[SOLVED] Helix Antenne impedance matching at 433Mhz ??

[Ivan-Holm]

Hi
We have tried to make an Helix antenna on 70 centimetres wavelength 433Mhz. we have looked at some design rules at **broken link removed** and have seen that the matching can be done by 1/4 wavelength coax cable or 1/4 wavelength stripline. but how do we calculate the distances from the ground plane and the wide, size, shape ?


Mads & Ivan

 

[FvM]

What's your motivation not to go for a simple rod (monopole) antenna? Which helix antenna mode to you want to utilize? A helical antenna in normal (or "broadside") mode is sometimes used either as shortened (< λ/4) monopole or as a monpole with increased horizontal directivity. Axial or "end-fire" mode in contrast acts as a circular polarized antenna with directivity, but needs several λ length.

 

[Ivan-Holm]

we use Axial mode. we Will like to do some antenna bearing that, why we use Helix antenna . our diameter is 21cm and our spacing is 1/4 wavelength about 17,3 cm and we don't know if the number of turns is increase the impedance and how we know the impedance of Helix Coil. we have about 8 to 10 turns over 6meter copper tube 1cm i diameter.... the guide say some thing 137 ohm impedance to there design. but not how they calculate it.

 

[FvM]

Formulas for axial mode helix antenna can be found in Balanis, Antenna Theory (3rd edition).

 

[Azulykit]

Kraus discusses the design of a helix. I have always found this to be a useful reference.

 

[Ivan-Holm]

thanks for the book title