It¡¯s not really pointless to adjust the 20 M coil, with L10 used exclusively for 20 M band resonance. ?There is a threshold inductance value that will cause oscillation: correct inductance is essential in this design. ?It is possible, if the coil is so far out of adjustment (or DC open-circuit in the winding), oscillation will not occur, confirmed with no grid leak bias. ?Consider noting the present position of the coil¡¯s adjustment screw, then experimentally adjust this coil, without going beyond the mechanical stops. ?You can always return to the present coil position if an adjustment doesn¡¯t help.
Michael:
Thanks for making me take a closer look at this.? I was able to get one of my two 18Mhz xtals to resonate by running L10 in and out until the neg voltage popped up on the meter and then tweaking to peak it.? I also peaked the 15M xtal which had been resonating but not a? very high level.? Now all three, 40M, 20M, and 15M peak at pretty close to the same value, around -260-270mv, relative to the 80M value being zeroed out, per the book instructions.
The only problem I have now is that none of the crystals fit tightly into their sockets.? The 40M is so loose you'd think it would fall out if you held the radio upside down.? You have to push the 20 and 15 xtals around until you get them to a point where they oscillate and if they get jarred, they will most often stop oscillating until I wiggle them again.? Doesn't look like it will be easy, if possible, to get at the bottom of the xtal sockets and try to squeeze them a bit.? The access is awful and they're really small.? I'm open to suggestions on this.? Off hand I can't think of an easy way to add a mm or two to the xtal pins diameter either.
de John, K8NN
