TWT's are still widely used for satellite uplinks ... a typical broadcast uplink will be a pair of 400W tubes at around 14GHz .. one running to the antenna, one running to a dummy load, ready for instant changeover. The bigger tubes will run 750W.. There are no affordable solid state devices at those power levels at those frequencies. Surplus TWT's occasionally appear on the surplus market.
They are also highly prized by radio amateurs for "moonbounce" .. the path losses involved in bouncing a signal off the moon to another station are "significant" ... you generally want all the power you can get. The moon is quite far away and oddly enough, spheres of dust and rock with a fairly random surface are not exactly great reflectors ... On Tue, 19 Mar 2024 at 21:49, Dave Matthews <n36...@gmail.com> wrote: > We had some training on traveling wave amplifier tubes, referred to as TWAT > tubes back in Nike Hercules tech school in 1977. > > Dave > ex MOS 22L > > On Tue, Mar 19, 2024 at 4:35 PM gene heskett <ghesk...@shentel.net> wrote: > > > On 3/19/24 14:15, Robin Szemeti via Emc-users wrote: > > > I purchased a couple of large travelling wave tube amplifiers in an > > > auction. I phoned the US company to ask about schematics and a manual > > ... > > > "can we have the serial numbers please?" ... "sure ... " "great and > what > > > date did you sign the ITAR agreement?" <click brrrrr...> > > > > > I presume they've been disposed of in unsalvagable condition... Like if > > glass, smashed into small pieces by a 16 lb sledge. If they ever trace > > them to you, pix of the destruction may help. But not if ceramic body's > > instead of glass. Any dust from destroying them is lung cancer seed. > > Very 100% dangerous. Do not break, grind or file. > > > > And that auction has been advised of its illegality. It is a tech > > similar to klystrons but with a more distrituted and much broader band > > applications that because of ITAR has faded away into a technical info > > vacuum. I've not heard of a twt since the cold war warmed up in the late > > 50's and we started building ICBM's in everybody's back yard. I was > > there, help build 3 titan ones in the middle of nowhere South Dakota. > > > > > On Mon, 18 Mar 2024 at 17:45, gene heskett <ghesk...@shentel.net> > wrote: > > > > > >> On 3/18/24 11:28, Todd Zuercher via Emc-users wrote: > > >>> Gene, > > >>> > > >> Well 2 things I've observed since posting that, Todd. the pix is > > >> identical for a 3 kilohertz version on amazon for about the same > price, > > >> once adjusted to us dollars . So I'm wondering if aliexpress added an > > >> extra 0, they rarely know what they are selling anyway. > > >> > > >> And since it showed up on amazon too, I'm wondering if the ITAR rules > > >> have been relaxed. > > >> > > >> Here is the highest HP rated amazon offering. 15kw 20hp for about > $1200: > > >> < > > >> > > > https://www.amazon.com/Mollom-220V-15KW-20HP-Frequency/dp/B0CQBZ4FZN/ref=sr_1_52?crid=30GVV1U3R7JUA&dib=eyJ2IjoiMSJ9.5mKofR2CvOgdLO3tCtLjmKysBbvC8T8oTt4SNyV7-PqBQ6UsvOrsvyppX7rBUpjT2IZZ2mAWKRkL0H1nJj5MGcPBTDsP2EbqZePAsB09iFXxVTemY7Dr4c-fOZHZLdaaBQulJLMrOYJl5bQBZyyubX0LkNc-DuFlyrVam8hlnFXUx5O0mASax2WBIToQk1TnTgzTo9aSvbn0kcp1wxgKUbqJsSefz-wM0iZmaooVN5zTcqmgr8SzJWLCsHsviwy3aYCLB0dDN-JFW7Rw6Cp1GUTSqURhr6UCPywhkuSnYI0.1sKFN_5H6kH9Ju3mlK1mAlKX2LaJ6eM0Et-7LWB83CI&dib_tag=se&keywords=high+speed+high+horsepower+vfd&qid=1710778937&sprefix=high+speed+high+horsepower+vfd%2Caps%2C82&sr=8-52&ufe=app_do%3Aamzn1.fos.765d4786-5719-48b9-b588-eab9385652d5 > > >>> > > >> > > >> I'd think that could run your 4 pole motor at 800hz just fine. UNK and > > >> unstated in the adv is the control range so I would scale the 3k range > > >> so max from the controller would only get you the rated speed at the > > >> motor. But I don't have to tell you that, you've been dealing with > those > > >> sorts of problems with that machine for long enough this ought to be > the > > >> best answer. Sometimes this is self limiting, higher frequencys run > > >> into the motors inductance, coil current falls and the motor actually > > >> slows down, my Sheldons max usable speed while running a 70 yo motor > > >> that never saw a vfd until me is about 200 