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Building a QRO 1/49 transformer for end fed antenna.

Updated: Jul 7



Used material:

- 3 cores Amidon 240-43

- copper wire 1.8 mm diameter

- PTFE tube with 2 mm internal diameter and 3 mm outside diameter

- for use > 7MHz, a compensation capacitor is required.It must withstand high

voltages depending on the power used.


SWR curve without compensation:


Smith diagram without compensation:

SWR curve with 100 pF compensation:

Smith diagram with 100 pF compensation:

SWR curve with 125 pF compensation:


Smith diagram with 125 pF compensation:

SWR curve with 160 pF compensation:


Smith diagram with 160 pF compensation:


SWR curve with 180 pF compensation:


Smith diagram with 180 pF compensation:


Insertion loss measurements from two equal devices to have a reference.


Insertion loss of our QRO device:


0.35 dB @ 1.8MHz 0.40 dB @ 3.6 MHz 0.50 dB @ 7 MHz

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