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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? ??

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? ??

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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.

Steve, K0XP

YC-156 is good up to 150 mhz.? ? It will be used on 144 mhz.?

?

Yes, the 8877 has a 38.5 pf? between cathode and grid....and is good up to 250 mhz.??

?

Question is.... how the hell do u make a tuned input for 144 mhz, with a whopping 92.5 pf of input C ??

?

With a conventional Pi tuned input....and an overall network Q of '4'? ?( input Q = 2.2)? ( output Q = 1.8)
It's then? C1 = 49.1 pf? ?L= .04 uh? ? C2 =? 56.1 pf?

The input C is WAY more than the? required C2 value.? ?Note this is based on a 35 ohm input Z.?

......................................................................................................................................................................................................................................................................................................................................................................................

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OK, here's what might work....increase the overall network Q to '8'? ? ( input Q =4.4)? ?( output Q = 3.6)?

It's then C1 = 96.8 pf? ?L =? .02 uh? ?C2 = 114.4 pf? ? Note, this is based on a 35 ohm input Z.??

trying to fabricate a .02 uh inductor will be a trick. A straight piece of copper strap might just? work.?

?

Jim? ?VE7RF

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A pi-circuit

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73

Peter, DJ7WW

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-----Original-Nachricht-----

Betreff: [ham-amplifiers] 144 mhz tuned input for a GG YC-156 ??

Datum: 2024-01-05T20:51:29+0100

Von: "Jim VE7RF" <jim.thom@...>

An: "[email protected]" <[email protected]>

?

?

?

?

?

YC-156 is good up to 150 mhz.? ? It will be used on 144 mhz.?

?

Yes, the 8877 has a 38.5 pf? between cathode and grid....and is good up to 250 mhz.??

?

Question is.... how the hell do u make a tuned input for 144 mhz, with a whopping 92.5 pf of input C ??

?

With a conventional Pi tuned input....and an overall network Q of '4'? ?( input Q = 2.2)? ( output Q = 1.8)
It's then? C1 = 49.1 pf? ?L= .04 uh? ? C2 =? 56.1 pf?

The input C is WAY more than the? required C2 value.? ?Note this is based on a 35 ohm input Z.?

......................................................................................................................................................................................................................................................................................................................................................................................

?

OK, here's what might work....increase the overall network Q to '8'? ? ( input Q =4.4)? ?( output Q = 3.6)?

It's then C1 = 96.8 pf? ?L =? .02 uh? ?C2 = 114.4 pf? ? Note, this is based on a 35 ohm input Z.??

trying to fabricate a .02 uh inductor will be a trick. A straight piece of copper strap might just? work.?

?

Jim? ?VE7RF

Ok, how does one go about building a tuned input for a 144 mhz amp, using a YC-156 tube ??
The input C on the YC-156 is huge,? 92.5 pf? ?( grid to cathode).?

This is for a cathode driven? ?YC-156

?

( The 1/2 wave tank for the output side is fine, and tunes up fine, with calculated RL.... to the 50 ohm output.)?

The output is not the issue, it's the input.?

?

What options, if any, do we have ?? ?What's the fix ?

Jim? ?VE7RF

KB1SEL got the premade chassis and cabinet from ICA manufacturing in? NJ.? They come completely pre-fabricated and ship flat. All you do is assemble with machine screws. On most of em, they have the outer front panel, and also a 2nd front panel inboard from the outer panel. Stuff like vac caps, verniers etc, is between the 2 x panels.... if you want.?

The pre-made cabinets come in every dimension you can think of.? ?Shipped in the flat pack, the shipping is cheap.? ?ICA runs flat out 6 x days a week.? That's also where the .515" thick teflon chimney for the 10 kw 6m, 3x6 amp came from.?

https://www.icamanufacturing.com/shop/cabinets

ICA Manufacturing

P.O. Box 677
Egg Harbor City, NJ 08215
(609) 965-9494

Chargercharger@...

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Keep in mind that sometimes, paying somewhat more for the chassis can make up for a lower shipping cost, too. Compromise, compromise, compromise...

Steve, K0XP

The Amp Repair guy has a few videos on Utube constructing a few amps. He purchase his chassis ready made. Check Utube for the name of the supplier. And yes there are metal suppliers listed on the web. You need to find a local one to save on shipping.

On Thursday, January 4, 2024 at 04:49:04 PM EST, Tim Fern <timjfern@...> wrote:

My little local town has Al. supplier who will guillotine pieces to size for free If the order is over ?10.... I expect most towns will have similar.

I never bend pieces (although my Al. supplier can do that too for a small charge), I just cut angle-ally pieces and drill / tap M4 holes.

18 or 20swg for tank circuits, 3mm (10?swg) for chassis/front panels.

best 73