Remark: all return loss measurements (SWR) are with a light inductive load (adjustable resistor). Real results are always better then stated here.
Used core: FT240-31 Amidon.
4 wires 6 turns each
1 wire 4 turns.
Adjustable resistor of 100 Ohm adjust for minimum SWR, disconnect the resistor and measure the value with a multi meter.
Measured value was exact 68 Ohm as calculated value.
Schematic diagram:
Primary (left):
4 coils with 6 turns = 24 turns.
Secundary (right):
4 coils with 6 turns and 1 coil with 4 turns = 28 turns.
Impedance primary (50 Ohm) is 24 x 24 = 576
Impedance secundary 28 x 28 = 784
Calculated impedance secundary = (50/567) x 784 = 68 Ohm.
Used core: FT240-31 Amidon.
5 wires 5 turns each.
Adjustable resistor of 100 Ohm adjust for minimum SWR, disconnect the resistor and measure the value with a multi meter.
Measured value was 76.8 Ohm calculated value is 78 Ohm.
Schematic diagram:
Primary (left):
4 coils with 5 turns = 20 turns.
Secundary (right):
5 coils with 5 turns = 25 turns.
Impedance primary (50 Ohm) is 20 x 20 = 400
Impedance secundary 25 x 25 = 625
Calculated impedance secundary = (50/400) x 625 = 78 Ohm.
Comparison 5 coils with 5 turns each (above) <==> 5 coils with 6 turns each (under).
Used core: FT240-31 Amidon.
5 wires 6 turns each.
Adjustable resistor of 100 Ohm adjust for minimum SWR, disconnect the resistor and measure the value with a multi meter.
Measured value was 78 Ohm calculated value is 78 Ohm.
Schematic diagram:
Primary (left):
4 coils with 6 turns = 24 turns.
Secundary (right):
5 coils with 6 turns = 30 turns.
Impedance primary (50 Ohm) is 24 x 24 = 576
Impedance secundary 30 x 30 = 900
Calculated impedance secundary = (50/576) x 900 = 78 Ohm.
5 coils with 4 turns each.
Used core: FT240-31 Amidon.
5 wires 4 turns each.
Adjustable resistor of 100 Ohm adjust for minimum SWR, disconnect the resistor and measure the value with a multi meter.
Measured value was 78 Ohm calculated value is 78 Ohm.
Schematic diagram:
Primary (left):
4 coils with 4 turns = 16 turns.
Secundary (right):
5 coils with 4 turns = 20 turns.
Impedance primary (50 Ohm) is 16 x 16 = 256
Impedance secundary 20 x 20 = 400
Calculated impedance secundary = (50/256) x 400 = 78 Ohm.
Insertion loss measurement.
The setup:
2 x unun, first from 50 ohm to 78 ohm, second from 78 ohm to 50 ohm.
The results:
I have used the device on 80 meter. Insertion loss for two devices = 0,092 dB.
Insertion loss = 0,092 / 2 = 0,046 dB.
This means a loss of 1,05 % (see conversion tables).
In practice, when you use 100 Watts, only 1 Watt is lost in our device.
From 50 to 75 ohm withh one coil.
One coil 10 turns is output.
Input is 8 turns.
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