Any issues in switching modules in /out ...
simply a multi primary transformer ?
Why not keep it simple, and do it like the Decca transmitters?
Forget complicated splitters/combiners with messy deliberate
isolation. You are combining identical signals so that sort of design is
not required.
BEFORE any low pass filters, take each output of each transmitter module to
separate identical primary windings on one, normal ferrite transformer
core. Use a single secondary to take the combined power off through a low
pass filter to your antenna. (But do size the core and turns for
the TOTAL power to be generated)
As both transmitter modules will be delivering identical outputs, the
voltage induced in primary 2 coil from Tx module 1 will be exactly equal to the
that delivered to it from Tx module 2 (and vice versa) so with both
transmitters operating correctly, the outputs will sum in the secondary.
you are adding teh currents delivered by each stage, from an equal voltage
delivered by both. You are, to all intents and purposes, connecting the
transmitters in parallel to multiply the current delivered in total
You can use the combining transformer for impedance matching if wanted -
for example the Decca ones have direct drive to the primary windings via a
tank circuit and each of the ( In their case three) primary to single-secondary
turns ration ratio sets the impedance transformation.
Isolating combiners like Wilkinsons only come into their own properly when
non-identical signals need to be summed while keeping the two sources isolated.
Intermod testing in receivers is a particular case in point, where
the two test signals have to be summed without generating their own intermod
products caused by the output of one source leaking into the (probably
non-linear) output of the other. If that happened, self-generated IMPS
that could swamp those being tested-for.
Andy G4JNT
