Jim Said:

maximum mesh for maximum RF output. On 160, 40, and 20m meters the loading
variable capacitor must also be at maximum mesh. This makes me think my
PI-Network is not correct for the impedances involved, and then it sure
appears that the Dentron documentation does not match my rig. I might
have
to reverse engineer that PI-Net.

Tom's reply:

It was never engineered in the first place. It is seriously lacking on
inductance.

Jim's reply:

Tom,

Thanks for putting this all in perspective for me. Your description of
the high Q, and resultant heating of the loading capacitors, and detuning
makes sense. Users have reported much higher peak power than RMS with these
amps. I always attributed that to the voltage doubler, and B+ sag under
load. That is probably the dominate factor, but apparently RF losses are
significant as well after a sustained key down at 1 KW input.

So what is your opinion about the tank coil being wound of stranded and
insulated wire where the wire strands are silver plated, and Teflon
insulated? They are also close wound where the turns touch each other? I
have never seen that done before.

It sounds like I need to hit the charts for pi-networks, and pick the Q,
and I/O impedances, and then make it happen. The inductance of that orange
160-80-40m coil with Teflon wire will be hard to model. I will try to
measure it with my RF bridge, and see how it comes out (uh / 10 turns).

I have 2 large 400pf 2500v silver micas, and a strange 4 section variable
mica variable where each section is 300pf. This item has a common stud, and
each section is about 1" diameter, and 1/4" thick. I might be wrong, but I
recall someone saying these were used in the ART-13. These capacitors should
handle lots of RF current, but I'm not sure of the voltage rating of that 4
section mica variable capacitor. The Dentron 1000pf loading capacitors are
CRL type 858S, 5KV, X5U. These are best for bypassing use, and have high
dissipation factor, and high capacitance drift as it heats up.

Regards,
Jim