80 Meter SSB - Part 3 - Transmit/Receive Switching & PA
I am currently in the process of building an 80 meter SSB rig modeled off of a series of ZL2CTM’s homebrew videos. I’ve added in some relays for transmit/receive switching and added a multi-stage power amplifier, the schematics of which are below.
I mostly copied Charlie’s work, but I substituted a handful of components for things I had on hand. The schematics below show the values that I used, but Charlie’s version had better performance than mine, so I’d suggest watching his videos if you want to follow along.
This is the layout that I ended up with for the power amplifier. RF comes from the bandpass filter through a relay and into stage 1 of the amplifier.
For the final two pairs of BD139s, I sandwiched them together between strips of copper board like Charlie did for some heat dissipation.
I’m only getting between two an three watts out with this setup. Charlie was getting around five, so I’m not sure what’s up. Admittedly, I changed some component values, but not by much. I’ll have to try and dig in a little deeper and see if I can figure it out. I may scrap the PA and maybe try a different version with an IRF510 or something similar.