Timeline for How to compute each of these link budget terms?
Current License: CC BY-SA 4.0
9 events
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| Sep 10 at 19:59 | history | edited | Ryan C | CC BY-SA 4.0 |
added more links, cleaned up formatting
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| Nov 23, 2021 at 20:53 | history | edited | Ryan C | CC BY-SA 4.0 |
Added new paragraph at start to discuss the dangers of taking different link budget component terms from different authors having incompatible definitions.
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| Nov 18, 2021 at 18:51 | comment | added | Ng Ph | We don't consider human errors, roundings, using wrong units, etc... in link-budgets. But we do take into account seriously the statistical nature of the prediction, especially when weather is a significant factor. Link-budgets for TV broadcasting for ex., have the concept of worst-month. There are ITU models to compute the rain attenuation not exceeded for X% of the worst-month, for a given frequency and a given category of climate (temperate, tropical, ...). | |
| Nov 18, 2021 at 15:39 | comment | added | Ryan C | @NgPh In that case, all is well. :) My biggest hurdles in explaining link budgets are always the statistical nature of signal detection (even at higher SNR than "closes" your link, there is still nonzero BER) and the controversy over whether human error --- the probability that a programmer made a mistake in the software, or that someone installed the hardware wrong, or that the operator pressed the wrong button --- counted as something that could be changed, or just endured (like weather), and where (if anywhere) we were allowed to carry a margin for that. | |
| Nov 18, 2021 at 10:13 | comment | added | Ng Ph | Don't get me wrong. It was not a criticism. I am a retired engineer and sometime am amused at how scientists struggle with engineers' practice. You did a good job explaining this. Barnwell's paper is clearly written for engineers. The reproaches I have on this paper are: (i) the confusing terminology (efficiency, gain,loss, attenuation, ...) and (ii) somewhat a lack of modesty (honesty ?). When you can't justify precisely, it's ok to say "this is my margin". BTW, Barnwell has a 3 dB "implementation margin" too, on top of the numbers given in Annex. | |
| Nov 17, 2021 at 22:20 | comment | added | Ryan C | @NgPh by academic training, I am a theoretical particle physicist. As such, I know all too well that what scientists do all day is solve equations we know are wrong but are useful anyway because they model real behavior well enough to enhance understanding. I have worked with experts in atmospheric chemistry and radiative transfer physics and meteorology and all the many other disciplines necessary to build and operate functional weather satellites, and appreciate how hard they all worked. There simply is not enough time to know it all, much less explain more than a tiny fraction. | |
| Nov 17, 2021 at 18:47 | comment | added | Ng Ph | This is the type of answer that illustrates the difference between an engineer and a scientist. An engineer plays with numbers until "it works" then "moves on to other problems". A scientist wants to explain why it works. | |
| Nov 16, 2021 at 2:20 | history | edited | Ryan C | CC BY-SA 4.0 |
greatly expanded section on pointing loss
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| Nov 15, 2021 at 18:31 | history | answered | Ryan C | CC BY-SA 4.0 |