[MLB-WIRELESS] Orientation of antennas

[Jason Hecker]

Ahhh,

Grasshopper, you have not maintained the correct orientation of the 
gridlines on the dish with the dipole.

I remember at Questacon in Canberra years ago they had an experiment where 
some low power microwave radiation was vertically polarised and transmitted 
to a receiver a few metres away.  You were given a flat metal grid with all 
the grid lines going in one direction, there were no cross bracing grid 
lines at all.  This was the polariser.  As you span it around, the power 
level of the microwave was altered, letting through a proportionate 
amount.  Have the grid 90 degrees to the orientation of the transmitted 
signal and none got through (the representative tone would disappear).

So yes, your ex-Galaxy antenna's grid must be aligned the same as the 
dipole, else forget it actually reflecting anything, it'll just let most of 
the signal pass right through it.



At 06:01 PM 15/07/2002 +1000, Ryan Abbenhuys wrote:
>I have an antenna orientation question too.....not quite as dumb I hope ;-p
>
>Okay, the waveguide on my AP is horizontally polarised, so of course if
>you're connecting with a galaxy or similar dish you have to swing it around
>90 degrees from the usual orientation.  However, one of my client
>connections is using one of my commercial 24's, which allows you to just
>spin the dipole 90 degrees instead of the whole dish, thus you get the full
>use of the adjustments on the dish mounts.
>.....however, after putting up with a mysterious shite signal for a few
>months I pulled it down to try something else, span the dipole back to the
>original orientation and instead spun the whole dish........and whola!!
>Connection jumps from something like -85 to -70.
>So my question is, does the reflector itself somehow have an effect on the
>polarisation??  I thought it was just the dipole itself?


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