In message , Ralph
Mowery writes

"Ian Jackson" The usual basic
circuit is:
Input port to ground - a 2:1 impedance ratio step-down ferrite-cored
autotransformer T1 to ground.
T1 tap is connected to the centre tap of a second 1:1 ratio ferrite-cored
autotransformer T2.
Each end of T2 of connected to each output port.
A 100* ohm resistor R is connected between the ends of T2 (ie between the
output ports).
*R is 2 x Zo, so for a 75 ohm system, it will be 150 ohms. Note the
purpose of T2 and R is to provide isolation between the outputs (for
signals coming back into the output ports).

Now we are getting somewhere. The circuit you describe is differant from
any that I have seen in my very short search for combiners. With nothing
but transformers in the circuit I can see where the losses would only be
part of a DB or so. Much differant than the combiners that I saw using
either resistors or combinations of resistors and a single core
'transformer'.

This circuit is used in 1001 makes of wideband FM/TV splitters
(typically 5 to 900+MHz) and even in satellite IF splitters up to
2100MHz. It is also widely used for combining signals on different
frequencies (where the loss is indeed 3-plus-some dB). However, while it
CAN be used for combining co-phased antennas, it's more usual to use
transmission lines (as have been described). Note that the small
ferrite-cored transformers are completely suitable for putting any real
RF power into, but transmission lines don't have this problem.
--
Ian