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#1
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Hi Yves,
does somebody knows how those power TWTs evacuate heat ? By radiation of course :-) Not much chance for any other cooling method in vacuum. Tom -- When in doubt, use brute force. - Ken Thompson |
#2
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Vacuum tubes in vacuum
Dreaming ....
I've heard that some Broadcast TV satelites use TWT as power amplifiers. Do they have a hermetically sealed envelope As a reference to the LOOOOOOOOOONG thread about plate color and how they radiate heat in vacuum, does somebody knows how those power TWTs evacuate heat ? Wondering .... Yves. |
#3
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The TWTs generally are radiation cooled. Meaning that the collectors (where
most of the heat is dissipated) have large fins that radiate the heat to space. Most space TWTs are this way. Some, however, are conduction cooled to the mounting surface (referred to as the 'panel') and that heat is dissipated elsewhere, the heat being transferred away from the TWTs with heat pipes underneath and integral to the panel. All the TWTs, radiation cooled or conduction cooled, have such heat pipes below them. "Yves Monmagnon" wrote in message ... Dreaming .... I've heard that some Broadcast TV satelites use TWT as power amplifiers. Do they have a hermetically sealed envelope As a reference to the LOOOOOOOOOONG thread about plate color and how they radiate heat in vacuum, does somebody knows how those power TWTs evacuate heat ? Wondering .... Yves. |
#4
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Hi Patrick,
I think Yves talked about transmitting tubes in satellites. No air stream or water flow to cool them in space ... only radiation cooling is available out there. Surly there are internal cooling systems like heat pipes leading the heat power from the point the heat origins from (e.g power tube plates, or the nuclear reactor "batteries" often found in military satellites) to the radiation cooling fins at the outside of the satellite, but in the end it is all pure radiation cooling to get the heat power away from the satellite structure/body. And with water cooling, the tubes could be small, and no trouble for 500 watts of dissipation. As far as I know, HAMs sometimes put generic RF output stage tubes "upside down" into oil baths and run them _way_ beyond their nominal "air cooled" dissipation. Together with intermittend CW morse/pulse operation they draw power ratings from a 6L6 (or what else they use) which would make us AF types simply _faint_. Probably HAMs lurking here due to the AM radio thread can elaborate a bit ... Tom "hurrying to order a 1cbm tank full of SF6 at -20C to drown my ECL82PSET in which surely will be good for 1,5 KW sustained AF power then ;-)" P.S.: Don't try liquid nitrogen, the temperature gradient in operation would be too steep for the glas envelope ... -- A gleekzorp without a tornpee is like a quap without a fertsneet (sort of). |
#5
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Tom Schlangen wrote: Hi Patrick, I think Yves talked about transmitting tubes in satellites. No air stream or water flow to cool them in space ... only radiation cooling is available out there. I wasn't sure what TWT stood for. I live down hera on terra firma, and my mind and amps don't have to survive space. Water cooling would still work up there if there was someplace cool to radiate the heat out from a large heat exchanging panel, say from the shady side of a space craft They say you get a suntan easy when you work outside repainting the weather boards of the space station. Surly there are internal cooling systems like heat pipes leading the heat power from the point the heat origins from (e.g power tube plates, or the nuclear reactor "batteries" often found in military satellites) to the radiation cooling fins at the outside of the satellite, but in the end it is all pure radiation cooling to get the heat power away from the satellite structure/body. Exactly.... And with water cooling, the tubes could be small, and no trouble for 500 watts of dissipation. As far as I know, HAMs sometimes put generic RF output stage tubes "upside down" into oil baths and run them _way_ beyond their nominal "air cooled" dissipation. Together with intermittend CW morse/pulse operation they draw power ratings from a 6L6 (or what else they use) which would make us AF types simply _faint_. Indeed, ony could simply lower the whole amp into an oil bath, and the insulation is improved as well. But the plate inside a glass vacuum tube would still get very hot. The ability to produce say 300 watts of power from a pair of EL36/6CM5 is assisted by the use of class C. Probably HAMs lurking here due to the AM radio thread can elaborate a bit ... Tom "hurrying to order a 1cbm tank full of SF6 at -20C to drown my ECL82PSET in which surely will be good for 1,5 KW sustained AF power then ;-)" P.S.: Don't try liquid nitrogen, the temperature gradient in operation would be too steep for the glas envelope ... But at least the wires would have low resistance, and imagine the sound quality, with super cooling. Liquid helium might be better. Patrick Turner. -- A gleekzorp without a tornpee is like a quap without a fertsneet (sort of). |
#6
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TWT - Travelling Wave Tube.
