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  • Writer's picturextgaby

Building an endfed antenne kit (from with 1:49 transformer.

Updated: Mar 19, 2021


Buiding the transformer:

1) drilling the holes 2) Placing the hardware

3) Schematic 4) Winding the transformer

Primary (green wire) 2 turns + 100 pF parallel. Secundary (brown wire) 14 turns.

5) Installing the transformer 6) Testing

For testing the unit, a resistor of 2.500 Ohms was placed between the output and the mass.

winding the coil:

I took 10 cm to make the coil. Wire diameter = 0.5 mm. This results in approximately 200 turns.

Measured value = 120uH

Connecting the coil to the antenna wire. finish with heat shrink.

Measuring results:

80 Meters 40 Meters

20 Meters 15 Meters

10 Meters Minimum values

SWR curve 80 meters shows a very narrow bandwidth. This is due to the high coil value and the very short extension on 80 meters. My coil is 120 uH instead of 110 uH and my 80 meter extension is only 1.5 meters instead of 2.5 meters.

Some tests are planned in the future with a smaller coil value and a longer extension.

SWR curve 40, 20 15 and 10 meters the results show a too low resonance as the wire is just a little bit too long. Will be adjusted in combination with the planned works mentioned above.

SWR curve 20 meters

SWR curve 15 meters

SWR curve 10 meters

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