6
$\begingroup$

I recently bought this tube for use in an art project and would like to know what it is and what it was originally used for. Unfortunately, the silkscreen labelling on the glass envelope was worn off and unreadable and there are no other obvious identifying marks on it. The tape measure indicates scale (it's big!). I'd also like to find a source for more like this, since it has generated a lot of interest sitting on the shelf in my shop.

$\endgroup$
  • 2
    $\begingroup$ Wait -- insulated color-coded wire on the feed-ins? Might be an instructional demo that doesn't actually amplify (or has a very conventional tube hidden inside so the demo can be live). $\endgroup$ – Zeiss Ikon May 31 at 11:20
  • $\begingroup$ Are there any markings? I see "4816" on one of the inside metal pieces. It looks like there is some white lettering on the right side of the glass that could be useful. $\endgroup$ – Chris K8NVH May 31 at 16:59
  • $\begingroup$ Those black, red, and yellow wires could be from a computer power supply cable. If so, that dates the tube (or its base modification) to ~1990--present. $\endgroup$ – Mike Waters May 31 at 17:32
5
$\begingroup$

This looks like a JAN-CTL-5948A, found via images within the search results for "huge vacuum tube".

ITT Electron Tube Division JAN 5948A Hydrogen Thyratron image from Lamps & Tubes website

According to the linked site (from which the picture is also taken):

The primary application of this tube is in high power, high voltage radar modulators. The 5948A is capable of supplying 12 megawatt pulses in this service.

The datasheet indicates that it's a bit beyond a typical vacuum tube:

The special features of the 5948A include an internal hydrogen-reservoir capable of producing a wide range of hydrogen pressure […]

Some online listings title this as a "Industrial High Power Early Warning Radar Military Hydrogen Thyratron Tube". I couldn't recommend trying to get it working ;-)

$\endgroup$
  • $\begingroup$ Excellent, Nate! Anyone know whether it might it have any potential amateur radio applications? That being said, radar is illegal on the ham bands. $\endgroup$ – Mike Waters May 31 at 20:34
  • $\begingroup$ @MikeWaters isn't experimental RF usage, including radar, OK, in some form? $\endgroup$ – Marcus Müller Jun 1 at 7:49
  • 1
    $\begingroup$ @hobbs-KC2G but it is a thyratron, not an amplifying tube; meaning that it's not designed for continuous, but pulsed operation. I must admit that "being able to dump a lot of current for a short time" isn't exactly what I'd be looking for in many applications, especially since, as gigantic as that thing is, its pulse duration with > 1.25 µs isn't really all that short (roughly equivalent to 8 MHz of bandwidth, which is practically nothing for modern radars). $\endgroup$ – Marcus Müller Jun 1 at 7:59
  • $\begingroup$ … and that it's "cooldown" period only allows for maybe 1500 pulses a second. In other words: can't even use it for fast on-off-keying sensibly. If I use 8 MHz to transport 1.5 kbd of on-off-keying, someone will hopefully be angry with me. At the same time, if I have these 8 MHz of bandwidth, and only need to be at least that good in data rate, I can have a spreading factor of more than 5330 – about 37 dB of processing gain, meaning that a 37 dB lower averager-power transmitter system performs just as well. And that's a lot easier to build! $\endgroup$ – Marcus Müller Jun 1 at 8:11
  • 1
    $\begingroup$ @MikeWaters my understanding was that yes, staying in the designated bands and adhering to the cooperation rules and the identification necessity, amateur radio licenses can be used for the purpose of experimenting with radio technology, even if not for the purpose of communication. $\endgroup$ – Marcus Müller Jun 3 at 5:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.