www.webx.dk Start page

MY little Radio Control page

Also see the video wireless page if you like.

Foreword:
All antenna measurements are made indoor and moved to minimum reflections and as flat response as possible,
distance from antenna to antenna exactly one meter, cables and plugs calibrated to zero dB,
all curves are from 2.3 to 2.5GHz so the band we use are in the mittle.

Curve 1: Whip to Whip - pointing same way -35dB
Actually I think that -36dB is more right avarage

Curve 2 : 1/4 GP to 1/4 GP - pointing same way and in same height -36dB

Curve 3: Whip and my improved Patch - The whip and patch was rotated to best signal about -32dB
Actually I think that -31dB is more right avarage
Compared to the Whip - Whip result -36, this one is 5dB better that is 8dBi gain
But remember most important of all factors, this one is circular polarized !! so there is no holes to be seen when rotated !!
this is what we like when using it to receive RC video from a plane in any angle.
patch5.pdf HERE is the drawing of my modified and improved mr-cam patch.

Curve 4: whip to whip , pointing 90 degree angle, I think that -53dB is more right avarage, so its important to point two whips same way !
so the change is from -53 to -36 = 17dB the reson for only measuring a 17dB drop is maybe reflections, and dynamic range of analyzer.
the teoretical 90 degree angle attenuation should have been 24dB.

Curve 5: Whip to Zyxel Patch - this type of patch is not circular, so it MUST be rotated right like here : -32dB

Curve 6: Zyxel to Zyxel patch - again angle is important, best result -25dB
The Zyxel antenna we tested is called : EXT-109 Outdoor 9 dBi Directional Patch Antenna.
if you compare the -25dB result with the whips -36dB the difference is 36-25 = 11dB better for two antennas,
so one patch has 11/2 = 5.5dB gain, that is 8.5dBi so that is very close to the 9dBi they call their antenna :-)
but this type of Patch antennas that is NOT circular polarized, so it will make a bad receive antenna for RC video, since planes can be in any angle.

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Thomas Scherrer OZ2CPU March 2007