I'm pleased to say that my BITX20 is now complete and it performs
exactly as described. With my 132' doublet it has received excellent
reports incuding 59 from PJ4 in one direction and UN7 in the other.
Like Chris I made a few contacts with the penultimate (2N2218) stage
on its own and these included an island off the coast of ES which was
satisfying with 100Mw.
At first the PA was a little unstable so I put in a small (abt 45pf)
trimmer capacitor from the gate to the drain of the IRF510, lowered
the value of the 2.2K resistor between the base and collector of the
2N2218 by putting a 1K resistor in parallel with it and substituted a
300pf cap for the 0.1mf between the drain of the IRF510 and the low
pass filter. I now get 4 watts with a 12 volt power supply and 5
watts with about 13v from a 17 Ah storage battery.
I heard VU2PEP wkg most of North America (with 200 watts) the other
evening but the pile up was formidable. It would be nice to meet
another BITX on the air. Is any one interested in taking one along to
Rochdale on the 9th October?