Talk:Radar cross section

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[edit] Removal of statement about downtime

This conversation was moved from my talk page to here. =Axlq

Hi. You removed my sentence regarding outdoor and indoor test ranges from the article "Radar Cross Section" saying it was unsourced and untrue statement. But I read it in the very first reference - Knott and Shaeffer that outdoor test ranges typically suffer a 35% downtime. Also indoor test ranges suffer the limitation of the size of test object. Is it wrong? Saurabh Sardeshpande 13:27, 21 March 2007 (UTC)

I removed the sentence for two reasons: I couldn't find the citation associated with it (you did), and it contained a false statement that they cannot be used in "unfavorable" weather (regardless of what the reference says, I know from professional experience that such a statement is false). Removal of the part about 35% downtime was unintentional. I believe I have the Knott/Shaeffer reference at work - would you mind telling me where you found the statement? I have no problem with restoring the sentence. =Axlq 02:50, 25 March 2007 (UTC)
The part regarding downtime is in the very first chapter of Knott and Shaeffer on page 13, paragraph 3. I also read this part in lecture notes of Robert W. Borek which I stumbled upon while browsing. I reproduce the part below:
  • Indoor ranges suffer limitations in the size of the targets that can be measured, whereas outdoor ranges suffer down time problems due to weather conditions. Although the indoor ranges offer protection against the weather and intruders, outdoor ranges can often measure full-scale targets under far-field conditions.
  • Probably the single most important disadvantage of outdoor measurements is the long-term effects of weather. Measurements cannot be made in the rain because of moisture collection on targets and target support columns and the backscatter from raindrops in the measurement zone. When rain is not a problem the wind usually is.
You have Knott/Shaeffer at work and you have professional experience in test ranges? What do you do? I am doing my undergraduate seminar on 'Radar Cross Section' and hence am interested in the topic. Saurabh Sardeshpande 07:35, 26 March 2007 (UTC)
Ah. What you quoted above is quite different from saying that outdoor ranges "cannot be used in unfavorable weather." Yes, they suffer downtime due to weather because most measurements require good conditions, but they are used in unfavorable weather, if the purpose of the measurement is to include the effects of weather. Again, I have no problem restoring your edit. My objection really focused on the phrase "cannot be used".
Yes, I have professional experience in test ranges. I don't have the same job anymore, but in the past I planned and participated in radar test events for Navy ships. Those outdoor ranges usually consist of a radar mounted on shore, tracking the ship a few miles away while turns in slow circles. Because there are no support columns fixing the target in place, you must contend with variable distance to target. Having different weather conditions was valuable for characterizing the distribution of RCS as a function of weather or sea state. Another version of a Navy outdoor range involves a helicopter flying around the target, with the measurement radar in the helicopter. Either version requires a precise transponder to be mounted on the target so that you can perform downrange distance corrections in post-processing later. =Axlq 15:05, 30 March 2007 (UTC)

[edit] Spurious definition of RCS

This statement (in the first paragraph) is spurious:

"The RCS of a target object is equal to the cross-sectional area of a perfectly conducting sphere that would produce the same magnitude of reflection as that observed from the target object."

It is only correct (or, at least, approximately so) in the high-ka limit. A clear way to demonstrate its invalidity is to ask "What is the RCS of a perfectly conducting sphere?" By the definition given above, it must be, at all frequencies/wavelengths, \pi a^2, the cross-sectional area of the sphere. But, of course, in the resonance region the RCS of a sphere is not constant; it wobbles about the high-ka limit. And in the low-ka limit the RCS falls precipitously.

The correct definition for RCS is stated later in the article: \sigma = 4\pi P_backscatter / P_intercepted

You are correct. I made some changes to the article to clarify that the RCS is the same as a sphere only when the target spans several wavelengths. =Axlq 18:50, 5 July 2007 (UTC)

[edit] Article is too hard to understand

Wikipedia isn't just for specialists in... god knows what it's called "Radarography" lol, it's for uneducated people to educate themselves too. Now I've been reading up on radars at HowStuffWorks.com and I still don't understand this article. I know essentially that a large RCS means a big blip on the radar screen at home receiving its "rays" or whatever, that bounced off a plane it zapped for example. But I didn't learn that from here, take for instance the opening line. It says;

Radar cross section (RCS) describes the extent to which an object reflects an incident electromagnetic wave. It is a measure of the strength of the radar signal backscattered from a "target" object for a given incident wave power.

WTF is a "incident electromagnetic wave"?, I know "electromagnetic" is linked but it doesn't explain this incident wave thing. What's backscattering? Then it hits you with a "given incident wave power"!

Now I know the opening line has been the subject of some debate recently, but it's not just the opening line. Perhaps we could save the formula in the definitions section for the calculation section, and an example of RCS would be very very helpful. I think we should try and explain the basic concept in very basic terms to dummies like me, in the opening paragraph. Then the rest of the article can be used for all the factual encyclopaedic knowledge. Please don't think stupid of me, I just don't know about radars. I'd love it if someone could send me a condescending dummed down explanation of RCS please, then perhaps we could work together to make the article a bit more easy to understand.Ryan4314 (talk) 21:24, 1 January 2008 (UTC)