Can raising antenna help improve reception ?
My antenna is at 53 feet and can raise it between 6 and 9 feet.
Please advice
If you have no local obstructions, you may be into the relm of diminishing returns, but in general terms, height is king when it comes to antenna location.
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Height is might! Even if you are already above nearby obstructions, the increased antenna height raises your antenna’s line of sight to a new, more distant end point on the curvature of the earth.
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It’s worth increasing the height of your antenna to clear local obstructions. Once it has a clear view, there is not a great deal to be gained by raising it further, unless you can do so very significantly. A few feet is not going to make a lot of difference because the majority of range is determined by the altitude of the aircraft.
If you can do it easily then it’s worth it. If you have to spend a lot of money to get the height by installing a more substantial mast then it’s probably not.
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Do you see out to 200 NM and beyond now in all directions?
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If you do not have close obstacles (e.g trees or other buildings), the effect would be almost zero by changing only 6 to 9 feet.
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@caius
@geckoVN
@foxhunter
You are 100% right.
Click on the Diagram to See Larger Size
Click on the Diagram to See Larger Size
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Well,the numbers tell the true story. I’m going to my room now!
Given your location, you have a significant chance of enhanced propogation over water. So giving the antenna a good view of the water may receive some distant signals.
Looks like you’d have a good spot for AIS if you have any interest in ships.
Not 100%.
That diagram makes the point, but is high shool level geometry and doesn’t take into account effects like the Fresnel Zone.
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I do have interest in ships and I also have an AIS station closer to the shore.
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Maximum Range at Curacao (Lat 12.1, Lon -68.9, antenna height above ground 53 feet) as per heywhatsthat.com
- Yellow curve is for planes at 10,000 feet
- Blue curve is for planes at 40,000 feet
Great. 
What hardware & software do you use for your AIS Station?
I use a raspberry pi from vesseltracker.com
It came with their software on it, and works great.
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I used to feed AIS for MarineTraffic (Kpler Company). They supplied a (sealed box) receiver that seemed to be an RPi with custom software, 3 meters of coax and a large VHF marine antenna that I placed in my attic. Reception limit was about 30 miles.
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The question was about a few feet. And this makes the difference of only 1-2 miles. It’s pretty unlikely that you will see aircraft just passing your receiver in this distance.
The majority of aircraft you will see either for that mile earlier or longer (depending on the flight direction).
So the change total number of aircraft will increase by less than 1% 
Changing the receiver hardware (e.g. from Flightfeeder to Airspy) can have a more significant change in reception range. At least this is what i got during my different setups over the last years.