On Friday 19 January 2007 10:33, Larry Finger wrote: >Gene Heskett wrote: >> So I've noted, Larry. Are you offering snapshots packed as tar.gz's >> from time to time, something I can just nuke the existing kernel stuff >> and replace that whole subdir with your's? > >Usually, I offer patches for kernel versions from 2.6.18 forward to > incorporate the latest revisions. That is what I'm doing to keep the > openSUSE-released kernel (2.6.18.2) working on my laptop. I usually run > 2.6.20-rcX or wireless-2.6, but the "official" kernel of my distro is > always available. The patches are always available on my ftp server. > >> That could tempt me to try making a kernel for that lappy. >> >> But not till after I get this transmitter combo hooked up and actually >> running at WDTV-5. Our 50 year old GE tx uses 2 pairs of 4-1000 >> tubes, and I have the last tubes on the planet in that transmitter now >> and they are fading. So we've bought a newer Harris I'm going to use >> for a driver since its too small to make full power. I won't have a >> lot of breathing room till at least a month on down the log. Maybe >> longer what with needing to build the control interfaces from scratch >> too. > >That brings a thought to mind. What does any multi-kilowatt transmitter > use for output devices? Obviously, you cannot just use a solid-state > device.
Chuckle, yes you can, but the method does take many of the available output devices, usually a power fet type, and the combiner networks are 2/3rds of the weight of the whole transmitter. But yes, I can buy, from Larcan for instance, all solid stage transmitters at vhf power levels up to 50kw. An individual device failure costs the output of 2 of them because of the combiner physics, but the failure is what we call gracefull in that you are still on the air, and at full power until quite a few devices have failed. Oh, bring money too, this is 6 digit stuff and the first one is probably more than 3 these days... In our case, the final is a glass triode originally made by Eimac but now they are all being rebuilt from time to time by people such as Econco. Its a water cooled anode tube, with about 40 gallons of water a minute being pumped through it, then out to a big fan cooled radiator and dumped back into about a 200 gallon copper tank that the 10 horse pump pulls from. The fan is quad of torrington wheels about 16" in diameter & 9" or so deep on each side, keeping a 15 horse motor around nameplate current per phase. So in the end we move a lot of air. And we keep the water very pure because pure water is an insulator, those 1" id hoses that hook to the bottom of the socket have 7200 volts on them. We intercept the hoses before they hit grounded stuff so we can read the leakage & know when to change the deionizer cartridge, typically reading less than 1 milliamp, we change the cartridge when it gets up to 2 mills. Even so we change the hose barbs and hoses every so often because the hose barbs are corroded away inside the hose where you can't see them. Blowing a hose off whats left of a hose barb makes a mess & takes quite a bit of drying. This tube weighs about 30 lbs, 20 of which is the copper anode and water jacket, stands about 28" tall, 10" maximum diameter for the grid contact ring which is at rf ground, but about -275 volts of bias. Operated as a grounded grid stage, the driver power (about 3 to 4 kw) we feed in not only drives the tube, but also comes out as output, that's the nature of grounded grid amplifiers. The tube itself is rated to 75kw 6 mhz wide in the low vhf band. We only need 27kw sync tip peak, so I don't run the heaters at full power which would be at 12 volts and 180 amps current. Overbuilt for the job, the last one ran for a bit over 10 years. It costs us in the area of $7k to get one rebuilt. This is the visual, the aural is actually a separate transmitter that due to the physics of 'intercarrier sound' has been running at about 900 watts for the last 12 years, its sufficient. I think the visuao tube we have in now will handily finish out the ntsc days which are scheduled to be turned off January 2009 now, only 2 years hence. But stay tuned, the dems are now in power and we're hearing rumors of yet another extension, so we're starting to arrange to get one of our duds rebuilt just in case. By now we're what I think could be called off topic though. The power level of this "radio" is about 10ee+07 of what a bcm43xx can do. :-) >Larry > >> Thanks. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Yahoo.com and AOL/TW attorneys please note, additions to the above message by Gene Heskett are: Copyright 2007 by Maurice Eugene Heskett, all rights reserved. _______________________________________________ Bcm43xx-dev mailing list Bcm43xx-dev@lists.berlios.de https://lists.berlios.de/mailman/listinfo/bcm43xx-dev
