Talk:Line-of-sight propagation

Broadcast rather than Commercial

Hello. I've edited the phrase "Commercial FM" to "Broadcast FM" - not all radio stations are commercially owned stations. Broadcast FM suits the description better. - A. N. Onymous.

Good choice. Splash - tk 16:53, 14 April 2007 (UTC)

Audio broadcasting

Why was a reference to audio broadcasting added? I think it is out of place and should probably be deleted --Fpoto (talk) 10:26, 10 November 2008 (UTC)

Attenuation through buldings/trees

100MHz signals are most definitely attenuated through buildings and trees, but the degree of attenuation of RF is dependent on frequency, as the linked graph in the article shows. Those who think the graph is not relevant in an article on "line of sight" (I don`t agree with them myself) should delete the whole paragraph, not just revert to the original, and incorrect, phrase "Broadcast FM radio, at comparatively low frequencies of around 100 MHz, easily propagates through buildings and forests".--JustinSmith (talk) 08:26, 20 January 2011 (UTC)

As long as your first sentence is concerned, one can only say that it is true, so much true to be obvious. In fact, signals of any frequency are somehow attenuated trough anything, in a way that is dependent on frequency.

But since this is true of all frequencies and all obstacles, this fact is useless, stated as such. What is useful is knowing whether a give frequency is significantly attenuated by a given obstacle for some given practical purpose.

In fact, frequencies around 100 MHz pass through buildings and trees well enough that the 88-108 MHz band is used for local FM radio broadcasting, so it is difficult to say that the original phrase is incorrect. --Pot (talk) 15:13, 21 January 2011 (UTC)

It depends what you mean by the last sentence. Anyone can try the following experiment. Get a portable FM tuner and move it round your house, the signal level will vary significantly, being its best on the side of the house towards the transmitter. This assumes you aren`t in a very strong signal area, because when it comes to RF reception signal level is everything, and most people don`t realise how much difference there can be in signal levels. --JustinSmith (talk) 09:18, 22 January 2011 (UTC)

Proposed merger of Radio Horizon with Line of Sight

I don`t agree with said merging. It`s to fundamentally misunderstand what Line of Sight actually means, which is, basically, is there anything in the way. Certainly for UHF, and even, to a certain extent, VHF, it`s not really got that much to do with curvature of the earth. This table of TV signal strengths explains it quite well, and critically, objectively.--JustinSmith (talk) 13:34, 16 February 2011 (UTC)

Just because you can see it doesn't mean its in a geometric straight line. Light (also being electromagnetic radiation propagating in a non-uniform atmosphere) bends, too. It's got everything to do with the curvature of the Earth; that's why you can't see Rome (probably) from where you're sitting, even if you have a good telescope. --Wtshymanski (talk) 14:10, 16 February 2011 (UTC)

I think reading the data on that table I linked to emphasises that, particularly for UHF, curvature of the earth is almost irrelevant, certainly compared to if there`s a hill (or trees or high buildings) in the way ! --JustinSmith (talk) 18:58, 16 February 2011 (UTC)

The linked table is virtually useless, or at least requires more scrutiny than I care to give it to tease out its meaning. Curvature limits the range. Or do British TVs work through miles of dirt? I notice the 351 metre high Belmont transmitter is given an extreme range of 55 miles (mixed units!) on its page, which correlates well to the 48 miles I get from square root of twice the height - an extra few miles can easily be due to the receiving antenna height (25 feet would do), transmitting antenna pattern, and England isn't nearly as flat as the countryside out my window right now. --Wtshymanski (talk) 19:14, 16 February 2011 (UTC)

Of course transmit antenna pattern doesn't help the range much beyond line of sight...once you can't see the antenna, you are relying on diffraction and other propation effects, which is out of the world of commercial broadcasting or taxi dispatching. --Wtshymanski (talk) 21:52, 16 February 2011 (UTC)

