Pickle Jars and Vacuum Tubes

Why not make a tube? Well there are lots of reasons to not make tube, but I am unreasonable.  

...Slowly making progress. I may need to go to a coaxial layout in order to get gain. This one passes a signal--inverted on the plate load, as it should be--but is only about 1/2 the amplitude of the grid signal.
I gave up on metal filaments. Tungsten is too hard to work with. I switched to carbon in the form of a graphite mechanical pencil lead. The work function of carbon is a little lower than uncoated tungsten, too, so I can run it a bit cooler and still get decent emission. It's a power hungry little beast though; it draws about 8 amps at 12 volts, hot.

The brass fitting partly seen at the top is the vacuum port.




This carbon filament has several hours use on it and still looks perfect:

I admire your hutzpah. You have more energy than I do. I think I've done well to pull a tube out of the box and test it, let along build one. Good luck.

WC

Nah, I just don't watch much TV. I'd rather do something!

Wonder how structural carbon fiber would do for a filament?

It, lamploc, and, many other things were tried by Edison while working on the electric light. Most failed quickly. Carbonized thread worked best.

Eventually, Tungston was found best.

That is what I was thinking. The process for making carbon fiber resembles what Edison used in making the carbonized filament. It should work well in a diode as Edison stumbled upon it when trying to keep the carbon deposition from covering the bulbs' interior. He modestly called it the Edison effect.

Graphite pencil lead works far better than anything I've tried so far. I have had hours on my pencil lead before I broke it making adjustment inside the tube.

Getting a deep and uncontaminated vacuum seems to be the hardest part right now, unless I invest in an oil diffusion pump. They can be had used from labs for a couple hundred bucks on eBay, and there is little to go wrong with them, but I don't have the spare money or inclination to buy one right now.

I am going for a concentric layout this time. Trying to get gain when electrons are going around the grid instead of through it might be an issue.

That work is quite impressive! What are you using for the envelope?

Very nice!

I'm sorry, but when I asked about the envelope, I should have asked if you had any ideas on a container that would retain the vacuum permanently yet. I know it can be hard to get and keep a high vacuum. I used to work in high altitude simulation of high voltage power supplies and made up some of the seals and ports. The results you are getting are truly impressive and I am sharing the descriptions with the folks here at work.

Thanks fellas!
I am using a new Kerr, "self sealing" canning jar. They will hold vacuum for as long as you want to store food in one, I figure. I am leaving the evacuation port in place and valving off the pump at the jar lid and capping it. That way I can remove the pump and get it out of the way, but re-evacuate the jar as needed.