final round of judging! The enthusiastic responses I've gotten from everyone have helped keep me motivated through the long hours of design and programming (honestly, this would have been a year long project or more otherwise). Thanks to everyone for your support! I've loved reading everyone's comments here on my project blog, on the final-five announcement page, youtube, and reddit.
Now then! Where were we. It seems like many people have been anxious to see transmit support working. I realized that some of the other features I'm excited about, like the Vector Network Analyzer, require the PSDR to generate signals, and of course, I want to see if I can talk to people with it! So, as you saw in the last video, I got transmit support started, but I was a little disappointed that the power output was so low (I mean, I knew it would be low but...)
So, I decided to try my hand at putting together an amplifier to go in the PSDR2's amp board socket (those five holes in the upper left), and this is the result. PCBs should get here next week, hopefully in time for the final judging. If it works the way I think it will, it should get us somewhere close to 100-200mW. Still not a lot, but enough to get a signal out, and maybe drive another amplification stage in the future.
It was fun to design. I'm trying some weird stuff here, for example, the two MMIC amplifiers are biased like a diode or transistor (well, that's what they are), where current is more important than voltage. Also, they like to be driven around 5-6v. So I needed a boost converter, ideally with a constant current output. Well. they make LED drivers that do exactly that. So that's what will be powering this little amp.
I'm actually not totally confident it will work on the first try, but it will be a learning experience either way.