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I could tell I was beating a dead horse when all the HFers ignored my earlier comments about plate bypass capacitors made of two metal plates with an insulating sheet between, and then when they kept talking about pi-nets while purporting to discuss V/UHF amplifiers. Some folks seem enamored by the view of lumped constants arranged and connected willy-nilly. But Hank, W6GGV, raised me knee-high on stripline design, and I've never forgotten the difference, nor how easy they are to design (not necessarily to build, however!). They'll just have to learn the hard way, I spose, just like I'm having to learn how to make holes in this desert cliche for tower bases.

I can just imagine one of these characters looking upon a typical V/UHF amplifier tank circuit and wondering "just HOW the hell can this thing possibly work?!?! How do you calculate the inductor in the output tank, fer Gawd's sake???"? 8-)

Steve, K0XP

Steve, K0XP said "Try a 3/4 wavelength stripline. Get the design info from W6GGV's articles published in the Nov. '80, and Jan. through April '81 issues of Ham Radio."

Thats right, Steve! a stripline is the way to go. Q is controllable and thermally there should be little or no drift as they warm up.? I worked with Bob Sutherland, W6PO, for a year and he helped me build a chan 13 television test cavity using a hugemongous 25kW tetrode. The input was a stripline. I am trying to remember if it was a 3/4 wave line, probably so.
The problem was in the output of the cavity, there wasn't enough room for a coupling loop. Capacitor coupled outputs allow harmonic energy to pass on out to the load and a high power filter would be needed. The project was shelved.?

I knew Russ Miller N7ART (SK) when he was building a 2M PA using a 3CX1200Z7. The 3CX1500Z7 was introduced about that time and would be a better tube if one was available (NLA?).? These are thoriated tungsten triodes with a grid flange, similar to the YC156 which was introduced before the 1200Z7 was imagined by the Salt Lake City bunch.
Attached is the N7ART article courtesy of the ARRL, it was in their handbook of unknown vintage, in the mid 80's.?
Input capacitance of the 1200Z7 is around 17pF, less than a YC156 but the same principle will work on the larger tube.
Russ used a Pi-L input,? I just looked at the article and remember him as we spoke often while he was working on the amp.
The benefit of using that tube is 4 second warm-up, not the 3 minutes needed with a YC-156, making it desirable if there was a sudden E-skip opening or moonbounce, otherwise why use a QRO PA on 2M for??

I have an unfinished YC156 amplifier that was built by a Italian ham who was a designer of broadcast transmitters. It wouldn't work for him at 144MHz. The entire thing is around 4 feet tall. The output uses transmission line with a copper pipe about the diameter of the YC156 inside a square enclosure. A copper disc on a threaded shaft tunes it and it has a copper disc adjustable closer or further away from the stripline for output coupling. At the time I could get YC156's that failed some spec for ham use, they were plentiful while MRI systems were using them but all that went away when the industry went SS and the ones showing up on eBay are generally burnt out by CB'ers.
Reid? W6MTF? ??