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

Primary Radar

Wed Sep 19, 2012 12:03 am

Primary Radar;
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
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RE: Primary Radar

Wed Sep 19, 2012 12:27 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
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RE: Primary Radar

Wed Sep 19, 2012 2:43 am

Pulse length is also known as period, right?
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HaveBlue
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Joined: Fri Jan 30, 2004 3:01 pm

RE: Primary Radar

Wed Sep 19, 2012 3:54 am

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'...  
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SAAFNAV
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RE: Primary Radar

Wed Sep 19, 2012 4:26 am

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...  
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David L
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RE: Primary Radar

Wed Sep 19, 2012 8:40 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.
 
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Jetlagged
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RE: Primary Radar

Wed Sep 19, 2012 6:34 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
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Joined: Tue Aug 07, 2012 2:55 pm

RE: Primary Radar

Wed Sep 19, 2012 8:01 pm

Thanks for that explanation David L  
 
speedbird128
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RE: Primary Radar

Sun Sep 30, 2012 1:27 pm

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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