4 decodes of WD2XSH/17 all -29
QTX and IRF540Z ( my last one i smoked 9)
this version has about 2500 pF G-S
It can run at 5A 22V with the highest output sofar
but at 100W input level everything heaths up coils and IRF
the antenna current meter relative 60-70%
must be close to 100W rf
the standard IRF540 measured 2700pF
this one is second best about antenna 50%
it is very critical in tuning the IRF540 starts in self oscillating mode then the output and current
sudden drops to very low
I can get 100W level with the QTX but on the edge and only with the Z version of the
IRF540 still have to fine tune with a piece of ferrit to have max out and good pulseform
it is not plug and play this QTX it needs fine tuning and some C values differ a lot with the original
i had to use C2 C3 15 + 15 nF and the loading C is 10nF + 6n8
plus a fine tuning of L3 with a ferrit rod is needed.
Until now every day i saw a different output and or tuning..
The type of IRF makes a lot of difference
This season only one time my QTX was decoded by WD2XSH/17
I know I should have build a heavier PA that is less critical ?
Awaiting mosfet drivers TC4422 type that can drive the IRFP4227 a heavier type FET
I tried the IRF510 this version has the lowest G-S capacitance of the 3 about 400pF measured
So this IRF510 should be the most usable RF amplifier
But no output with this setup and worse in standby receive the IRF510 still draws elevated bias current 0.040 The other IRF's do not have this leak current.
this generates 4-5 S units noise in receive
QTX IRF540Z 22V 4.5A
h=50V/dev Drain pulse 125V output 370V tt # 132V eff