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From: Tim Williams on 12 Feb 2010 11:51 "Spehro Pefhany" <speffSNIP(a)interlogDOTyou.knowwhat> wrote in message news:q42bn51nvjgoqf6eiemgtfnosrmoucb5p6(a)4ax.com... >>Y'think magnetrons will be around forever? > > Probably disappear about the same time as hard disk drives disappear. Hmm, interesting correlation. They are about as old. Figure another fifty years at least? ;-) Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: John Larkin on 12 Feb 2010 12:20 On Fri, 12 Feb 2010 10:48:46 -0600, "Tim Williams" <tmoranwms(a)charter.net> wrote: >"Tim Wescott" <tim(a)seemywebsite.com> wrote in message >news:0_CdnWT3Qt5s4OjWnZ2dnUVZ_jdi4p2d(a)web-ster.com... >> The packaging details make it very hard to keep stable -- the inner >> element's gain goes up to UHF or higher, and those wires start looking >> awfully inductive. AFAIK "pencil" tubes and lighthouse triodes were >> designed in large part to be a better mechanical fit to coaxial cavities. > >Don't forget nuvistors. :) > >And then there's these guys; >http://webpages.charter.net/dawill/Images/Raytheon%20RK-707B.jpg >although now we are actually talking electron drift and bunching. I've >always wondered if I could operate this thing as a planar tetrode though. >S'pose I should try some time. I don't have the equipment to detect >microwave oscillations if it misbehaves though. > >> Which is why tubes are still king for really high power VHF and microwave >> stuff. Uneasy on the throne, though. > >Y'think magnetrons will be around forever? > >GaN and etc. would have to get pretty damn cheap to offset them. > >Tim This is a great book, http://www.amazon.com/Inventor-Pilot-Russell-Sigurd-Varian/dp/0870152378/ref=sr_1_1?ie=UTF8&s=books&qid=1265994854&sr=1-1 written by Russel Varian's widow. All about California in the 1930s, early aviation, the invention of the klystron, and even has a villain, Frederick Terman. I see that new copies are going for $150. Mine is signed by Dorothy herself! John
From: VWWall on 12 Feb 2010 13:26 John Larkin wrote: > On Fri, 12 Feb 2010 00:16:00 -0600, "Tim Williams" > <tmoranwms(a)charter.net> wrote: > >> So? Light it up and get to work! Should be roughly comparable to a 2N5179, >> I'd guess. >> http://www.mif.pg.gda.pl/homepages/frank/sheets/049/9/955.pdf >> Plate resistance is slightly high and Gm noticably low, but capacitance is >> quite small and the plate curves look nice (mu and Rp are fairly constant in >> the operating range). Offhand, give it a ~20k plate resistor and you'll get >> around 7k || 1.4pF = 16.2MHz -3dB point if driven hard (not counting miller >> or probe C). Okay, I suppose a 2N5179 will switch faster than that, but in >> terms of fundamental performance, once it cuts off at fT, it doesn't really >> do anything anymore; with tubes, add some L to cancel the C and you'll get >> narrow-band performance for another decade or two. > > Tubes get killed, eventually, by transit time problems. There were > some lighthouse (planar) tubes with really tiny spacings that would > work at 3 GHz or some such. It took other tricks, like bunching, to > break that limit. > From an article on "Creative Thinking" by John R. Pierce: "Another example is provided by the development of the 416A triode. The original and startling germ of a creative idea was that after all these years a triode might still be the best amplifier for microwaves, if only the spacing were close enough and the grid fine enough. An auxiliary idea was that close enough spacings could be attained and held by grinding the cathode and a surrounding ceramic co-planar, and then supporting the grid from the ceramic. These were, however, mere germs of an idea. Something real and complete was brought into existence only after years of concentrated effort, including the inauguration of a program of cathode studies which is still being pursued for other purposes." I was at Bell Labs while this work was going on. I still have some tubes in conventional noval configuration that were used in doing the above cathode studies. Here's an interesting summary of some strange vacuum tubes: http://www.rfcafe.com/references/electrical/ims-2009-microwave-museum.htm -- Virg Wall, P.E.
