Just some simple questions. Why use an 813 for an amp. 125 watt plate dissipation, 50 watts of heater power, and a large physical size. The "modern" 572b uses 25 watts for heater power has 225 watts dissipation and is cheap. I have two SB200s they put out 800 watts PEP and they can be bought real inexpensive. Every couple of years I stick new tubes in them for kicks and use the pulls as spares or "presents".
I love building, but I am practical too. But have fun guys and please be careful. George, W6GF ________________________________ From: Ron D'Eau Claire <[email protected]> To: Sent: Wed, December 22, 2010 9:20:47 AM Subject: Re: [Elecraft] 100 Watts or 500 Watts Time to dig out some old ARRL Handbooks from the 60's. My '62 Handbook has a nice 813 grid driven amp that runs Class C for CW and AB2 for SSB, the famous "one band kilowatt" amplifiers using a pair of 813's (each band had its own RF 'deck' with a common power and metering circuit so each amp could be pre-tuned and ready to go at the snap of a relay or switch) and a Kilowatt grid-driven 4-400A amp, in addition to the usual assortment of ground grid amps. A builder today may need to 'beef up' the pi-network output filter to meet modern spurious emission standards (typically for the second harmonic) or use an outboard half-wave filter for each band for that purpose. Ron (radios should glow in the dark) AC7AC -----Original Message----- On 12/22/2010 11:30 AM, a lister wrote: Grounded-grid is not the only way to design a tube amplifier. Although a traditional grid-driven circuit is a little more complicated, it's one way to get more gain. Amen to that. When I was little, "grounded grid" was vaunted as the way to use triodes without needing neutralization, even though one took a real hit on gain. Unfortunately, the old-time big amps that use/used several triodes in parallel in grounded grid still have a tendency to "take off." The 813 and the various Eimac ceramic tetrodes are wonderful tubes, and if one can go high voltage low current, they are excellent performers. Again, when I was young, solid state devices wouldn't function in the VHF/UHF region, and the 4CXnnn series were practically a necessity. Need I refer to the beautiful amps vended by one of the early moonbounce guys? I for one would like to see designs using these tubes. Not all of us need linear/linearized amps. John Ragle -- W1ZI ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
