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  • Writer's picturextgaby

Case study, how many turns are needed?

Updated: Sep 10, 2020

Picture Schematics

Number of turns left = number of turns right.

L value: XL value @ 1 MHz

1 turn: 0,02 mH 125 Ohms

2 turns: 0,06 mH 377 Ohms

3 turns: 0,17 mH 1.068 Ohms

4 turns: 0,32 mH 2.010 Ohms

SWR 1 turn

SWR 2 turns

SWR 3 turns

SWR 4 turns

Conclusion: More turns result in a better return loss at low frequencies

More turns result in a worse return loss at high frequencies

For return loss 2 turns looks the best of both worlds.

Insertion loss 1 turn

Insertion loss 2 turns

Insertion loss 3 turns

Insertion loss 4 turns

Conclusion: More turns result in a better insertion loss at low frequencies

2 and 3 turns gives the best results for insertion loss at high frequencies

3 turns gives the best result at low and high frequencies.

Smith chart 1 turn

Smith chart 2 turns

Smith chart 3 turns

Smith chart 4 turns

Conclusion: Also here it is clearly visible that 2 turns have the flattest swr curve.


At 15 MHz 2 turn showed an impedance of 45 ohms + j9 ohms.

See below, with 45 pF we can compensate the inductive behaviour.

I have used 39 pf (closest value in my junk box)

Picture Schematics

The results are truly fantastic:

Return loss:

Insertion loss:

Smith diagram:

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