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Re: [Paparazzi-devel] circular polarized antenna hype


From: Chris Wozny
Subject: Re: [Paparazzi-devel] circular polarized antenna hype
Date: Mon, 23 Jul 2012 13:38:17 -0400

Tilman,

After looking at David Windestål's guide on the Skew-Planar wheel and
Cloverleaf antenna, he recommends using the SPW for the receiver and
the Cloverleaf as the antenna. The reason for this being that "the
reverse polarization rejection pattern is very erratic [for the
Cloverleaf antenna] and varies between -8 and 19dBi. Therefore there
are better antennas to choose for the receiver [such as the
Skew-Planar Wheel]. This doesn’t matter for transmitting signals
though, only for receiving them." Also, he encourages the use of
circularly polarized antennas for Tx and Rx which answers your other
question.

I'm very curious about the probability of two circularly polarized
being out of phase, my initial guess would be that the chance of this
incident is very small (if possible at all.) That's just a guess
though so I'll leave the actual technical answer for one of the RF
gurus.

Also, here's a pretty awesome video about antenna polarization if
anyone wants to know more about it: http://vimeo.com/8826952

Cheers,
Chris

On Mon, Jul 23, 2012 at 9:30 AM, Tilman Baumann <address@hidden> wrote:
>
> What is up with those circular polarized antennas that are all the rage in 
> the FPW world right now?
> http://www.fpvuk.org/equipment/circular-polarized-antennas/
>
> The problems they are trying to avoid should be present in telemetry as well. 
> Which is loss of signal when antennas are out of phase. (Vertical vs. 
> Horizontal)
>
> I wonder, would it make sense to hook one of those cloverleaves to a XBee? 
> How does the fact that we use bidirectional signals the efficiency of those?
> Has anyone tried? Should trials be made?
> Do I understand correctly that only one side should be circular polarized? Or 
> should have receiver and transmitter the same antenna?
>
> I thought I bring that up since it has not been discussed here as far as I 
> know. I'm curious in your opinions.
>
>  Tilman



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