What is the most powerful vacuum tube ever made?

I found a rather vague reference to such a horn under a history of the Saturn test (F1 engine). See Pg 94: (30.8MB) Reverberations of the Saturn tests were quickly felt. The acoustical impact was quite evident in the immediate area around the city of Huntsville, and the long-range sound propagation occurred at distances up to 160 kilometers. The result was a rash of accidental damage to windows and wall plaster, followed by a rash of damage claims (some- times filed by citizens on days when no tests had been conducted). Aware that climatic conditions caused very pronounced differences in noise levels and long-range sound propagation, engineers began taking meteorological soundings and installed a huge acoustical horn atop a tower in the vicinity of the test area. No ordinary tooter, the horn was over 7.6 meters long and had a huge flared aperture over 4.6 meters high. Its sonorous gawps, bounced off a network of sound recorders, gave acoustical engineers a good idea whether it was safe to fire the big rockets on overcast days.

There are some low quality photographs in the 500 page book, but none showing a big horn. However, I did find this photo: which seems to fit the aforementioned dimensions and description: I would have expected it to be much longer.

In another document, the sound level at the shopping center was measured at 118dB. I'm surprised it didn't break windows and ear drums. See Pg18: (1.3MB)

Yep. Big diesel powered air compressors were what drove such speakers. I vaguely recall that some were powered by a diesel train engine but might be mistaken. I suspect that the release of all that pressure would probably have frozen any water in the air and turned it into a snow blower. I don't recall any mention of that problem. Like a musical horn, the low frequency limit is controlled by the length of the horn, while the high frequency end is limited by the modulator. The Huntsville horn was trying in mimic the F1 engine(s), which according to the history, resonated at 5.25Hz. That requires are really long and probably folded horn. The battlefield horn carries voice grade audio, where the bottom limit was about 300Hz, and could therefore be much shorter.

I found the photo with an image search using: and the documents by manually groveling through: Note the quotes around "horn" which makes it mandatory to have the word "horn" in the initial search results.

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Here's the audiophile version of the Saturn 5 test horn: Clever design methinks but I don't think I want it in my house.

Trying to see what the 4.6 meter diameter test horn would do, I plugged these numbers into the calculator; Low cutoff frequency = 5Hz Throat diameter = 460 cm (4.6 meters) Steps = 25 which resulted in a horn length = 1692.3 cm or 17 meters long. That's much longer than the Saturn 5 test horn, which suggests that it wasn't intended to mimic engine vibrations.

Interactively plugging numbers for the low end cutoff frequency, I get: low freq cutoff = 7.9 Hz horn length = 756 cm Close enough. So, the big horn was good for about 8Hz.

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Jeff Liebermann     jeffl@cruzio.com 
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Largest continuous duty, that's relevant to your application (i.e. not RF) is the 8974, 1.5MW plate dissipation.

5kW is rather pedestrian for industrial applications; they're still being maintained and sold, probably on the cheap side of things. Commercial applications otherwise (like radiotransmitters) are basically all solid state now, for good reason.

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website:

I can't find it now, but I saw on youtube someone detecting significant amounts of xrays from a vacuum tube at 5kV. I think the problem is that most detectors are insensitive to low energy xray photons so people think there is no emission, but depending on the glass envelope, there might be, it is just hard to detect apart from by waiting for it to disrupt your DNA. Below 5kV there are definitely xrays within the vacuum tube, the question is whether or not they can get out. I would certainly suggest being very careful at even 5kV, and don't trust you xray detector to work for low energy xray photons, unless you have a good reason to.

Some geiger counters can also make good X-ray detectors:

I have a couple of those in use, of various types.

The continuous X-ray spectrum looks very much like black-body radiation. There is a distinct peak, which frequency direct proportional to frequency (hence inversely proportional to wavelength) to the electron energy (in keV), while in standard black-body radiation the wavelength is inversely proportional to temperature. When viewed on a log-log graph, in both cases the slope is steeper on the shorter wavelength side and so on. Some physics text books even suggests that it _is_ the same phenomenon.

At 5 keV, the total X-radiation is more than two orders of magnitude below that of 25 keV, so not to worry about the radiation at 5 kV anode voltage.

