Radar

Two sorts, primary and secondary.

Both are high frequency radio waves say 1,000 mhz range for some secondary.

Primary bounces a rotating beam off distant objects (say planes) from the time and direction of this 'echo' the range and direction can be calculated/displayed.

(hence the acronym RAdio Direction And Ranging)

Secondary radar transmits a pulsed code, the airoplane receives this and transmits a coded reply on a slightly different frequency giving the plane's identification and other information e.g. friend or foe.

Thank u sir

Mr. Cat, with all due respect, you shouldn't answer forum questions about which you clearly have no clue.

There are *several* types of radar (Doppler - for speed determination, monostatic - the norm for air traffic control & weather, synthetic aperture, etc.) and they operate at frequencies from hundreds of MHz to millimeter wave (depending on application, target type & environment).

There is no such thing as 'primary and secondary', those terms carry no meaning in describing radar that I know of - where did you see or hear that?

Your description of what you term 'secondary radar':

"Secondary radar transmits a pulsed code, the airoplane receives this and transmits a coded reply on a slightly different frequency giving the plane's identification and other information e.g. friend or foe."

has NOTHING to do with and is NOT 'radar'; as contained in your own description, such systems are called IFF (Identify Friend or Foe, owing to their original military application) systems. The device returning the IFF information is called a 'transponder'; it's signal is emitted (and subsequently received) LONG after the triggering pulse has passed behind the aircraft, long after a RADAR pulse would've bounced back and been received.

One of the Old Masters in radar is Merril I. Skolnik whose 'Radar Handbook' remains a classic. If you do a search at Amazon on 'Skolnik radar' you'll turn up his books (Intro & Handbook) along with some other good introductory texts. Another excellent source on-line is microwaves 101:

http://www.microwaves101.com/encyclopedia/radar.cfm

Regards RF_guy

Mr. Cat, with all due respect, you shouldn't answer forum questions about which you clearly have no clue. LOL...

I worked for Cossr (Raytheon) in Harlow England for many years...

The Secondary Serveillance Radar at Londons Stansted and Gatwick Airports was built/installed by Cossor/Raythoen and tested by me where I was senior QA Development Engineer.

I suggest you google Secondary Surveillance Radar.... or IFF... wiki has a good entry.

I never knowingly talk Bull..... I always reserve the right to be wrong....

But on this one? Nah...

Hopefull the due respect you so kindly mention will be forthcoming shortly.

A somewhat aghast

Del the Cat

Try this

'There is no such thing as 'primary and secondary', those terms carry no meaning in describing radar that I know of - where did you see or hear that?'

Try this ... ICAO (1978) civil aviation journal which shows Cossor Primary linked with Raytheon Secondary... (in No1)

My knowledge here is limited, so I shall simply read with interest. Raytheon as in ADS ? Are you in on that thread Del, I can't remember ? Hmmm, bet you is !

Hey..that's proper Sci-Fi

Oh yes... we did the heat ray thing.

Raytheon is still a big employer in Harlow, just about everyone has worked there at some time. We have GSK now too...

Oh, just remembered I tested the Air Traffic Control systems at Newcastle and East Midlands too ......

That'd be a good project for the Work Shop Blog.?.. Turn your microwave cooker into a Primary Radar.

I believe one of the first microwaves was called the Radar Range....

But hey ...what would I know?

But hey ...what would I know?

Yeah, you shadup yer mush Del. Stick wiv solee panels and stuff. In fact, no - You play safe and keep it limited to opening the curtains once a day. For some reason I dont't have curtains. Or windows and stuff. And I've got good wall insulation. Toasty. Now I know why all those fit birds up in Newcastle wear micro-skirts in mid Winter. I suppose the blokes in T-shirts were ADS 'collateral', but worth the price I'd say.

LMAO

And another thing!

The device returning the IFF information is called a 'transponder'; it's signal is emitted (and subsequently received) LONG after the triggering pulse has passed behind the aircraft, long after a RADAR pulse would've bounced back and been received.

Oh dear, WRONG AGAIN...

The response is timed from the received pulse train, it wouldn't be much good if it wasn't! If an enemy plane is bearing down on your Rapier battery you can hardly wait!

My original response to the thread was a thumbnail sketch aimed as someone who presumably knew nothing about radar.

I could go into endless boring detail, but brevity is a virtue, and having signed the official secrets act, I feel it would be foolish to start quoting frequecies and pulse spacings.

I feel that maybe by now I have demonstrated that I'm not the one who 'doesn't have a clue'

I suggest you aim with more care before shooting next time.

Del

"How does RADAR work?"

Short Course In Radar Fundamentals

There are various types of RADAR. Radar is RAdio Detection And Ranging.

One type generates a pulse that is sent out from the transmitter (generally some sort of parabolic dish or phased array antanae). These pulses strike the object and generate a return pulse which is detected by the receiver. The RAnge is then extrapolated from the time required for round trip of the pulse.

Another type or RADAR (doppler), generates a pulse which strikes the object and generates a return pulse but this time, in addition to calculating the range to the object, the receiver also checks the frequency of the return pule to determine if the frequency is slightly faster or slightly slower than the pulse originally transmitted. This will tell the operator if the object is moving toward or away from the antanae and the speed of the object. Multiple RADAR antanaes are sometimes used together to paint a three demensional representation of the object. In this manner, the course, speed, direction, location, and elevation of the object can be determined.

Secondary Surveillance Radar

Secondary Surveillance Radar is referred to as "secondary", to distinguish it from the "primary radar" that works by passively bouncing a radio signal off the skin of the aircraft. Primary radar works best with large all-metal aircraft, but not so well on small, composite aircraft. Its range is also limited by terrain and rain or snow and also detects unwanted objects such as automobiles, hills and trees. Furthermore not all primary radars can estimate the altitude of an aircraft. Secondary radar overcomes these limitations but it depends on a transponder in the aircraft to respond to interrogations from the ground station to make the plane more visible and to report the aircraft's altitude.

How did we get off on tangents such as IFF and ADS? The originator only asked "How Does Radar Work?"

There are conceivably a grunch of tangents available to boggle the original inquiry.

"How did we get off on tangents such as IFF and ADS? The originator only asked "How Does Radar Work?""

Because? Just Because? Or some posters DO NOT READ, 1. The OP, 2. ALL of the replies, or feel compelled to have their say whether OT or OFF and just opinionate & bloviate!