From: Jim Thompson on 12 Feb 2010 14:00 On Fri, 12 Feb 2010 10:26:07 -0800, VWWall <vwall(a)large.invalid> wrote: >John Larkin wrote: >> On Fri, 12 Feb 2010 00:16:00 -0600, "Tim Williams" >> <tmoranwms(a)charter.net> wrote: >> >>> So? Light it up and get to work! Should be roughly comparable to a 2N5179, >>> I'd guess. >>> http://www.mif.pg.gda.pl/homepages/frank/sheets/049/9/955.pdf >>> Plate resistance is slightly high and Gm noticably low, but capacitance is >>> quite small and the plate curves look nice (mu and Rp are fairly constant in >>> the operating range). Offhand, give it a ~20k plate resistor and you'll get >>> around 7k || 1.4pF = 16.2MHz -3dB point if driven hard (not counting miller >>> or probe C). Okay, I suppose a 2N5179 will switch faster than that, but in >>> terms of fundamental performance, once it cuts off at fT, it doesn't really >>> do anything anymore; with tubes, add some L to cancel the C and you'll get >>> narrow-band performance for another decade or two. >> >> Tubes get killed, eventually, by transit time problems. There were >> some lighthouse (planar) tubes with really tiny spacings that would >> work at 3 GHz or some such. It took other tricks, like bunching, to >> break that limit. >> > From an article on "Creative Thinking" by John R. Pierce: > >"Another example is provided by the development of the 416A triode. The >original and startling germ of a creative idea was that after all these >years a triode might still be the best amplifier for microwaves, if only >the spacing were close enough and the grid fine enough. An auxiliary >idea was that close enough spacings could be attained and held by >grinding the cathode and a surrounding ceramic co-planar, and then >supporting the grid from the ceramic. These were, however, mere germs of >an idea. Something real and complete was brought into existence only >after years of concentrated effort, including the inauguration of a >program of cathode studies which is still being pursued for other purposes." > >I was at Bell Labs while this work was going on. I still have some >tubes in conventional noval configuration that were used in doing the >above cathode studies. > >Here's an interesting summary of some strange vacuum tubes: > >http://www.rfcafe.com/references/electrical/ims-2009-microwave-museum.htm Ah! The good old days when you could do your own glass work ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: John Larkin on 12 Feb 2010 15:05 On Fri, 12 Feb 2010 10:26:07 -0800, VWWall <vwall(a)large.invalid> wrote: >John Larkin wrote: >> On Fri, 12 Feb 2010 00:16:00 -0600, "Tim Williams" >> <tmoranwms(a)charter.net> wrote: >> >>> So? Light it up and get to work! Should be roughly comparable to a 2N5179, >>> I'd guess. >>> http://www.mif.pg.gda.pl/homepages/frank/sheets/049/9/955.pdf >>> Plate resistance is slightly high and Gm noticably low, but capacitance is >>> quite small and the plate curves look nice (mu and Rp are fairly constant in >>> the operating range). Offhand, give it a ~20k plate resistor and you'll get >>> around 7k || 1.4pF = 16.2MHz -3dB point if driven hard (not counting miller >>> or probe C). Okay, I suppose a 2N5179 will switch faster than that, but in >>> terms of fundamental performance, once it cuts off at fT, it doesn't really >>> do anything anymore; with tubes, add some L to cancel the C and you'll get >>> narrow-band performance for another decade or two. >> >> Tubes get killed, eventually, by transit time problems. There were >> some lighthouse (planar) tubes with really tiny spacings that would >> work at 3 GHz or some such. It took other tricks, like bunching, to >> break that limit. >> > From an article on "Creative Thinking" by John R. Pierce: > >"Another example is provided by the development of the 416A triode. The >original and startling germ of a creative idea was that after all these >years a triode might still be the best amplifier for microwaves, if only >the spacing were close enough and the grid fine enough. An auxiliary >idea was that close enough spacings could be attained and held by >grinding the cathode and a surrounding ceramic co-planar, and then >supporting the grid from the ceramic. These were, however, mere germs of >an idea. Something real and complete was brought into existence only >after years of concentrated effort, including the inauguration of a >program of cathode studies which is still being pursued for other purposes." > >I was at Bell Labs while this work was going on. I still have some >tubes in conventional noval configuration that were used in doing the >above cathode studies. > >Here's an interesting summary of some strange vacuum tubes: > >http://www.rfcafe.com/references/electrical/ims-2009-microwave-museum.htm Cool. I won a science fair prize, ca 1962, which was a trip to Bell Labs in Murray Hill. Being a poor kid from New Orleans, I had never flown before. Neither had I ever seen snow or rocks. They put us up at the Algonquin Hotel in Manhattan for the weekend (me and my high-school physics teacher) and then bussed us to Jersey. It was fabulous. Anechoic chambers, lectures on information theory, plasma jets, cool stuff. I saw what I think was the first LED, and had lunch with Walter Brattain. John
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