In many years of RF transformers design and testing, it never occurred to me
a single combiner, or impedance transformer, performing like it should out
of the range of few octaves.
With some (heavy) compromise in performances, like wrong impedance
transformation, losses, poor directionality and so on, it's possble to talk
about devices "working" somehow into a maximum of 10 -12 octaves.
Actually, the limited core material properties and parasitic capacitances,
sign that a conventional broadband TV type hybrid coupler can't work well
at MF or at the low edge of SW.
If some of that devices does the job, it's only the result of a wrong design
for the VHF and UHF bands.
73,
Mauri I4JMY
i4jmy@iol.it
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