40m qrp transmitter
Last night I finished up a version of the Universal QRP Transmitter from the book Solid State Design for the Radio Amateur. I changed a few bits here and there, but it is mostly the same circuit from the book. Here is the schematic that I ended up with.
The book used T50-2 toroids for the transformer and filter coil, bit I ended up using T37-2 toroids and adjusted the number of windings using the wonderful toroids.info website. For the oscillator transistor, I went with a 2N222, but any NPN small signal transistor should work. For the amplifier transistor I used a 2SC756 that I pulled from an ancient CB radio. From my limited testing, the output seems to be right about 1.5 Watts. I can probably increase that some with a little work and I still need to play around with the tuning, but so far it is working well.
As you can see from the following pictures, for the key I just soldered a switch directly on the board. My next project will be a homebrew paddle/keyer set. Once that is done, I will replace the switch with a 3.5mm jack and look at mounting this board in an altoids tin or something similar.