W6WRT comments interspersed below: I don't see an emoticon but I assume that was an attempt at humor. There never was such a requirement. Brand new Chinese 8877s are $550, but your point is taken. I'
ORIGINAL MESSAGE: REPLY: Are you talking control grid or screen grid? My understanding is that the control grid sees the same drive power whether grounded grid or grounded cathode operation. Incorrec
ORIGINAL MESSAGE: REPLY: GG can be any class. Which class it is depends on the bias voltage and drive level. 73, Bill W6WRT _______________________________________________ Amps mailing list Amps@cont
ORIGINAL MESSAGE: REPLY: GG does not require any more grid dissipation than grounded cathode. GG does require more driving power, but not for the grid. The extra driving power "modulates" the cathode
ORIGINAL MESSAGE: REPLY: Different issue. As you go from class A to AB1 to AB2 to B to C, both power output and efficiency increase. That's true for all tubes, not just the 4CX250. 73, Bill W6WRT ___
ORIGINAL MESSAGE: REPLY: That is true only if the tube is driven into the positive grid region. If the drive is kept below that point, the load is constant. In fact, the load is infinite - no drive p
ORIGINAL MESSAGE: REPLY: The difference is mostly semantics. A grounded grid amp where the grid(s) are connected directly to ground is definitely cathode driven. By comparison, a cathode driven amp m
ORIGINAL MESSAGE: REPLY: Yes but..... That approach allows all the energy from the filter caps to be dumped into the arc. We're trying to avoid that. 73, Bill W6WRT __________________________________
ORIGINAL MESSAGE: REPLY: More like shutting the gate after the first horse has gone through and preventing the rest of the herd from escaping. Having said that however, I am not a believer in the use
ORIGINAL MESSAGE: REPLY: Very poor advice. A far better method is to provide a resonant circuit in the input to provide a "flywheel" effect. And as I said before, even that is only needed if the tube
ORIGINAL MESSAGE: REPLY: The filter caps have two jobs: One is to filter out hum from the rectified DC and the other is to supply large amounts of energy during peak demand from the tube)s). I would
ORIGINAL MESSAGE: REPLY: I guess we will have to agree to disagree. In both circuits the drive is applied to the cathode (or filament). As long as the grid and screen are maintained at a steady DC le
ORIGINAL MESSAGE: REPLY: Apparently we are talking about different applications. The original discussion was how to avoid damage when the B+ arcs. In your post above you say " the filter cap(s) stay
ORIGINAL MESSAGE: REPLY: If Bill Orr is recommending a resistor to "swamp out" load variations over the RF cycle in a tube's input circuit, then yes, I disagree. A resistor can not store energy durin
ORIGINAL MESSAGE: REPLY: Nothing wrong with shutting off the PS quickly, but if you leave the filter caps charged, any damage from the B+ arc will involve much more energy than if the B+ line were op
ORIGINAL MESSAGE: REPLY: Ok, that should do it. 73, Bill W6WRT _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps
ORIGINAL MESSAGE: REPLY: All good points, especially the one quoted above. When I worked at Tektronix we tried to avoid the term "ground" and used "common" instead. In many circuits the common was el
ORIGINAL MESSAGE: REPLY: By using only the ALC in the transceiver, this is what you accomplish. That's how I do it. 73, Bill W6WRT _______________________________________________ Amps mailing list Am
ORIGINAL MESSAGE: REPLY: I'm curious - what would be the reason for using resistors and decoupling caps? 73, Bill W6WRT _______________________________________________ Amps mailing list Amps@contesti