best antenna

[fungus]

AFFECT OF HEIGHT OF ADS-B RECEIVING ANTENNA ON THE RANGE:

Height of ADS-B Receiving Antenna does NOT appreciably affect the Range.

In case of Ground-to-Ground Communications at UHF/Microwave, the heights of both the receiving and transmitting antennas greatly affect the range.

In case of Air-to-Ground ADS-B Communications, the Transmitting antenna is on the Aeroplane, which is several thousand feet high. The contribution of height of receiving antenna to the overall range is therefore not appreciable.

The range is combination of ranges of transmitting & Receiving antennas. Overall Range = Range of Transmitting Antenna + Range of Receiving Antenna = 1.41 x √h1 + 1.41 x √h2 miles, where h1 = height of transmitting antenna in feet. h2 = height of receiving antenna in feet.

Based on these formula, I have calculated the Range for various heights of Receiving Antenna and Airplane, and have tabulated the results. These results show that increasing height of RECEIVING Antenna from 25 to 200 feet does not appreciably affect the overall range of ADS-B.

PLEASE SEE ATTACHED PICTURE BELOW for the tabulated results:

[ATTACH]3172[/ATTACH]

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Thanks for that. I have seen that previously and I find it interesting however, I'll stand by my own experience here and as I said I've not only increased coverage but also range simply by increasing the height of the antenna. Further improvements were found by improving the cable (reducing the losses). I can also pick up aircraft down to a lower altitude with a higher antenna although that's more to do with overcoming obstructions as I have a lot of infrastructure between myself and the airport. If height had no relevence then Air Services Australia could mount all their receiving antennas on a biscuit tin rather than on a tower. You only have to look at what you've said about the curvature of the earth and you can see that the higher the antenna, the further will be your range (or 'potential' range, depending on those ever present obstructions).

Regards,
Gregg

[VE6CPP]

I cannot honestly agree with that either ! In the VLF, HF, VHF frequencies..there is 'other types of propagation'..ie: E Layer, F Layer, Aurora, etc. At 1090Mhz..(other than Rain Scatter, maybe some types of F2 layer prop ?) it is normally 'LOS' ! (Line of Sight) at these frequencies..so an antenna 200 feet high..should show a definate improvement over one at 25 feet high ! I am conducting some tests here on 'Feedline, Antennas, etc..) So will post my observations soon. But 'interesting topic' for 'All to Enjoy' !
Jerry
F-CYQL1

I cant say I agree there on the point you make about increasing the antenna height not increasing range or coverage. I've proved it myself with my setup. I think you are getting mixed up between range and gain. It wont help gain but sure helps range to increase the antenna height, although due to the curvature of the earth and physical limitations in height etc you will inevitably hit a 'ceiling' which you've rightly pointed out in a later post. I've more than doubled my coverage (the total number of aircraft I can 'see' at any given time) and increased the range of my receiver by a good 50nm by simply increasing the height of the antenna and improving the cable. Obviously what you say about obstructions is correct, that's a different issue. If some one is already cleared of obstructions, adding height wont affect that.

Regards,
Gregg

[fungus]

Jerry,
Thanks and it is a very interesting topic indeed, even for a relative novice like myself, although in saying that I did spend much of my working life in the electrical industry so have some knowledge of the subject.

Regards,
Gregg

[abcd567]

Please see attched 2 sketches which give a visual picture of height-range issue:

uploadfromtaptalk1389142488834.jpg
uploadfromtaptalk1389142537924.jpg

[fungus]

Please see attched 2 sketches which give a visual picture of height-range issue:

[ATTACH]3173[/ATTACH]
[ATTACH]3174[/ATTACH]

That first pic proves the point. Reduce the antenna height to 30 feet and see if you've got the same range. It's even in the equation, and I'm not that great at maths. If the square root of the antenna height is less (due to reduced height of antenna) then the range will be reduced. The same applies for the height of the aircraft.

Regards,
Gregg

[abcd567]

That first pic proves the point. Reduce the antenna height to 30 feet and see if you've got the same range. It's even in the equation, and I'm not that great at maths. If the square root of the antenna height is less (due to reduced height of antenna) then the range will be reduced. The same applies for the height of the aircraft.

Regards,
Gregg

The antenna component of range with 60 feet height is 10.9 miles. Reducing antenna height to 30 feet i.e 1/2 of 60 feet, will reduce antenna component by squre root of 1/2 which is 0.7. The antenna component will be now 10.9 x 0.7 = 7.36 miles ...so far so good...Now let's see total range i.e antenna component+aircraft component.

With 60 feet high antenna, range = 10.9+109 = 119.9 miles

With 30 feet high antenna, range = 7.36+109 = 116.36 miles

So reducing antenna height to 50% results in reduction of range to 100x(116.36/119.9)= 97% i.e a reduction of 100%-97%=3%

Yes there is a reduction in range, but in what proportion? 50% in height vs 3% in range.

