novice
Posts: 90
Joined: Tue Aug 07, 2012 2:55 pm

Wavelength of 30-50cm
Pulse length 4 microseconds (us)
Horizontal beamwidth 1.7 degrees
Aerial rotation 5 RPM

Can anyone explain what the difference the between wavelength and pulse length of a primary radar?

Cheers

Fabo
Posts: 1154
Joined: Tue Aug 16, 2005 1:30 am

wavelength is the distance where the wave pattern is repeating (eg. pattern is up, down, down back up to zero, and then again - like a sinusoide), as in, the distance that the signal will make in about the pulselength.

Pulse length is time in which one wave pattern is emmited from the antenna, and frequency is how manny patterns are emmited in one second. 4 microseconds is therefore about 250Hz if I calculate correctly.
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9VSIO
Posts: 654
Joined: Tue Dec 19, 2006 5:00 pm

Pulse length is also known as period, right?
Me: (Lining up on final) I shall now select an aiming point. || Instructor: Well, I hope it's the runway...

HaveBlue
Posts: 2117
Joined: Fri Jan 30, 2004 3:01 pm

 Quoting 9VSIO (Reply 2):Pulse length is also known as period, right?

If that's true, then I hate being around my girlfriend when she's on her 'pulse length'...
Here Here for Severe Clear!

SAAFNAV
Posts: 394
Joined: Wed Mar 17, 2010 5:41 pm

 Quoting HaveBlue (Reply 3): If that's true, then I hate being around my girlfriend when she's on her 'pulse length'...

OWM.... Nearly chocked on my coffee! Hate those damn Pulse Lenghts...

David L
Posts: 8553
Joined: Tue May 18, 1999 2:26 am

Radar doesn't transmit continuously, otherwise it would be difficult to tell which part of the signal is being reflected. Instead, it sends a short pulse, stops to listen for a return from that pulse then repeats. The pulse is a short transmission of a signal at a certain wavelength. The pulse length is the length of time each pulse is actively transmitted.

In the example in the OP, each pulse is a signal with a wavelength of 30-50cm which is transmitted for 4 microseconds at a time.

See the diagram here: http://meteorologytraining.tpub.com/14271/css/14271_58.htm

 Quoting 9VSIO (Reply 2):Pulse length is also known as period, right?

The period is the inverse of the frequency. Since frequency is measured in Hertz, or cycles per second, the period is seconds per cycle - i.e. how long it takes the wave to go from one peak to the next.

Jetlagged
Posts: 2564
Joined: Sun Jan 23, 2005 3:00 pm

 Quoting 9VSIO (Reply 2):Pulse length is also known as period, right?

It's the wavelength which is also known as the period.
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novice
Posts: 90
Joined: Tue Aug 07, 2012 2:55 pm

Thanks for that explanation David L

speedbird128
Posts: 1562
Joined: Tue Oct 28, 2003 2:30 am

 Quoting David L (Reply 5): it sends a short pulse, stops to listen for a return from that pulse then repeats

= PRF.
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