[AMPS] YU181 idea

John T. M. Lyles jtml@lanl.gov
Wed, 29 Sep 1999 10:04:38 -0600


I agree, class C for CW is fine, or D or E. Use a suitable network 
for harmonic attenuation of course. And C should make QSK fine, as 
remove drive, the amp quits amplifying. But you need to drive it 
harder. Also the input network will have to be suitable to make the 
input look like a reasonable load for a solid state exciter, over the 
full cycle of RF.


At 11:45 PM -0400 9/28/99, Amps Digest wrote:
>Date: Tue, 28 Sep 1999 13:41:14 -0600
>From: Chip Owens <owens@atd.ucar.edu>
>Subject: [AMPS] Amplifier for cw only-question.
>
>If one uses an hf power amplifier for cw operation only is there any
>good reason to operate it in AB1, AB2, or class B? Wouldn't class C
>operation yield higher efficiency and actually make QSK operation
>easier to implement?

>Also, I'm curious if anyone out there is using the 3CX1200Z7/YU-181 in
>a homebrew amplifier. With its grid terminal brought out to a large
>circular flange on the tube base it would make an essentially zero
>impedance grid-to-ground connection. The data sheet mentions use of the

The generalization that a grid flange would make 'essentially' zero 
impedance from grid to ground is probably acceptable at low HF 
frequencies, but don't forget that there is a length from the flange 
up into the grid element itself. It certainly beats using a socket 
and bringing the grid out in a ring or pin to ground that way. At 
VHF, however, even the best of grounds on a grid is limited by the 
tube internal L to the elements. Hence, there is no such thing as an 
unconditionally stable tube. Thats my 2 cents worth,

John
K5PRO


>SK-410 socket, but no chimney is mentioned. Is this series of tubes,the
>3CX1200A7, 3CX1200D7, and 3CX1200Z7 a good choice for a homebrew amp
>over something like an 8877?
>
>This is my first posting to the reflector. Do I need to put on my
>flak-jacket before reading replies?

Did you?


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