I guess I can declare K1 #1649 QRV on 10 meters, having worked HK3CQ and
VE3KZ Sunday with about 1.5 watts into a 40 meter Windom. This mod,
however, remains a work in progress (with occasional regress).
This has been an interesting and frequently frustrating project that seems
never to end as new discoveries keep popping up. Wayne suggested and
graciously supplied 26.170 MHz xtal to try low-side injection with
potentially lower cost and greater output from the premixer. This also has
the advantage of making the 10 meter and 17 meter premix filters identical.
The fun begins, however, in getting enough drive out of the bandpass filter
to achieve a useful output. I've followed the leads from Bob Larkin and
Stephanie Maks, both of whom reported achieving outputs over 4 watts;
however I'm unable to duplicate their results. Achieving 1 watt is fairly
straightforward, but 4 watts is not. The devil is in the details,
somewhere.
The 10 meter filter components are installed as Band 1 on a 2-band board
shared with 17 meters. The latter provides an excellent point-by-point
comparison and sanity check because some tweaks that enhance 10 meter output
destroy 17 meters entirely. At this point, I'm not sure the path through
the BPF output relay K2B behaves identically for both bands. The Band 1
path is clearly inductive and causes a significant voltage drop between the
junction of C14 & C15 and P2-pin 8. Capacitor leads display enough
inductance to make a difference at 28 MHz so that you get a false result
when you tack in a cap with long leads to try a change.
Would appreciate hearing from others wandering down this path.
Bill Cunningham, K4KSR
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