On Dec 31 2008, 7:16*pm, ken scharf
wrote:
K7ITM wrote:
On Dec 30, 2:54 pm, ken scharf wrote:
Tio Pedro wrote:
"ken scharf" wrote in message
. ..
* Even with it's 'hard vacuum' the 01 didn't have as good a 'getter' as
later tubes and would arc over with more than 130 volts or so. *It was
used as a transmitter before the type 202 tube became widely available,
but was a QRP thing, less than a watt input.
Will it have enough output to drive a 245?
I'm sure it will drive a neutralized 245 to provide some gain.
You might not get enough drive for full power output from the 245.
(even if the 245 was run in class A, which requires NO driving power
you would still see SOME power gain).

Hmmmm...You think class A at RF requires no driving power??

Cheers,
Tom

Only voltage, no current.
Of course some power gets wasted since resistance isn't zero and some
heat is generated in the coils, etc. *I guess there is some power factor
in the grid / cathode capacitance etc. *The input impedance of the '45
in class A SHOULD BE infinite. *It isn't, but it IS VERY HIGH. *So
except for losses, no driving power, only voltage.

OK, to get an _accurate_ answer with respect to grid driving power,
you need to account for the effects of the electrons going from
cathode to plate as they pass by the grid. At high enough frequency,
this becomes significant. This is quite apart from losses in elements
external to the tube. One reference about this is Terman's "Radio
Engineers' Handbook, section 4, paragraph 9. But just consider that
it takes a certain amount of _energy_ to push those electrons around
and control them, even if they don't actually ever come in contact
with the grid.

Cheers,
Tom