Push-pull is a nice method. The link below shows
a push-pull amp I built 59 years ago; it still runs
full power with the original Eimac tubes.
http://www.zianet.com/k5am/amp6mkw.html
73,
Mark, K5AM
On 2020-08-01 18:08, Victor Rosenthal 4X6GP wrote:
I think the main reason they liked putting triode amplifiers in
push-pull was to simplify the neutralization. Of course it is possible
to neutralize single-ended amps with a bridge circuit or to use
inductive neutralization, but I think it's easier to obtain complete
neutralization with a push-pull circuit.
The change came about with the popularity of tetrodes which are easy
to neutralize in single-ended configuration, the popularity of
pi-network output circuits, and the desire to get away from plug-in
coils (think about bandswitching a balanced tank circuit). Also, TVI
shielding was difficult with plug-in coils.
I think probably the change happened after WWII, when surplus coax
became available. Shielded, single-ended circuits with pi-networks
running into coax-fed antennas became the hot setup.
73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 01/08/2020 20:02, Tom Osborne Sr. wrote:
I recently purchased some QST's from '47, 49, and 50. I notice a lot of
transmitters and amps back then used 2 tubes in push-pull circuits,
instead
of parallel, like we mostly do now.
What was the idea behind push pull compared to parallel, and when did
the
change take place? Thanks and 73
Tom W7WHY
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