It is not uncommon that ham designs for Sontheimer coupers (aka Tandem coupler, Grebenkemper coupler) fall short in the design of the magnetic components resulting in one or both of:
- high InsertionVSWR; and
- high core loss.
The above circuit is from (Grebenkemper 1987) and is an embodiment of (Sontheimer 1966). In their various forms, this family of couplers have one or sometimes two transformers with their primary in shunt with the through line. Let’s focus on transformer T2. It samples the though line RF voltage, and its magnetising impedance and transformed load appear in shunt with the through line. T2’s load is usually insignificant, but its magnetising impedance is significant and is often a cause of: Continue reading Sontheimer coupler – transformer issues