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Old Feb 11, 2011, 05:20 PM
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Originally Posted by IBCrazy View Post
... It appears a 3 lobe wheel is more efficient and has better SWR than a 4 lobe. Circularity appears distorted.

Cloverleaf: 1.3 dbic forward, 9-20 db rejection, SWR = 1.2
Skew planar wheel: .92 dbic forward, 12db rejection, SWR = 1.3
CPOD: 1.72 dbic forwar, 19 dbic rejection, SWR = ?

First I'm glad to see the interest in doing antenna models. I would like to offer the follow suggestions:

1) Show the 3D plots. For FPV application the 2D plots are almost worthless. This is especially true when trying to compare the opposite polarity rejection.

2) Make use of variables in the 4Nec2 models so that you can more easily optimize the antenna.

3) The model will almost always show better SWR than the actual antenna where the build will have stray capacitance & inductance usually not simulated (although I have tried to incude it in some of my modeling). Getting SWR below 1.3 provides no significant improvement other than making you feel good seeing the meter reading. (The CPOD antenna model showed between 1.1 and 1.2 depending on the particular optimization)

4) Alex, I'll eventually post the CPOD model in my 3 mile omni thread along with some other models. Been a bit busy lately.

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