The circuit design I used for this is courtesy of Wayne McFee NB6M and he calls it the
"NB6M Miniboots" and it is now available from NorCal as a kit.
I needed something to get more oomph from my Tuna Tin 2 and since it was running on 40 Meters that's what I built this for.
The heart of this amp is the IRF510 Power Mosfet Transistor. If you have Acrobat Reader here's the Data Sheet: IRF510.pdf Otherwise just believe me that it's a usefull little gadget. (They're also available at Radio Shack for a little over a dollar.)
The band and power output level for this design is determined by the output LC network. (see tables on NB6M's page.) I used solder turrets to mount the caps and coils so it would be easy to change them out. I'm going to explore the possibility of fitting them on a 14-pin DIP header. That would be cool.
The circuit is very simple, here is a different way of looking at it without the RF sensing relay-bypass portion:
The RF-sensing Relay-bypass circuit responds very well. I used an Omicron I had kicking around that had a coil resistance of 322 ohms. It fits in a 16-pin IC socket so I put a rubber pad on the lid to keep it from "dit-dah-ing" out..
I mounted the drive trimpot on the bottom of the circuitboard and drilled a hole in the top of the enclosure to access it.
Here it is setup for action with the Tuna Tin. NB6M says it requires 1 watt to drive this thing.
My Tuna Tin puts out about .7 watts and has a bit of harmonic distortion.
This baby cleans it right up! And I get a little more that 5 Watts to boot!
(Maybe that's why he called it MiniBoots?) Thanks Wayne!
By the way, that's my Dads name (God rest his soul.)