from the my-vacuum-has-a-bag-not-a-tube dept.
More than a half century later, traveling-wave-tube amplifiers still dominate satellite communication. That's right—your ultrahigh-definition satellite TV and satellite radio come to you courtesy of vacuum tubes in space.
Of course, there's a huge difference between Telstar's 3.5-watt, 4-gigahertz amplifier and one of the dozens of highly efficient microwave amplifiers on, say, the DirecTV-15 satellite, launched earlier this year. The latest generation of traveling-wave tubes can provide up to 180 W at frequencies up to 22 GHz, with efficiencies approaching 70 percent and rated lifetimes exceeding 15 years. Though their basic function is the same—amplifying RF signals—just about everything else has changed: the design, the testing, the materials, and the fabrication.
...
And now, ongoing research into a new and potentially revolutionary kind of traveling-wave tube—the ultracompact and ultraefficient cold-cathode TWT—looks poised to deliver the first practical device by the end of this decade. These are exciting times for vacuum tubes. Here's why.
No cheating this time--read the article to find out why.
(Score: 5, Funny) by Gravis on Friday November 27 2015, @04:23PM
vacuum tubes are just regular tubes that are born in a vacuum and space is the ultimate vacuum. see, they aren't venturing out into space, they're just going home!
(Score: 0) by Anonymous Coward on Friday November 27 2015, @04:29PM
they're just going home!
Note: Vacuum Tube died on the way back to his home planet
(Score: 2) by mcgrew on Friday November 27 2015, @11:22PM
Why is this silly, obviously not serious comment modded insightful? I'm curious.
As to the tubes, the ones the TV moguls use in space don't interest me, as I don't have cable or satellite, both of which are wastes of money. Made sense in the '80s but not in our digital world today.
What does interest me about it is that perhaps we'll get longer lasting, more efficient microwave ovens out of this.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by takyon on Friday November 27 2015, @04:56PM
http://news.sciencemag.org/physics/2012/05/return-vacuum-tube [sciencemag.org]
Throw those transistors away!
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 0) by Anonymous Coward on Friday November 27 2015, @09:38PM
SciMag has decent content but their page construction needs work.
They could start with the Skip to main content link--which is completely broken.
.
Their page doesn't mention the Nuvistor. [wikipedia.org]
That considerably shrank the size of tubes. [g3ynh.info]
I remember encountering those in the tuners of RCA TVs in the 1960s.
.
The other big downside of a tube is the percentage of the energy those use to light the filament.
These cold-cathode things are a giant step in the right direction there.
-- gewg_
(Score: 2, Funny) by Knowledge Troll on Friday November 27 2015, @05:20PM
I love RF! It makes almost no sense on an intuitive level at all. Humans were absolutely not made to understand a pile of photons turning into a voltage potential and back billions of times per second. Another place that vacuum tubes are in heavy use is high power terrestrial broadcast systems like FM radio and TV. Vacuum tubes still win there because of their resilience to error and total output levels are more expensive to implement with silicon. I personally have a goal to learn how to build a high power class A amplifier from tubes for ham radio use. Tube amps can run on antennas that would otherwise require another piece of gear besides the amplifier (antenna tuner) and scale to higher power easier.
Designing and building a tube amp is still wholly possible for a person in their garage. They were doing it in the 30s and the tubes are still on the market. The knowledge isn't exactly spread around everywhere though.
One of my friends had the best single sentence description for radio waves I've ever heard:
Anyone who does not believe in magic is welcome to take a crack at RF.
(Score: 0) by Anonymous Coward on Friday November 27 2015, @09:41PM
The sound coming of a tube amplifier is sooo good... and it looks cool especially without cover in the dark.
(Score: 0) by Anonymous Coward on Friday November 27 2015, @09:45PM
Class A - The device is conducting all the time, deviating from its Q point, up and down its load line.
This is the least efficient amplifier configuration.
Class B - The device is conducting 50 percent of the time.
The active devices are typically used in pairs (push-pull), with each half handling half the waveform and the halves are added (typically with an output transformer) to increase the output voltage swing.
Class AB - The device is conducting slightly more than 50 percent of the time.
This gets rid of "crossover distortion" at the zero-volts part of the waveform.
There have been tons of audio amps built using a pair of 6L6s in a push-pull configuration (and a big honking output transformer).
Class C - The device is conducting less than 50 percent of the time.
(It spends most of its time in the Off state.)
In RF circuits, you hit the circuit with what is effectively a pulse and you let the circuit "ring" for the rest of the cycle at the resonant frequency which you have selected via the physical dimensions of the passive components.
(At "lower" frequencies, those are inductors and capacitors; at higher frequencies, waveguides are used.)
Class C is the way to get high efficiency.
Class A is the complete opposite.
.
their resilience to error
That's the big one right there.
In a previous life, I repaired electronic organs.
Take a church that is in the middle of nowhere and give it a spire that is the tallest thing for miles and miles.
It is going to get hit by lightning, no 2 ways about it.
Now, put an electronic organ in it and have an organist who doesn't leave it unplugged when not in use.
Their chances of having to call me were greatly diminished if it was built with tubes.
-- gewg_
(Score: 2) by BK on Friday November 27 2015, @06:33PM
That just sucks....
...but you HAVE heard of me.
(Score: 2) by richtopia on Friday November 27 2015, @07:02PM
Soylent News has more parallels with scholarly articles than clickbait news in my opinion, and when we have summaries that taunt our viewership to read the article it degrades the site.
The summary has many similarities with the abstract of an academic paper. However in an abstract you can expect the major conclusion of the paper presented. I guess that is not what we can expect from Soylent posts.
(Score: 0) by Anonymous Coward on Friday November 27 2015, @07:46PM
That's because phoenix hasn't read it, and want you to tell her what it says.
(Score: 2) by Phoenix666 on Saturday November 28 2015, @01:43AM
No taunting intended. I'm not a ham or audiophile, but I have a couple friends who are and they love vacuum tubes. I thought the article might be interesting to other enthusiasts so I submitted it, but I honestly don't have the background in the subject to have summed it up with any justice.
Washington DC delenda est.
(Score: 4, Informative) by Techwolf on Friday November 27 2015, @08:17PM
So many folks think that, but its not. RF amps works with both digital and analog singles. To really get technical about it, "digital" singles don't really exist, it is a analog single with digital data encoded on it instead of a analog single encoded on it. This is why old satellites could handle all the new "digital" data singles.
It is the same trap folks fall for "digital" coax cables vs. the old cables. There is really no difference in the materials and how made, just the word "digital" added to the packaging.
(Score: 0) by Anonymous Coward on Friday November 27 2015, @09:50PM
"digital" singles [...] analog single
I'll take 5 of each please.
s/single/signal
-- gewg_
(Score: 2) by mcgrew on Friday November 27 2015, @11:27PM
I don't know why people don't get that. The same with CDs and MP3s, "digital sound". There's no such thing, all sound is analog. The only thing digital about it is the way the analog signal is stored.
mcgrewbooks.com mcgrew.info nooze.org