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#80m #qcx #qcx #80m


@CurtisM
 

Only getting about 3 watts from my QCX+ running 13.8 volts input.  adjusting L1 and L3 are having virtually no impact at all - even removing 6 turns from L1 is doing nothing at all.  I carefully checked all 3 terminals of the bs170 to verify each is in the circuit.  Search of this forum for 80m qcx power is coming up empty.

Anyone having success in adjusting their 80m QCX for 4-5 watts output?  I am trying to boost its output to better drive the QCX PA.  I will continue to experiment. yes I watched Hans tune up a 20m unit but this 80m seems unresponsive thus far.  

73 Curt wb8yyy


@CurtisM
 

okay forgive me for talking to myself here!  of course I should be focusing on L3 (the PA end).  removing about 6 turns on L3 and 3 turns on L2 has the power up to 4 watts.  been a few years since I checked the calibration on this wattmeter, but I trust the degree of improvement.  so next I am back to working on the QCX PA to see if I can bring it up also. 

if anyone else has experience optimizing their 80m QCX - you info appreciated to aid the gang.  80m is a blast in the winter - hence my interest in an 80m qcx+

73 curt


@CurtisM
 

 
progress!  4w on the QCX+ and now in vicinity of 20w on the PA. (Allison's judgment on the pin diodes 1n4007 may be in play down here, maybe when I run this later at 20 volts it will be easier to see how much that is in play). 
 
first on PA I tried adding 180 pF to the middle capacitance in the LPF - this actually reduced output power. 

I dropped 4 turns on the inner inductor L4 and that took me from 12 to 20w.  I am less confident in this scale on my venerable TT1202 as I don't use it as much (i think it is essentially a W7EL design).  as I was looking for dBs more than absolute watts - this little amplifier is useful now. 

I am using an improvised T3 made from a pair of FT50-43's (the original broken) so this might be a small effect (or not).  Curious what others get on 80m, but respect variability in our windings, pin diodes and measurements. 

73 Curt

 
73 Curt