Up to about 25 kV, the spectrum looks just like black-body radiation. At higher voltages, there are discrete spectral lines (depending on target material), in addition to the black.body continuum.

RF tubes are OK as long as you can amplitude them. Just add an envelope detector (diode detector) and drive the speaker. Make sure you handle the detector DC bias issue.

Good point.

Follow-up question: is there a 100MW+ microwave diode out there? ;-)

Tim

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Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Design 
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Two orders of magnitude is not necessarily a sufficient safety factor. In a power amplifier I might well be running two orders of magnitude more anode current than a dental xray tube (there goes the "safety factor") and with no shielding that could do me a serious lot of damage within hours or less. The only options I would consider safe are either to calculate how much shielding would be needed and make sure it is there in the glass and metalwork, or obtain a detector that is provably sensitive to the wavelength of photons that could be present.

My newsreader truncated the last bit of the title of this thread; it appeared to read, "What is the most powerful vacuum cleaner ever made?" I was about to remind the OP to use an 'OT' prefix.

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significant

It should be easy to detect ionising radiation with an electroscope, and it is easy to build a cheap one of those.I remember doing it myself as a student, but I did have access to fine metal film, though not actually gold leaf.

Mike.

The shortest X-ray wavelength possible from 1200 V is 1 nm. The peak wavelength is slightly longer, definitely only soft X-ray.

At 25 kV, the minimum wavelength is 50 pm in the hard X-rays.

I did not find a direct evidence that the X-ray bremsstrahlung (BS) continuum behaves like black-body (BB) continuum, but at least in the BB case, the total energy is proportional to the forth power. If this applies also to BS, the total BS at 25 kV would be 160000 times stronger than at 1200 V. So a 1-2 kV actual anode voltage (not power supply unloaded voltage) would not be an issue, unless you stick your nose constantly among the tubes, not recommended :-).

Getting an electric shock in your nose is quite unpleasant and may affect concentration for a day. Done that, not recommended :-).

I have a few pen type radiation detectors like that, you charge the (electrometer) by pluggin it in into a unit, then put the pen in your pocket. At the end of the day you read the electroscope through a small window with a scale in the pen to see how much radiation you have been exposed too. Payed 10 Euro for the set.. Army surplus. Really nice stuff. http://217.120.43.67/nuclear/radiation_pen_IMG_6534.JPG

And that is a raspberry webserver.

Without meaning to state the bleedin' obvious, but energy in > energy out.

The energy of an xray photon is proportional to the accelerated electron voltage, which in most instances is proportional to V.

I have a vision of Jar Jar Binks in my mind after he paralysed his heads!

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Video Solutions Ltd 
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Much of the 50/60 Hz hum problem is/was due to grounding practices, especially with stage equipment.

- unbalanced signal connections were used

- the signal ground in each device was directly connected to chassis

- PE and N connected together into PEN in each mains socket ((TN-C) (- SCR controlled stage lights connected to same mains feed, same PEN)

Fixing these problems helps solve a lot of hum problems on 50/60 Hz, so why not on 400 Hz.

I admit that the ear is much more sensitive on 400 Hz than on 50/60 Hz, so more care is needed.

Listen on aircraft radio frequencies and you'll hear that 400Hz whine on a lot of transmissions. With a little care it could probably be avoided, but likely nobody cares as it isn't a safety issue.

When a similar system had 50/60Hz hum, you wouldn't even hear it as the typical communication receiver has a high-pass to filter CTCSS and the small speaker wouldn't do much at those frequencies. Of course that isn't true for a stage audio system...

Those RF power tetrodes have no problem with amplifying audio. This is only an issue with resonating tubes like klystrons, magnetrons etc.

** Annoying hum heard in live sound systems is at *many times* the local supply frequency. Typically a sharp buzz rather than a deep sine wave.

Radiation hum from nearby supply transformers into sensitive circuits like tape players and graphic eqs are only fixed by re-location of equipment - sometimes only a couple of rack heights ( 1.75 inches) does the trick.

.... Phil

Yes, some sort of ion chamber should be ok too and maybe less hassle to use. There are some designs on Charles Wenzel's site. But, some youtube xray hobbyists use a metal envelope geiger counter that might be very insensitive to