Re: 80m hexfet power amplifier by W7ZOI

Timothy Fidler

Dan.,  I would be very concerned about using it without redesign for SSB use.  That diode to  the gate of the Mosfet is designed to be pumped low and keep the gate off during part of the cycle.  This is used on class C amps to improve efficiency.  What is the positive bias for - well that is an offset.  And note that that later bias is not stabilised 5V with a resistive divider as normally used.  The use of the Qsk receive cct at RH side again indicates it is intended for class C use . I followed the link but it is presented there as just a circuit with no palaver about the design intent.  the two band RF amp that AF presented elsewhere in the blog has a lot more going for it.   Suggestion ; look this beast up 

FQP13N10 Nch MosFET 100v 12.8A

FQP13N10 Single Nch Power MosFET ID 12.8A, VDS 100v TO220    .  It does have higher input capacitance the IRF 510 but it seems to perform well at RF.  The  current rating is twice that of the IRF510.   It is commonly available on EBay.

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