Class E PA designs

Today I made a first proper attempt at a QRP class E PA design for 136kHz. Although the values in the output circuit seemed to tie up well with theory I wasn't able to realise the expected high efficiencies, possibly because of the gate drive design. In fact I managed to blow up my last IRF510 because it got very hot and this meant aborting a WSPR test (at a sensible power level).  One resource recommended to me is http://www.alan.melia.btinternet.co.uk/classepa.htm which has a E class design spreadsheet. 

I also discovered today that 16mm diameter 3C90 toroids do NOT make good LF PA output bifilar transformers: they get very hot. The larger diameter 3C90s appear to be fine.

Overall, a frustrating day!

Class E MOSFET PA for 136kHz

I'm trying to optimise an IRF510 MOSFET PA for use in the 136kHz beacon and later transverter design. Alan Melia G3NYK has a very useful page on practical approaches to class E designs for 136kHz at his page http://www.alan.melia.btinternet.co.uk/classepa.htm together with a useful Excel worksheet to come up with practical values for the output network. Class E using square wave drive on the input can produce very good efficiencies, thereby reducing heatsink requirements.