[MLB-WIRELESS] Orientation of antennas

[Ryan Abbenhuys]

Ahhhh, thankyou very much donkeydick.

The antenna i'm using is one of these
http://www.alphalink.com.au/~sneeze/pics/antenna.jpg
So taking in what you have said I can see exactly why the signal was so bad!

I was pretty sure it would be obvious to one of you antenna geeks on here
;-)

----- Original Message -----
From: "Jason Hecker" <jason at air.net.au>
To: "Ryan Abbenhuys" <sneeze at alphalink.com.au>;
<melbwireless at wireless.org.au>
Sent: Monday, July 15, 2002 6:20 PM
Subject: Re: [MLB-WIRELESS] Orientation of antennas


> 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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