开云体育

Sorry for ignorance as an "advanced" class amateur, I'm naturally MORE amateurish ;-) but learning again...

L4 purpose is? Something to do with output transistors? Manual doesn't seem to make it clear in section 3.52 other than to say windings are not critical.

And what effects, if any, would a significantly higher or lower inductance than that recommended in the chart have, upon power output and/or durability of Q1-3?

For 30m, 14 turns are recommended. I measured (on my core, with my windings, thus it will NOT be the same for other people) for 14 turns 0.88uH, and removing 2 turns to 12 turns brought it to 0.79uH, very close to the recommended 0.78uH for 30m.

As I was, at the time at least, trying to make my QCX work (if repeaked) on both 20 and 30m, I removed a further two turns, not sure how low the inductance is now. Inductance recommended for 20m is 0.40uH. So, what effect would a too low inductance have on 30m operation? I plan to return it to get close to 0.78uH again.

I did blow my finals, but this was due to high VSWR when the wind (invisibly from ground level) transformed my doublet to an inverted L but being a manual balanced Antenna Matching Unit I was not on hand to rectify the intermittent and frequent swapping between low and high SWR until the smell of exploded Q(1-3) reached me.

Looking at the schematic, L4 appears to be a decoupling choke that works along with the .1uF capacitor C32 to keep RF off of the PA VCC voltage supply line coming from the transistors in the key shaping circuitry.? It needs to present a high impedance to the output frequency to keep RF flowing to the output filter, L1, L2 and L3 and not back into the 12 volt supply.? C32 shunts any RF that does make it through the choke (L4) to ground.? (This is a simplified explanation but basically that's what L4 is there for.)

Hans, correct me if I'm wrong please.

Jim - W0EB

Looking at the schematic, L4 appears to be

Jim,

Look at the assembly manual section 5.10

73 Alan G4ZFQ