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The RF Workbench / Re: Hellschreiber beacon - with some oomph!
« on: February 17, 2022, 0253 UTC »Also tried this circuit from https://www.researchgate.net/publication/320623200_Notes_on_designing_Class-E_RF_power_amplifiers But i got no usable power from it.
My biggest problem with this paper and this circuit is that to specify a Class-E output network as he has without specifying a transistor is somewhat misleading; it fools the user into thinking that they can plug any old transistor (even a MOSFET) into it and expect it to work. Maybe this would work at 50 KHz with old power MOSFET transistors (which tend to have humongous output capacitance that swamps any other performance differences between models of transistors) but not at 6.9 MHz (as in the paper). The reality is more complicated and the component values of a Class-E network absolutely have to be tuned and optimized for each transistor at each frequency.
Also, it is humorous to me that this author does mention that he performed SPICE simulation but again without specifying what transistor was used and without providing any actual measured results to go with it. Had he substituted another transistor into his SPICE model, he would have seen exactly what I wrote above - the matching network has to be tuned and optimized for a particular model of transistor, which would make it obvious that specifying a network needs to be accompanied by naming the actual transistor used.
This paper is one of these garbage undergrad papers that people put out to pad their resume/CV; there's nothing new in there and it's lacking aspects that would make it useful to others. He references Sokol's book on Class E but then goes through a bunch of derivations that Sokol already did in his QEX article from 6 years before the book. I don't see the point.
I'm sorry that you wasted your time expecting this kid's navel-gazing project to work. That's a few hours of your life that you won't get back.
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