Thanks, Jim. Ed K6UUZ
On Tue, 2 Aug 2005 20:07:29 -0700 (PDT) Jim Candela <[EMAIL PROTECTED]> writes: > > Ed, > > I always admire those about to undertake such a > project. I don't have a circuit for you, but I will > share a few ideas. If you do use grid driven, it will > likely need to be class AB1 (zero drive power to tube, > i.e, just voltage), or class Ab2 where the grid draws > a little grid current on modulation peaks. In either > case, 25 watts will be way too much. Given the above > choices, I'd use Ab1, and a passive 50 ohm grid input > resistor, and scale the drive just short of grid > current. Still you will need a grid bias supply, and > screen supply in addition to a plate supply. That is a > lot of stuff, but hey, why not if you want to do it? > > Another approach, and I'm being a little simplistic > here, is to think of a 4-400 in grounded grid as > something similar to or about 4/5 a 3-500Z. A Heath > SB-220 does legal limit AM with under 25 watts > (carrier) of drive with two 3-500Z's in parallel G-G. > No screen supply needed, and bias if necessary is easy > with a power zener diode. So a 4-400 configured as a > GG linear should be good for 150 to 200 watts am > carrier output, and only need 10-15 watts carrier for > drive. My figures are a SWAG, but I'd bet they are in > the ballpark. > > Thanks for reading, > Jim Candela > WD5JKO > --- [EMAIL PROTECTED] wrote: > > > I am planning to build a linear amp around a grid > > driven 4-400 tube. Can > > anyone suggest where I can find a suitable circuit > > with component values. > > I would like band-switching for 80, 40 and 20 > > meters. I will be driving > > it with a 25 watt carrier output rice box on AM. I > > don't like the one in > > the ARRL 1967 handbook because it requires you to > > open the lid and > > physically change taps on the coil and change tuning > > capacitors. I don't > > have any other older handbooks. Thank you. > > > > Ed K6UUZ > > > ________ > > AMRadio mailing list > > Home: > > http://mailman.qth.net/mailman/listinfo/amradio > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:[email protected] > > > > ______________________________________________________________ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > >
