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 Post subject: Re: What is the Maximum Range I can Get?Posted: Thu Jun 15, 2017 2:12 am
 FlightAware Member

Joined: Sun Jun 21, 2015 12:55 pm
Posts: 63
After several years of running adsb I've decided to get a FA dongle. You can see from the graphs that it did improve results. Very happy with my purchase.

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 Post subject: Re: What is the Maximum Range I can Get?Posted: Thu Jun 22, 2017 4:16 am

Joined: Fri Jun 16, 2017 7:44 pm
Posts: 24
CXA007 wrote:
With my homemade 12 segment collinear antenna, I see traffic 250+miles out regularly, for about 14,000 position reports a day at the 200mn+ range..
Having outside on my 39th floor balcony helps too

That's all about the height there, you have a direct line of sight of more than 310 miles!
http://www.calculatoredge.com/electroni ... fsight.htm

My antenna is only on top of my garage. I hate you

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 Post subject: Re: What is the Maximum Range I can Get?Posted: Thu Jun 22, 2017 11:25 am
 FlightAware Member

Joined: Sat Feb 15, 2014 3:08 am
Posts: 2036
Location: Toronto CYYZ
SoNic67 wrote:
That's all about the height there, you have a direct line of sight of more than 310 miles!
http://www.calculatoredge.com/electroni ... fsight.htm

My antenna is only on top of my garage. I hate you

That's NOT all about the height. The contribution of height of RECEIVING antenna is much less than the contribution of height of the plane.
A plane at 40000 feet, contributes 283 miles to line of sight.
A receiving antenna at 15 feet height (garage roof) contributes 5 miles
A receiving antenna at 390 feet height (39th floor) contributes 28 miles.

With antenna above garage (15 ft above ground), the line of sight = contribution of RECEIVING antenna + contribution of plane = 28 + 283 = 311 miles
With antenna at 39th floor (390 ft above ground), the line of sight = contribution of RECEIVING antenna + contribution of plane = 5 + 283 = 288 miles

Improvement going from Garage roof to 39th floor = 311 - 288 = 23 miles

.

If the antenna is surrounded by tall houses/buildings or trees, which block its view of horizon, then raising antenna above the height of these obstruction does improve message count and range. Once antenna is above these obstructions, any further increase in height brings in very little improvement.

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 Post subject: Re: What is the Maximum Range I can Get?Posted: Thu Jun 22, 2017 7:02 pm

Joined: Fri Jun 16, 2017 7:44 pm
Posts: 24
Well yes and no... To me it is important if you have buildings (houses) around you. The further the plane is, lower to the horizon it will be. That means that my line of sight cannot reach the theoretical LOS because it will have objects in the way.
If you are at the 39th floor, probably not too many tall buildings are around you. Or at least that's what I think.

An object, even if smaller height than the antennas, if is situated between them can block the LOS. Imagine one in the middle of this figure:

As my house antenna is only at 2 feet above roof, a house at 1 block away might block me - when plane is towards the extreme of my range.

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