Application Note No. 47899.15  10 GHz Slot Antennas

We recently had some slot antennas machined...32-slots for 10.368 GHz per W1GHZ.  A friend of ours had a chance to measure the antenna pattern, and as predicted by W1GHZ, there are 4-5 dB nulls in the pattern in the azimuth plane.  He added a standard white PVC-pipe radome to it, and the nulls deepened to almost infinite levels at certain angles.  Be careful with your 10 GHz radome material...try to use something very thin.  I think the bad material was about .250 in thick.  Maybe some .062 G-10 would be better.  We will post new info here, as it becomes available.

UPDATE... The azimuth pattern (E-plane) of the 32-slot waveguide antenna was found to have -17dB nulls at +/-45deg offset from the broadside direction.  W3IP reports that adding wings (around 0.75 inches) to the antenna got the nulls down to -7dB or so.  The broadside gain was found to be about the expected 12dBi value.  It appears that a uniform omni-directional pattern is in-fact-hard to achieve (as expected).   Please email your observations of slot antenna performance to me at  Tnx es 73, W3IY

P.S. Here is a very interesting link to some good slot antenna information.  It looks like they also had problems with omnidirectionality.  PE1CQQ

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