To be honest I don`t even know what you`re getting at by the square root of twice the height. Anyone in the RF reception business would instantly know what that table of signal levels is showing (particularly at the shop) which is that Line of Sight is [almost] everything. AS I`ve already said, when it comes to RF reception, UHF at any rate, the curvature of the earth is almost irrelevant compared to the importance of Line of Sight.--JustinSmith (talk) 22:42, 16 February 2011 (UTC)

Check out Radio horizon. This is getting tedious. You're at the line of sight distance from the tower. You keep walking with your back to the tower. What has gotten between you and the tower? If it's not trees or hills or buildings...it's the ground itself. That's what the ultimate limit on the range of terrestrial TV is - the ground gets between you and the antenna, and the only way you can get over that hill is by scattering or diffraction because you no longer have a line of sight. This exactly illustrates why the articles need to be combined, because evidently some people may think they live on a flat Earth and that everywhere has a line of sight to everywhere else. --Wtshymanski (talk) 00:39, 17 February 2011 (UTC)

You`re right, this is getting tedious, I shall make this my last conribution. To an aerial installer, certainly for TV (UHF) reception) Line of Sight means what`s in the way, as in hills/buildings/trees. The curvature of the earth is not a significant factor, the picture in this article illustrates clearly what I`m talking about. That`s Line of Sight, or not as the case may be. Curvature of the Earth may be of interest to those interested in DXing, but to anyone else, as far as UHF reception is concerned, it`s more or less irrelevant.--JustinSmith (talk) 08:21, 17 February 2011 (UTC)

If you can hit an antenna 50 miles away, why can't you hit an antenna 100 miles away? 200 miles? 1000 miles? (For that matter, why does it get dark at night?) Why do broadcasters spend so much effort making antenna towers higher? Yes, if you have a building or hill between you and the antenna, you don't have line of sight (though small objects may have enough diffraction around them to provide a useful signal). But ultimately, the Earth itself is between you and the antenna. There's a more general sense to "line of sight" than your TV installer Web site is mentioning. --Wtshymanski (talk) 14:57, 17 February 2011 (UTC)

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April 2021

Suggest merge from any unique content that might exist at Earth bulge, to avoid fragmentary and inconsistent presentation of the same facts. --Wtshymanski (talk) 20:12, 24 April 2021 (UTC)

• Oppose: The article earth bulge is about the vitual change in earth radius. To be sure it is related to the line of sight. But deals with the mathematics. The article had been created on 11 Nov.2009. Then on 5 March 2011, the user Wtshymanski copied the contents to Line-of-sight propagation. The same user now proposes merging. Since the content has already been copied to Line-of-sight propagation, it is in fact a deletion proposal, not a fair proposal. It is best to keep two articles. (By the way deleting the copied material from this article may be a good idea.) Nedim Ardoğa (talk) 09:13, 25 April 2021 (UTC)

Radio horizon comments please

Part 1 of 2

<qoute>If the Earth were a perfect sphere without an atmosphere, the radio horizon would be a circle.</quote>

Is it not a circle? viewed from above anyway, under any circumstance, assuming the antenna is balanced. Excluding atmospheric condition, which is in flux, the RH is still a circle theoretically, if not in practice, at any specific time.
or do we need to add "...without an atmosphere, mountains, buildings, competing frequency generating sources etc, the radio horizon...", maybe a bit clunky? maybe "...discounting variable atmosphere conditions, the radio horizon..."
and do we need to clarify "...would be a perfect circle."
Part 2 of 2, guys please view Very_high_frequency#Line-of-sight_calculation "...bent back toward the Earth by the atmosphere."?? CN gravity could be a candidate I feel, I want some refs and then some proof, any part help appreciated though.CheersThe Original Filfi (talk) 09:17, 9 October 2022 (UTC)

A perfect sphere implies no air or buildings. They keep them in the physics department lecture hall, right between the frictionless planes and the massless ropes and pulleys. --Wtshymanski (talk) 01:53, 25 October 2022 (UTC)

"Direct wave" listed at Redirects for discussion

The redirect Direct wave has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at Wikipedia:Redirects for discussion/Log/2023 November 11 § Direct wave until a consensus is reached. Utopes _{(talk / cont)} 07:50, 11 November 2023 (UTC)