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The use of a line output transformer core to make a balun.

Updated: Apr 25


Be careful when removing the core as it is very fragile!


10 windings were made both top and bottom.

They behave like 100 ohm transmission lines.

Input parallel = 50 Ohms.

Output series = 200 Ohms.




Due to the good low frequency behavior and the capacitive behavior at high frequencies, I have decided to reduce the number of windings from 10 to 7.


2 x 10 turns 2 MHz 2 x 7 turns 2 MHz

Return loss 2 x 7 turns

SWR 2 x 7 turns




Insertion loss measuments:

Left: LOT core Right: FT240-43


Detail:



Total loss worst case = 0.4 dB @ 30 MHz

If we assume that both devices represent the same loss:

1 device represent 0.2 dB @ 30 MHz = 4.5 % power loss.














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