An HF amplifier idea and example.
Last year I made a CW kit that was plagued with second class components which earned me an Official Observer Card for frequency instability and chirp. and an RST of 578c. This spooked me and really squelched my tinkering and building ambitions. Until this BITX40 came along and someone on our local Tech Net recommended I get this thing. Well this someone talked me out of getting an amp kit for it because of the very low input rating.?
Well, I have seen a hack or project page with this same linear amplifier kit used on the BITX40. And I can't find it for you today. The reason I mention it now is the reference to using an amp in the instructions about adjusting the power output for QRP or an external linear amplifier. This kit and some others i've looked at want very low input levels. This one wants 1-5mW. I have wondered how this could be done with what I have. Perhaps pick up the RF signal before it gets to the final? What would be the power level at the drive transistor? In regards to the BITX40 I have seen the power output drop all the way down to nothing when turning the RV136 all the way down to the right (clockwise). ?As for measuring 1-5mW of power out, you might have to use special equipment and some math. And maybe some expert advice.
But here is a bit of kit to think about. This one is called ?DIY KITS 45W ssb linear power amplifier for transceiver HF radio AMP
I put the name up because links tend to die on Ebay?. So here is what I was talking about-
http://www.ebay.com/itm/2017-DIY-KITS-45W-ssb-linear-power-amplifier-for-transceiver-HF-radio-AMP-/121754204165?hash=item1c591db805:g:TS4AAOSw14xXFFS9
