Calculate magnetic loop and gamma match. - ON6YC

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Calculate magnetic loop and gamma match.


Found a download for   Magloop4   a calculator for magnetic loop antennas. After some experiments the calculator seems to be very accurate. On a 64 bit computer I' m using the Magnetic loop Calculator from KI6GD.

I found a lot of information in the paper "Underestimated magnetic loop HF antennas"  from my good  friend Leigh, VK5KLT.   Download the latest version  1.2  "Overview of the Underestimated Magnetic Loop Antennas"

Here the paper from VK5KLT about magnetic loop antennas.

Found most results of my experiments and observations confirmed by this document.

Because I want to handle the loop alone, I choose for a diameter of 2.5 meter, aluminium tube of 50 mm and the 40m band and also one for 80 m. band.

To have an idea of the radiation patern I tryed to make a simulation in  Eznec+5.
See the results below.

After several experiments I find the calculation results of Magloop4 very good. I needed less capacity. The diameter of the coupling loop is almost correct.
The coupling loop is difficult to tune for highest Q. It's also difficult to make a stable construction without any supporting material inside the loop.

So I did some research for a gamma match, couldn' t find much about it. After some experiments I came to the following dimensions:
Lenght of the gamma match tube = Circumference of the loop / 10.
For the diameter of  gamma match tube = diameter  of the loop  tube / 3.
The distance between gamma tube and loop tube = Circumference of the loop / 70. (real distance)
This dimensions works fine, even for 80 m and in almost any situation.

To tune the gamma match I made an aluminium plate with two screws to hold the distance and clamps the tubes.
Tuning is done by moving this plate in distance to the feed point. It' s very critical because of the narrow bandwidth. An antenna analyzer is a great tool for it.

On the next pages you' ll find more information about the construction.

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