brainwagon

Today, I felt some compulsion to work on something radio related. A couple of weeks ago I build the crystal oscillator from Chapter 1 of Experimental Methods in Radio Frequency Design. I was lacking the necessary toroid to continue building the buffer amplifier, so I had ordered some from Doug Hendricks at qrpkits.com. They arrived a few days ago, so I really didn’t have any excuses to not just finish building the buffer amplifier.

To make a long story short, it appears to work! I’ll try to get some video/pics of it up here shortly. I did a pretty mediocre job of planning the layout, so the board looks pretty crufty, but it does work. Previously, I had tested it by attaching a clip lead to the base of the oscillator transistor. It sounded fairly loud in my FT-817, but the waveform sounded really squirrely. Now, when I clip in amplifier, it sounds really, really clean, even when I attach the clip lead to the output of the amp.

I haven’t had a chance to try to measure the output power yet, but it’s probably in the 10-15 mw range. The circuit in Chapter 1 includes a final class C amplifier stage, which is probably next on my list, along with a final harmonic output filter.

Addendum: If my calculations are correct, the output power is around 19mw (at least, to the precision of my crude RF wattmeter that I constructed).