Hello Rik
Ferrite (as opposed to iron powder) is best for power transformation on LF
because of its high permeability, fewer turns = less copper loss. Iron powder
is better for resonant circuits and filters because of higher flux saturation
point
and it has better inductance stability and low loss / high Q.
The best material for 136 kHz transformers, as far as I know, is Philips 3F3
which has approximately half the core loss compared to 3C85, and 3C85 is
good! SM6PXJ and I used a 58mm 3C85 toroid as auto transformer for
antenna matching on our 7S6SAJ expedition. The antenna resistance was
7..8 ohms (most of this was radiation resistance! :o) and the transformer was
only slightly warm to the touch after running QRSS with about 1 kW output
from Christers TX. Just a couple of watts lost, I would guess. The winding was
made with 2.5 sq.mm flat wire (not Litz).
I have Philips ferrite data sheets in pdf format that I can send if you are
interested.
Attached picture shows the transformer in action at 7S6SAJ. Note the full scale
deflection on the 10A thermocouple "ammeter" in the icecream container.
Christer checked the meter later and found that 10A indicated was actually
12A RF... (photo by SM6PXJ)
73 de Johan SM6LKM
I am trying to make a list of toroid core material that is suitable for
136kHz power applications, for impedance transformers and low-pass filters.
I would appreciate any information about the material (brand-type), the
application (transformer or filter) and the power level it was used/tested.
many thanks in advance,
73, Rik ON7YD
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