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Primary Radar  
User currently offlineNovice From United Kingdom, joined Aug 2012, 90 posts, RR: 0
Posted (2 years 3 months 1 week 1 day 22 hours ago) and read 3337 times:

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

8 replies: All unread, jump to last
 
User currently offlineFabo From Slovakia, joined Aug 2005, 1219 posts, RR: 1
Reply 1, posted (2 years 3 months 1 week 1 day 21 hours ago) and read 3325 times:

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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User currently offline9VSIO From United Kingdom, joined Dec 2006, 727 posts, RR: 2
Reply 2, posted (2 years 3 months 1 week 1 day 19 hours ago) and read 3294 times:
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Pulse length is also known as period, right?


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User currently offlineHaveBlue From United States of America, joined Jan 2004, 2124 posts, RR: 1
Reply 3, posted (2 years 3 months 1 week 1 day 18 hours ago) and read 3267 times:

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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User currently offlinesaafnav From South Africa, joined Mar 2010, 289 posts, RR: 1
Reply 4, posted (2 years 3 months 1 week 1 day 17 hours ago) and read 3253 times:

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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User currently offlineDavid L From United Kingdom, joined May 1999, 9546 posts, RR: 42
Reply 5, posted (2 years 3 months 1 week 1 day 13 hours ago) and read 3203 times:

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.


User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2577 posts, RR: 25
Reply 6, posted (2 years 3 months 1 week 1 day 3 hours ago) and read 3048 times:

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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User currently offlineNovice From United Kingdom, joined Aug 2012, 90 posts, RR: 0
Reply 7, posted (2 years 3 months 1 week 1 day 2 hours ago) and read 3016 times:

Thanks for that explanation David L  

User currently offlinespeedbird128 From Pitcairn Islands, joined Oct 2003, 1648 posts, RR: 2
Reply 8, posted (2 years 2 months 3 weeks 6 days 8 hours ago) and read 2580 times:

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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