Mounting Antenna upside down

If someone is wondering if the antenna can be mounted upside down with the tip pointing to earth: Yes, it works.

Friend of mine wanted to have the antenna mounted on his house.
After installation he identified a significant loss due to the roof where the antenna was mounted directly below.

He then made the unusual attempt to simpy rotate the antenna by 180 degrees, away from the roof.

This is the result
top the whole day yesterday, bottom the day starting from midnight, but the antenna was changed at 07:30, so this is just two hours where the number of aircraft > 320km range increased massively


Never thought it would be that easy.


The radiation pattern of a collinear antenna in the vertical plane

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The dead cone directly above will likely be worse.

But if you’re mounting it somewhat strange anyway, that’s probably not a big concern.


To me it was surprising.

My friend and I have no idea about how antennas are working in detail. It was more a “try&error”

Flightaware 1090 Mhz Antenna



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Those lobes are horizontal not vertical. If colinears had vertical radiation patterns their gain would be straight up in the air and straight down to the ground which would do nothing to increase your receive distance and messages seen except for very nearby aircraft.

Friend is using a Vinnant, not a Flightaware

This twin-coil wire collinear design is similar to Vinnant


Twin Coil - Pattern

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“in the vertical plane” in this context means that the plane of the graph is at right angles to the ground, i.e. 0 is up, 180 is down, and the 90-270 axis (where the main lobes are) is parallel to the ground.


High mounted vertically polarized antennas mounted upside down are still vertical except the antenna “ground” is now above the antenna relative to real ground. In some instances this improves reception as the lobes normally reflecting up are now reflected lower increasing range.

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If you are somehow limited than why not?! I had mine CoCo antenna hung down this way from the very beginning. Unfortunately my modeling skills are not that good to check the predicted pattern, wether if it would be much difference to mount it normally.

I know this is an old thread that has been resurrected but I looked at the above plot and it appears that, in the XY plane which I believe is the horizontal, the gain is -0.14 dB and the highest gain is 5.01dB at 60 degrees above the horizon.

I would have expected maximum gain at the horizon.

I have just retuned from holidays so maybe I haven’t kickstarted the brain yet.

BTW the Total Eclipse of the Sun at Exmouth was awesome.