Some things just work and thence become our go to circuits. Every homebrewer has these pet circuits. The downside is that we may never venture to newer or perhaps even better circuits.
The main concept behind my 7 Transistor PSSST_20 Transceiver design was to shun circuits used in the Bitx, EMRFD, TIA Amps and Facebook Groups. I was successful and this was a watershed moment to dare to be different.
While indeed there is nothing wrong with the aforementioned circuits, I wanted to challenge myself to coming up with a workable transceiver that was based on none of those. Right now, hams across the world are building K7TFC's kit based on my PSSST design.
One of the modules in the PSSST is a Driver Stage using the 2N2219A transistor. This device is a good substitute at HF for the now expensive 2N3866 or 2N5109. Incidentally, the 2N2222A (TO-18 metal can) has the same transistor specifications as the 2N2219A with a lesser device dissipation.
But the IMP TR design using mostly PNP transistors caused me to look at a PNP equivalent to the 2N2219A and indeed it has a PNP counterpart, the 2N2905. This took me to LT Spice and the following simulation.
PNP Driver Amp ~ 2N2905
Output at 15M
Make C3 equal to 5nF for a peaked output at 20M.
Making C3 = 15nF will drive the output peak lower in frequency for coverage on 40M.
A second "find" was purely accidental when inadvertently my bench supply was set to 24VDC, and I saw 20Volts PTP coming out of the 2N2219A. That my friend is 1 watt of RF. [20^2 = 400 and 2.5 X 400 = 1000 milliwatts.]
Enter the Mean Well DC to DC convertor where 9 to 18VDC input produces 24VDC at 600 ma. This converter is about 2 inches square and 1/4 inch high, something easily fit into your rig. About $21. I used this on a 15M radio for the IRF510 output stage.
If you up the voltage on the 2N2219A or 2N2905 then a really big heatsink is necessary as that device is running smoking hot. You also will need to tweak the Emitter resistor on the 2N2219A as it already is running hot with only 12VDC on the collector. But I leave that to you to experiment with and smoke a few devices.
The unconventional output from today's post: PNP RF amplifiers and higher supply voltage sources.
Keep on noodling as soldering is the last thing you do. Happy Friday.
73's
Pete N6QW