And this is for an airplane flying at an altitude of only 6,000 feet. Calculate for an aircraft flying at an altitude of 36,000 feet, and result will be about 1.2% reduction in range for 50% reduction in antenna height.

[fungus]

The antenna component of range with 60 feet height is 10.9 miles. Reducing antenna height to 30 feet i.e 1/2 of 60 feet, will reduce antenna component by squre root of 1/2 which is 0.7. The antenna component will be now 10.9 x 0.7 = 7.36 miles ...so far so good...Now let's see total range i.e antenna component+aircraft component.

With 60 feet high antenna, range = 10.9+109 = 119.9 miles

With 30 feet high antenna, range = 7.36+109 = 116.36 miles

So reducing antenna height to 50% results in reduction of range to 100x(116.36/119.9)= 97% i.e a reduction of 100%-97%=3%

Yes there is a reduction in range, but in what proportion? 50% in height vs 3% in range.

And this is for an airplane flying at an altitude of only 6,000 feet. Calculate for an aircraft flying at an altitude of 36,000 feet, and result will be about 1.2% reduction in range for 50% reduction in antenna height.

So there is an increase in range for an increase in antenna height. It's now down to a question of how much.

I'm presently in the process of having my antenna increased from 20ft to 30ft. That's a near enough to a 50% increase if my maths is correct. I'll let you see the results next week after the job is completed and I get some plots. The last time I increased the height of the antenna my laptop could barely handle the strain of all the extra aircraft and I got a 50nm increase in range on average depending on direction. I'll let the experience be the judge over the theory.

Regards,
Gregg

[abcd567]

.......The last time I increased the height of the antenna my laptop could barely handle the strain of all the extra aircraft and I got a 50nm increase in range on average depending on direction. I'll let the experience be the judge over the theory.

Regards,
Gregg

The eatrh's surface is not a perfect sphere or plane, but has undulations. Your last time experience indicates that the above-sea-level elevation of your location is less than the above-sea-level elevation of the area surrounding you, casting a shadow. Your increase in antenna height has acually overcome the shadow effect of your surrounding terrain, like raising your indoor antenna to roof top overcomes the shadow of your neighbour's house.

[peterhr]

I suspect there is a secondary factor coming in to do with interference of signal with reflected signal, increased height reduces the effect.

(Lloyd's mirror but in reverse)?

[VE6CPP]

Good article on tropo scatter propagation: http://www.qsl.net/oz1rh/troposcatte...oscatter99.htm
Written more for the Ham Radio Operators..but does cover ADS-B frequencies as well ! Quite lengthy..but interesting article. Share via the Pacific Northwest VHF Society.

[glen4cindy]

Should there be a gap or no gap when building a collinear antenna?

The guy in this YouTube video is not putting a gap between each segment:

http://youtu.be/TkUYdCPFXXs

While the guy in this article suggests building virtually the same antenna, but, suggests a tiny gap between each segment with a dab of silicone between each gap.

http://www.arrl.org/files/file/QST/T...Jan2013QST.pdf

How would gap vs. no gap affect the operation of the antenna?

[peterhr]

You need to ensure you don't create a short circuit between the braid in adjacent sections - tape or silicon does the same thing, silicon is more messy though.

Sent from my Nexus 4 using Tapatalk

[Rooster]

leaving a gap would incur a phase difference, as the gap would effectively become "feeder".... but:

I honestly think far too many people are MASSIVELY over thinking this stuff... What is the advantage of covering half the planet? surely the idea is to get many stations covering the globe in" cells"?
what does one person gain by having massive coverage?

Sent using Tapatalk from my ZX81

[abcd567]

.........I honestly think far too many people are MASSIVELY over thinking this stuff... What is the advantage of covering half the planet? ............
.......what does one person gain by having massive coverage?

Sent using Tapatalk from my ZX81

Maybe the same pleasure Archimedes or Newton felt when they discovered riddle of water spilling out of bath tub/apple falling on head.....or may be same pleasure as Alexander the Great felt in conquering half the known globe....



Sent from my N762 using Tapatalk 2

[glen4cindy]

leaving a gap would incur a phase difference, as the gap would effectively become "feeder".... but:

I honestly think far too many people are MASSIVELY over thinking this stuff... What is the advantage of covering half the planet? surely the idea is to get many stations covering the globe in" cells"?
what does one person gain by having massive coverage?

Sent using Tapatalk from my ZX81

I just want to see "something".

All I have now is the antenna that came with the dongle, and I have it perched on my roof with an extension cable going down to my Pi which is currently as close as I can get it without drilling a new hole in my house.

So, I've built this collinear with 16 sections. I can't really put it super high, I'm going to try to get away with it, but, I'm not sure how far I'll get due to HOA rules.

I'd like to put it next to my DirecTv dish, and put a label on it saying "Digital Television" or something, so I can "say" it's a DTV antenna. Nobody but me would know the difference.