Some 7 people have asked about more info about the 8877 Push-Pull (PP)
design. This was a commercial design for which the customer has retained all
the engineering right. As such I will not be able to give detail about this
project.
However we can discus about RF PP design in general :)
I find my self more comfortable with such a design as it is symmetrical and
elegant.
The Tubes are actually running at half the output power which keeps them
cool,
and perhaps more cheaper and/or available.
The output thank is transformer isolated and thus no danger of exploded
caps.
Second harmonic is inherently suppressed which makes all even spurs more
easily to handle. There are many more pluses for a PP design...
However, the EACM (Environment Automated Control & Monitor) is more
complicated and implies microprocessor control. You must deal with currents
thru two cathodes, grids and anodes and you must keep them balanced inspite
the aging of the components. One can say the art of a Tube Push-Pull Amp is
in the building a smart enough EACM more than in the RF deck. So... if you
are not comfortable with microprocessing, embedded programming and such, a
PP
might become a daunting task.
Alex, N2NNU
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