The AM Forum

What is the lragest tube ever made? I been wondering about this  for a while. I can't seem to find any thing anywhere.
Shelby KB3OUK

donnt know what the rating was but i know it  can be found between w8nb ears

The largest tubes that I'm aware of were made by Eimac. I don't have the type number but they made triodes and tetrodes that had a plate dissipation of one million watts. I did a calculation one time on how large a diesel generator set would have to be to run just one of these tubes. It turns out that it would require something on the order of 4600 horse power to do the job. This is just from memory and perhaps my estimates are incorrect.   

One of the most impressive sights I've seen was the VOA transmitter in Tinang, Philippines.  Their power plant was, as I recall, four GM 6-45 V-12 locomotive engines, about 2000 HP each.

It was almost 20 years ago but as I recall the transmitters were a mixture of TMC linear and COntinental plate modulated, probably 100KW.  There was a 20'X20' room at the end of the hallway for the spare tubes, stored in huge crates.  A chainfall and rail system along the ceiling allowed for hoisting the tube out of its crate and sliding it to the transmitter being re-tubed.  Never saw the actual tubes but by the size of the crates and the fact they needed a chain hoist to lift 'em, they were obviously strapping indeed.

The managers lived in Manila and commuted to/from Tinang via Cessna everyday, as Tinang at that time was a hotbed of Communist insurgency activity.  One time the Commies put a satchel charge on the base of one of the antennas; kind of blew the concret base to hell but the antenna never fell.  The dirt runway was a real white knuckler, with antennas at one end to clear and trees at the other.  The pilot ran that engine up to max takeoff as far back as he could on the runway then released the brakes for the takeoff run.

I think the biggest GLASS radiation-cooled tube ever mass produced was the 2000T. (2KW diss) Not sure about the external anus tubes though.

Johnny - your story reminds me of a time when I bought a Piper Arrow airplane. There we were, five of us loaded in the Arrow with the nutcase salesman/owner getting reading for take-off. It was a short runway.  He put the motor to full power, no flaps, and accelerated down the runway as he forced and held the nose down with the yoke. We were well past normal take-off speed. Then he jacked on the flaps full lift, slammed back the yoke and we sprung up like a jack-in-the-box into the air.  :o :o

My flight instructor looked at me in horror and whispered, "don't YOU ever do a stunt like that!"   ;D

T

you want to use a jet motor. The 300 HP starter I was working on runs .2 to .3 megawatt to spin up a jet that drives a generator to around 60 megawatts if I remember.

You might peruse the handbooks for the RCA 6949.  Pretty tough job for high power...

Here's one:

And, here's a 5 foot high tube from WLW:

I think I remember seeing a picture similar to the ones in the picture from WLW. The other tube looks like the kind used in XERA's 500,000 watt transmitter.
Shelby KB3OUK

Here's Terry W2PFY with the largest tube ever made.  Rochester NY Hamfest 2004!

Pete,

Do you think that maid would be available to come and dust off my tubes?

This web page http://en.wikipedia.org/wiki/Vacuum_tube (http://en.wikipedia.org/wiki/Vacuum_tube) says that the largest tube currently manufactured is the water/air cooled Eimac 8974.  Plate dissipation 1500 kw.

The data sheet is here http://www.cpii.com/docs/datasheets/78/8974.pdf (http://www.cpii.com/docs/datasheets/78/8974.pdf)

Reminds me of the sequence in "30 Seconds Over Tokyo" where they were training to take B-25s off an aircraft carrier  ;D

Yes, that and Midway are good flicks to watch after Tora Tora Tora

I don't know if this is the biggest tube or not but here are a couple of photos
of the RF area where I work.  The second one is the housing for one of our
water cooled Burle Triodes, the 7835.  We use these tubes to generate the
RF field for our linear accelerator to start the acceleration of protons to our
particle collider, at Fermilab in Batavia, IL.  Each one puts out roughly 5 Mw
of RF at 201 MHz to a 9 inch rigid line exiting the back.    It is driven via the 3
inch rigid line you see at the top of the photo coming down.    It is class C and
pulses at about 15 per second.

the first photo is a better shot of the 9 inch rigid line exiting the
tube enclosure.  just out of sight to the right is an elbow that takes
the feedline down to the linear accelerator on the floor below.

73

Rob / K5UJ

Do Klystrons count as tubes?  I was at WTIC channel 61 a number of years ago to their transmitter site. TIC had, if I remember correctly 5 klystrons in a row each at about 6 feet tall. Tons of plumbing to the  antenna. 

we need to get Gene W5CBS to fill us in on the sw tx he engineered in Palau .... the tube had a full time vac pump on it and the filaments could be unbolted and replaced ... said could do visual inspection with the fils out ... guess that qualifies as STRAP ...73 .... John

Fun reading on the largest.

Were nuvistors the smallest tubes ever made?
Did anyone ever make a tube as small as, say, a grain of wheat bulb?

I thought I remembered seeing a picture of some tube used by the air force that looked like a fuse(the kind with metal caps on both ends) but it wasn't as big around as a fuse is.
Shelby KB3OUK

- maybe a tube for a proximity fuse on a bomb or shell? 
have to take high "G's."  Smaller is better from a material, dimensional, volume/inverse cube effect, etc. where shock and G's are paramount.

...what a mouthful...  ;D    - you know what I mean.

(http://www.xcvcorp.com/New-4JPG.JPG)(http://www.xcvcorp.com/New-3.JPG)(http://www.xcvcorp.com/New-1.JPG)
Two different sub-miniature tubes, and Nuvistor---The smallest vacuum tube(invented by RCA in 1959)

Something else I wondered: What would you be able to replace a nuvistor with if one went bad?

You could check Ebay...

http://shop.ebay.com/items/?_nkw=Nuvistor&_in_kw=1&_ex_kw=&_sacat=See-All-Categories&_okw=Nuvistor&_oexkw=&_udlo=&_udhi=&_ftrt=901&_ftrv=1&_sabdlo=&_sabdhi=&_samilow=&_samihi=&_sadis=200&_fpos=Zip+code&_fsct=&LH_SALE_CURRENCY=0&_sop=12&_dmd=1&_ipg=50

Where I found 16 listings in auctions and 34 listing in stores for Nuvistors including a couple of homebrew amps and such.  Prices in the auction ran in the $10-15.00 range.

Plenty of room to experiment!

Found a thing on there that looks like a transmitter of some sort, they say it's an amp, but I don't think so cause it has a crystal socket on top and an rca connector which may be for a mic input. How did we go from talking about the largest of tubes to the smallest?  ;D

How did we go from talking about the largest of tubes to the smallest? 

'Cause I want to build a transmitter with the world's smallest tube driving the worlds largest GLASS transmitting tube.

As with all of my projects, I'm only missing a few parts:  The tubes and the money.

73, Barrie, W7ALW

Small tubes are for wimps  ;D

Well, I must just be a wimp.

The largest tube in the shack is easily lifted with it's handles.  It's an 8171, or 4CX10,000.  It's not glass, though.

The largest glass tubes I've ever run are the really wimby 450TLs, modulated by another pair of wimby tubes, the 450THs.  I'm rebuilding that rig right now.

When on the air in the past, that rig was driven by a 32V3.  I no longer own the 32V3, so I'm building a driver using a pair of really, really wimpy 35TGs.

Well, off to barbeque some hamburgers!

73, Wimpy, W7ALW

Dem Dar uns are big uns. No Wimpy there that's for sure  ;D