[MLB-WIRELESS] Orientation of antennas

[Tony Langdon]

> Here is a really, really dumb question.
> 
> I've just installed two helical antennas made to Jason 
> Hecker's design.
> 
> I've installed them "upright" becuase this is the logical 
> thing to do and
> nothing in Jason's instructions says to do any different.

As in if it was a screw, the end of the screw would be pointing to the sky?

> 
> Been looking at a few other sites today, one of them is 
> openly (with full
> atribution and gratitiude) a version of Jason's design. The 
> photos of the
> completed antenna shows it installed horizontal.
> 
> Am I missing something?

This type of helical is an "axial mode helix", which means it fires the RF
out the end of the helix, so you have to have it so it's pointing towards
where you want to put the link to.  These antennas are quite unlike the CB
helicals or handheld "rubber ducks" (which are "normal mode helicals", BTW)
that radiate most to the sides of the antenna.

Whether a helical antenna is axial or normal mode is determined by the
diameter and spacing of the turns (normal mode helicals have turns that are
a small fraction of a wavelength in diameter, and often closely spaced).

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