Invented by Rudolph Kompfner, an Austrian who was interned in Britain during the early part of WW II. He was released to work on the TWT for the British Admiralty during the later years of the war. Eventually he came to the U.S. and worked on other developments at Bell Labs with J.R. Pierce. Dr. Pierce at Bell Labs had taken the TWT beyond Kompfner's original design. The Pierce gun, a converging beam design, is the heart of all TWTs. All this was in the late 40s. "Patrick Turner" wrote in message ... Tom Schlangen wrote: Hi Patrick, I think Yves talked about transmitting tubes in satellites. No air stream or water flow to cool them in space ... only radiation cooling is available out there. I wasn't sure what TWT stood for. I live down hera on terra firma, and my mind and amps don't have to survive space. Water cooling would still work up there if there was someplace cool to radiate the heat out from a large heat exchanging panel, say from the shady side of a space craft They say you get a suntan easy when you work outside repainting the weather boards of the space station. Surly there are internal cooling systems like heat pipes leading the heat power from the point the heat origins from (e.g power tube plates, or the nuclear reactor "batteries" often found in military satellites) to the radiation cooling fins at the outside of the satellite, but in the end it is all pure radiation cooling to get the heat power away from the satellite structure/body. Exactly.... And with water cooling, the tubes could be small, and no trouble for 500 watts of dissipation. As far as I know, HAMs sometimes put generic RF output stage tubes "upside down" into oil baths and run them _way_ beyond their nominal "air cooled" dissipation. Together with intermittend CW morse/pulse operation they draw power ratings from a 6L6 (or what else they use) which would make us AF types simply _faint_. Indeed, ony could simply lower the whole amp into an oil bath, and the insulation is improved as well. But the plate inside a glass vacuum tube would still get very hot. The ability to produce say 300 watts of power from a pair of EL36/6CM5 is assisted by the use of class C. Probably HAMs lurking here due to the AM radio thread can elaborate a bit ... Tom "hurrying to order a 1cbm tank full of SF6 at -20C to drown my ECL82PSET in which surely will be good for 1,5 KW sustained AF power then ;-)" P.S.: Don't try liquid nitrogen, the temperature gradient in operation would be too steep for the glas envelope ... But at least the wires would have low resistance, and imagine the sound quality, with super cooling. Liquid helium might be better. Patrick Turner. -- A gleekzorp without a tornpee is like a quap without a fertsneet (sort of). |
#7
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wrote in message
.com... TWT - Travelling Wave Tube. I thought it was a Travelling Wave Amplifier Tube? Tim -- In the immortal words of Ned Flanders: "No foot longs!" Website @ http://webpages.charter.net/dawill/tmoranwms |
#8
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Nope. Travelling Wave Tube - TWT. That is the tube alone. When connected
to a power supply and attached to the system, the combination of tube and power supply can be referred to as a TWTA - Travelling Wave Tube Amplifier. "Tim Williams" wrote in message ... wrote in message .com... TWT - Travelling Wave Tube. I thought it was a Travelling Wave Amplifier Tube? Tim -- In the immortal words of Ned Flanders: "No foot longs!" Website @ http://webpages.charter.net/dawill/tmoranwms |
#9
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My dad used to run a pair of 807s in push-pull at 150W in this manner
(with them suspended in an oil bath). Worked great until the bath leaked out, then his set fried! Joe Tom Schlangen wrote in message ... Hi Patrick, I think Yves talked about transmitting tubes in satellites. No air stream or water flow to cool them in space ... only radiation cooling is available out there. Surly there are internal cooling systems like heat pipes leading the heat power from the point the heat origins from (e.g power tube plates, or the nuclear reactor "batteries" often found in military satellites) to the radiation cooling fins at the outside of the satellite, but in the end it is all pure radiation cooling to get the heat power away from the satellite structure/body. And with water cooling, the tubes could be small, and no trouble for 500 watts of dissipation. As far as I know, HAMs sometimes put generic RF output stage tubes "upside down" into oil baths and run them _way_ beyond their nominal "air cooled" dissipation. Together with intermittend CW morse/pulse operation they draw power ratings from a 6L6 (or what else they use) which would make us AF types simply _faint_. Probably HAMs lurking here due to the AM radio thread can elaborate a bit ... Tom "hurrying to order a 1cbm tank full of SF6 at -20C to drown my ECL82PSET in which surely will be good for 1,5 KW sustained AF power then ;-)" P.S.: Don't try liquid nitrogen, the temperature gradient in operation would be too steep for the glas envelope ... |
#10
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Fred Nachbaur wrote in
: Tim Williams wrote: wrote in message .com... Nope. Travelling Wave Tube - TWT. I thought it was a Travelling Wave Amplifier Tube? It was a joke.. put it back in acronym form.. ) Tim Like the one about the Trans-World Airlines stewardess who asked her business passengers, "Sir, would you like some TWA coffee, some TWA milk, or some TWA tea?" Cheers, Fred Then there is the Fast Asynchonous Receiver-Transmitter. I cannot remember who made it. r -- "Any sufficiently advanced technology is indistinguishable from magic." Arthur C. Clarke (1917 - ), "Technology and the Future" |
#11
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Rich Andrews wrote: Fred Nachbaur wrote in : Tim Williams wrote: wrote in message igy.com... Nope. Travelling Wave Tube - TWT. I thought it was a Travelling Wave Amplifier Tube? It was a joke.. put it back in acronym form.. ) Tim Like the one about the Trans-World Airlines stewardess who asked her business passengers, "Sir, would you like some TWA coffee, some TWA milk, or some TWA tea?" Cheers, Fred Then there is the Fast Asynchonous Receiver-Transmitter. I cannot remember who made it. Wasn't that design prone to "motorboating"? Cheers, Fred -- +--------------------------------------------+ | Music: http://www3.telus.net/dogstarmusic/ | | Projects: http://dogstar.dantimax.dk | +--------------------------------------------+ |
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