Easier cross-neutralisation has been mentioned, but another major argument for
push-pull,
especially at higher frequencies, is that it becomes easier to get the proper
L/C ratio
as the circuit tuning and stray capacitances essentially are in series.
73/
Karl-Arne
SM0AOM
----Ursprungligt meddelande----
Från : k2vco.vic@gmail.com
Datum : 2020-08-01 - 20:08 (CEST)
Till : amps@contesting.com
Ämne : Re: [Amps] Push pull amps
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
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|