wild multi band HF and 6

[Opcom]

Any reason this would not work? (attachment)?

I have over-simplified it, but this fellow
http://www.qsl.net/i0jx/russian.html
started with a Russian 20-70MHz "6M military" amp and made it work, so...

The opportunity exists to try this, basing it on a 6M amp made from a "Henry" RF generator, then placing the HF coils and caps above the close-in 6M tank parts. minimum lead lengths all around.

[w4bfs]

hi Pat ....hope things are getting back to normal

aisi the problem with high power multiband arrangements are the unwanted resonances that get excited and make the amp unstable .... look at TMC GPT750 circuit and see how chokes and pinet parts were switched in/out to kill the parasites ... Henry Radio tried compartmentalizing the pinet with mixed success ...

the more poop you put in the bag makes a bigger mess when it gets stomped

[KD6VXI]

10 and possibly fifteen are going to be odd to tune up.

The 6 meter L is going to drop the impedance seen by the ten meter tank.  The amount is variable because of the variable L in series with Ctune.

Same trick used when the Cout and Cstray are high,  and you want to use ten or six meters.

Make the inductor have a hf preset,  or switchable,  for hf. Or,  have a vac relay switch between a hf tank and vhf tank.   That's probably  best bet.

--Shane
KD6VXI

[Opcom]

BFS - things are getting to as normal as they are going to. Luckily there are 4 offspring close enough to pitch in at Mom's, to drive her where she needs to go during the week, and do the cat boxes and other stuff, and I guess I have a pretty good part of this because I am taking her to church every week. It's the new normal. between this and working two jobs I have been pretty busy and that is why I am on here so late. I have the energy to do this but feel tired when it comes to building, lately. Especially with this rather large project. I am not too discouraged because the last big project took almost 5 years, the Tucker transmitter. All I need is time and the grace of God.

I can take your word on it for the GPT750 but will be looking at it. Bless the persons at TMChistory.org. Without them I would not have known what the GPT-10 tank coil was! People who scan stuff and give it away are nice. (OK so is Pete for publishing quality reprints even if he does charge!) A full blown TMC rig build-at-home is way more engineering than I want to do, and do not want to unintentionally make a Rube Goldberg setup either.

It may be best to have a relay switch between the VHF and HF tuned circuits. The writer of that article had only 6M and 160M, not the whole HF range. Maybe why he didn't have these challenges. I recall I'd asked about switching the tanks at the tube a few years before, and even made a sketch.. I don't know why I forgot that. It was before I got the Henry carcass or any of the big parts. It seems to have dropped off the search. But I'll work on another schematic.

One thing I want to do, originally for the HF amp, is to use the GPT-10 plate tank as intended, that is, at B+ potential. This was shown in a recent full schematic I think,  file
"_new-3cx3000A7_amp_v008.pdf"  -- As long as no one can touch it, and this is well-marked, and interlocked who cares.

So to switch the selector from the pi coils outputs to the plate.. It is perfectly fine to have two RF output connectors on the amp. Also two inputs if needed.

Question, will a good old Jennings vacuum relay switch take 5000VDC and How Many Amps? of RF current from the tube's plate to the tank coil?
If that pops it will be exciting.

Also I learned a very good lesson about short wires when rebuilding the Tucker transmitter. This is going to be the most serious thing.

[Opcom]

After drawing this (attach), and considering the advice.. you guys know more about building the special or big stuff than me..
A vacuum switch or even a mechanical switch of the right sort could be used to just short the 6M plate tank inductor.. be done with it.

The RF section drawing I just did is shown below. (does not include this HF preset or shorting the coil. maybe next one.. )

The whole proposed schematic including this is also there (version .009)

I'm also having concern now about how to make the variable inductor. The projects on the web are good examples but I have only a drill press, saw, and taps and dies. I think those builders had a few more tools. Still, it probably means only that I will use more elbow grease in making or trying to make the variable 6M plate coil. I have some acetyl resin or nylon rod 1" diameter, could put the shorted turn on discs of that. The projects also seem to show a PI-L circuit for 6M. Is it worth the trouble, will it help the cleanliness that much?

Patrick J