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Balun/Unun 1/9 ==> 50/450 Ohms.

Updated: Mar 7

FT240-31, FT240-43, FT240-61 and FT240-77



Used material: FT240-31


Start version Tuned version for best SWR

(move the coils for best SWR)


Used material: FT240-43


Start version Tuned version for best SWR

(move the coils for best SWR)


Used material: FT240-61


Start version Tuned version for best SWR

(move the coils for best SWR)

Used material: FT240-77


Start version Tuned version for best SWR

(move the coils for best SWR)



Schematic:


Primary (left):

1 coil with 9 turns = 9 turns.

Secundary (right):

3 coils with 9 turns and = 27 turns.

Impedance primary (50 Ohms) is 9 x 9 = 81


Impedance secundary 27 x 27 = 729

Calculated impedance secundary =

(50 Ohms/81) x 729 = 450 Ohms.



FT240-31 FT240-43


FT240-61 FT240-77


FT240-31 FT240-43


FT240-61 FT240-77



This SWR / return loss result is due to tuning of the coils as shown in the picture above.



FT240-31


FT240-43


FT240-61


FT240-77



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