I want to measure radar signals on a ship deck with a power sensor. I want to chose between directional antennas and omnidirectional antennas?
Which antenna should be better to use in this situation omnidirectional or directional?
In the attachment you can see the setup I am currently using to measure on ship decks
If you know the direction they are coming from then the antenna you have should be fine. Check its polar diagram. If you want the effect of the direct power and the power reflected from the deck then the beam has to be wide enough to see both at once, twice the elevation angle. You will get an interference pattern and you will need to move the antenna about to find its peaks and nulls. If it has a narrower beam you can point it at the source and then at the reflection and add the powers, but you won't see the peaks and nulls.
If there are complicated reflections and/or the signal is from all around, then you need an omni. Also take note of the polarizations - you need two orthogonal omnidirectional antennas with the same pattern (omnidirection antennas are not omnidirectional, they usually don't receive from directly above or directly below).
If the elevation angle for a power source is high, for instance 45 degrees, then you won't measure the right power for that source (or its reflection) with an omni because it will be about 1 or 2 dB down there. Look at the polar diagram.
What do you actually want to measure? You have a complex multi-path propagation environment with direct and reflected waves passing through your observation point. Are you interested in the direct wave from the antenna or the ensemble of waves? Define this and we may be able to help you.
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