I have made a vertical antenna with a lengt of 10 meters and two radials of 10 meters also connected to the ground. This antenna resonates at 7.200 MHZ. I want to use this antenna at 3.700 MHZ.
The value measured with the NANO VNA was 97 ohm -j367 ohm.
Antenna is too short at this frequency so it behaves capacitive (-J).
I have used the software:
https://www.fritz.dellsperger.net/
This is a very good program to see and understand how antenna matching can be done.
Here you can see the result of the measured value displayed on the smith diagram.
We are moving from DP1 > TP2 by te use of 14 meter of coax with a Vf of 0.86
After placing the 14 meter coax, you have to place a stub short cirquited at the end, with a lengt of 2.1 meter with a Vf of 0.86.
Then you will end in the center of the smith diagram:
Picture of the stub in the garden.
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