Thanks to all for the on and offline responses. I made 3 versions - took sine wave from dds or took filtered bs170 then padded and drove into the comp pair per the UEP design or a tc4427/6 driving the irf640 - all designs look ok on the fieldfox but ill do some more in/out of band noise measurements.
Near 1/4 wave 475kHz loop is being driven at around 1A RF current at 25W @ 13V so all looks reasonable.
Laurence KL7L
If anyone has successfully used a Ultimate 2 or 3 to drive an external 500kHz class D PA direct from the DDS outpins or via the BS170 (say into a TC4426 driving a IRF640) Id like to hear about any pit falls/expereinces before I let smoke escape :-)
with thanks
One lonely decode last night WG2XXM 475.712 -31 @1006Z on L400B/25ft @ 4600Kms - sure was a noisy night. Nothing decoded non the NNE/SSW 1/4Y resonant loop - sometimes small is better :-)
Laurence KL7L WE2XPQ Alaska
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