YET another antenna basics question

[roadrunnernm]

Thanks in advance for your help and patience. 

 

For the sake of this question please disregard any "isotropic antenna" information. 

 

In comparing the performance of an omni-directional antenna, I understand a vertical dipole is the standard of measurement.  "dBd" as opposed to to isotropic "dBi"

 

What would be the THEORETICAL  improvement over a PERFECT vertical dipole by

 

1)  a perfect 1/4 wave ground plane?

 

2)  a perfect 5/8 wave ground plane?

 

3)  a perfect 1/4 wave collinear (stacked) antenna? (four folded dipole antennas oriented in 90 degree offsets)

 

4)  a perfect 5/8 wave collinear (stacked) antenna? (four folded dipole antennas oriented in 90 degree offsets)

 

I am finding conflicting (surprise surprise) opinions and would like to hear from someone who has ACTUALLY seen/measured these configurations.

 

Thanks again

David

[mustangstallion]

My experience has been that a ground plane antenna has the edge over a standard ( 0-2 dbd) vertical dipole. I once had a home made 1/4 wave antenna that out performed a 5/8 wave at 20ft. The idea being that the 5/8 has a lower angle of radiation. Perhaps the signal was not projecting as well as the 1/4 wave with a higher angle to the antenna up 1500ft high. Once you start stacking dipoles, however, the added gain and pattern control makes the stacked dipole more effective than a 5/8 wave antenna because of the increased bandwidth and overall antenna pattern control. It's all about efficiency, simplicity and pattern control albeit more expensive to produce. That's why you see more high dollar commercial antennas made with dipoles. For GMRS/HAM Collinear antennas are more practical for mobile and base setups. As you have discovered antennas are never ending magic. What works for me might not work for you. Height, terrain, gain, feed lines etc all contribute to the confusion That's why antennas are made with the notion of dbd and dbi. Good luck!