On Wed, 27 Jun 2012 22:06:46 -0500, John Byrns
wrote:
In article ,
flipper wrote:
For this application I tend to think of them as almost the same thing
but am beginning to realize that the 'extra' G4 screen is probably
what gives a heptode the higher plate impedance. Is that why, despite
the 'accidental' mentioning of dual control pentode, you seem to be
adamant about heptodes, or is there another reason?
The reason I am "adamant about heptodes", if that is what you want to call it,
is not because of the plate resistance, it is simply because I have no
familiarity at all with DC pentodes and their characteristics.
Oh, okay. Well, just saying you're not familiar with them was enough
I don't even know any DC Pentode type numbers and am not sophisticated enough to
know that the plate resistance of a DC pentode is lower than a heptode.
Assuming the plate resistance of a DC Pentode is lower than a heptode, is that a
bad thing?
Well, it affects plate tank Q.
6AS6, 6DT6, 6GY6, and 6888 are some of the more 'popular' ones for
broadcasters.
I am not "adamant about heptodes", in fact I don't particularly care for grid
modulation, preferring plate modulation instead, however it is hard to conceive
of how to build a plate modulated transmitter using only one single section
tube, leaving the heptode, or possibly the DC Pentode, as the only easy choice
for a single tube transmitter. I do have a design for a single tube transmitter
using your 6ME8 that meets my design brief, however it would require me to build
my own well balanced push-pull RF antenna coupling transformer.
Yeah, a PP transformer is in some of my designs too but I'm skittish
about trying to wind one.