hz as the coil current is > > >> under an amp at 200 hz. 3.7 amps at 60 hz. OTOH it can run it at 5hz > > >> long enough to finish the job and still lay my hand on that motor w/o > > >> discomfort from the heat. > > >> > > >> As for needing a new one, the usual failure is going to be the line > > >> stage filter caps which often will have a note in the docs someplace > to > > >> the effect that they should be replaced at 5 year intervals, however > the > > >> smaller ones that don't have braking resistors are actually 4 quadrant > > >> controllers, meaning a quick reversal will overvolt those filters for > a > > >> few milliseconds as they do the reversal, they suck that power out of > > >> the motor stopping it, storing it as overvoltage in those filters, > then > > >> as soon as the new direction is applied use that stored energy to spin > > >> the motor back up in the other direction, so the overvoltage is not > > >> present long enough to damage them, but actually contributes to > > >> maintaining the "forming" of those caps so they live longer. The 1.5 > hp > > >> rated el-cheapo clone running the 1 hp in my Sheldon lathe is now > around > > >> 9 years old and can still reverse that motor and its 40lb 8" 4 jaw > chuck > > >> in under 1/3 second at 100 revs. Overshoot at 100 revs is .24 turns > from > > >> 100 rpm to stopped. And the shop lights don't blink. Its all in the > .hal > > >> file if interested. No circuit breakers in any danger of tripping as > all > > >> the excitement is in the vfd and doesn't involve the wall power. Just > > >> give me a yip. > > >> > > >> These aren't toy's, they can kill, so give them the respect such > killers > > >> deserve. But I don't have to tell YOU that. > > >> > > >> Take care & stay well Todd. > > >> > > >>> In all honesty I wouldn't mind knowing more about your VFD source you > > >> say you want black listed. I'm so sick of trying to track down high > > speed > > >> VFDs that I'm almost tempted to pay the machine manufacturer's > > ridiculous > > >> 3X normal retail list price markup the next time we need a new one. > We > > >> occasionally have needed a replacement VFD capable of running about a > > 15kw > > >> 4pole router spindle at up to 24krpm (that is 800hz output, most > drives > > >> seem to max out at or are limited to 500-600hz output.) The last time > > we > > >> tried to order a new drive with these specs it was put on back order > for > > >> more than 1 year before we canceled the order. (We canceled after the > > >> delivery date had been pushed back 3 months for the 5th time.) Then > we > > >> bought a used one off of ebay. (Tracking down a used drive on ebay > with > > >> documented proof of the correct high speed firmware, when the sellers > > have > > >> no clue, is also another annoying trick to perform.) > > >> > > >> That is what we get for doing unusual things Todd, Goes with the > > >> territory. The trick is getting the info needed to make an informed > > >> decision from someone who has NDI what those numbers represent. They > > >> simply don't speak the language. And it can be very frustrating. > > >>> > > >>> Todd Zuercher > > >>> P. Graham Dunn Inc. > > >>> 630 Henry Street > > >>> Dalton, Ohio 44618 > > >>> Phone: (330)828-2105ext. 2031 > > >> > > >> Cheers, Gene Heskett, CET. > > >> -- > > >> "There are four boxes to be used in defense of liberty: > > >> soap, ballot, jury, and ammo. Please use in that order." > > >> -Ed Howdershelt (Author, 1940) > > >> If we desire respect for the law, we must first make the law > > respectable. > > >> - Louis D. Brandeis > > >> > > >> > > >> > > >> _______________________________________________ > > >> Emc-users mailing list > > >> Emc-users@lists.sourceforge.net > > >> https://lists.sourceforge.net/lists/listinfo/emc-users > > >> > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > . > > > > Cheers, Gene Heskett, CET. > > -- > > "There are four boxes to be used in defense of liberty: > > soap, ballot, jury, and ammo. Please use in that order." > > -Ed Howdershelt (Author, 1940) > > If we desire respect for the law, we must first make the law respectable. > > - Louis D. Brandeis > > > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
