A ton of great work is still being done in the tube industry despite almost no governmental funding. For a great article on the subject check out, "TWTs Still Drive High Power Systems" by Meppalli Shandas (in July 2009 Microwaves & RF issue). A copy of the article is available at: http://www.dbcontrol.com/assets/pdfs/dB-Control-July-MWRF-TWTs-Still-Drive.pdf

What industry isn't in serious decline?

I have to agree that there are just some performance hurdles that solid state systems will never overcome. Everyone has this newer is better mentality and the idea that it is old so it must be replaced. Case in point The FAA's Decommissioning of the ARSR 1 and 2 sites to replace them with solid state systems that provide much less coverage and will rely on aircraft transponders and GPS for aircraft position both of which can be circumvented. The idea we need multi-megawatt output for a skin paint is so old school but it worked for better than 60 years.

I'm curious, apart from warming my dinner - what are MW of GHz used for?

Was expecting a longer, more detailed article.No one mentioned the Cross-Field Ammplifer tube as a high power, high efficiency microwave amplifier. I have had the same question as to how Solid State was ever going to get up to the Megawatt powers, or even high kilowatts at X and K bands, as well as S band/

BTW there's an S band magnetron in every kitchen. Don't expect that to go solid state any time soon.

Maybe I missed some link but when I select "Read the Full Article" I expect more than 2 paragraphs......

As for the content, as someone said, there is nothing new, though some of the comments are interesting. Your application should drive you to the best solution, tube or solid state.

Nothing new here: High frequency + small chip size = KWatts/square mm with high resistive and dielectric losses. Tubes: A near vacuum has no resistive losses and Tan delta starts with several zeroes after the decimal point. Think back to ~1980: Dexcel developed Octave bands at +23 to +26dBm to 18GHz - very expensive and the ones we bought did not last. Never heard of Dexcel again. No really significant performance gains since.

Wow, SOme one else from the "old" days in EW. Airborne pods, under the wings of a Phantom II or an F105. Brings back reminders of popped hard line.

pfb

Worked in very long range tracking radars, klystrons and TWT are still the only able to provide you the perfs you need. Would add that cold cathode tubes are a very promising technology. Ghislain

Hell would freeze over before solid state devices could produce megawatts of power at X or millimeter band frequencies, and the whole of frozen hell would be needed as a heat sink!

They do have solid state high power amps; they have to phase combine signals to get the power. They consume a lot less power; use 24VDC; and you dont need dangerous high voltages. Also; the switching power supplies for the high voltages for the TWTs are noisey as hell. Im all for continuing the development to get rid of TWTs. If you ever worked on those; you know that even a pin hole in the wires; sticking your hands in there can reach out and get you. I was so stressed out working with those; hoping I wouldnt get zapped.

Billions if not hundreds of billions of dollars have been completely wasted developing solid state systems that are low gain, inefficient, impossible to properly cool, and thereby highly unreliable. It's about time the government and OEMs got back to the reality that the high reliability and outstanding performance of TWTs, Klystrons, and Gyrotons must be used for high pwer applciations. Too many years of horribly wasted development and manufacturing funding must be redirected to vacuum electronic devices before there is a complete melt down of these very important US industrial capabilities now in serious decline.

Gee it is great to see TWT,s are still in vogue, takes me back to my time in the navy where TWT's were used in electronic counter measure equipment. Might have to go back and revisit the fundamentals that I haven't thought about for 40 years or so.