Antenna Construction Accuracy|
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Posted by Jeff Liebermann on December 17, 2004, 3:09 am
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probably from this newsgroup. One of the most common questions is "how accurate do I have to cut the parts?" Let's grind the numbers. The wavelength of 2.4GHz is: 3*10^8 meters/sec / 2.4*10^9 Hz = 0.125 meters At this frequency, the length distance per MHz is: 0.125 meters / 2.4*10^9 Hz = 52*10^-6 meters/MHz Assuming we aim for center frequency, the 2.4GHz band is about +/-40MHz wide: +/-40 * 52*10^-6 = +/-2.1 mm Therefore, if you want to stay within the band limits, the cut accuracy has to be well below plus or minus 2.1 mm of design dimension. My guess is within 0.5mm will work well. Lose the rulers and tape measures and get out the calipers. -- Jeff Liebermann jeffl@comix.santa-cruz.ca.us 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 AE6KS 831-336-2558 | |||||||||||||||||||||||||
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Posted by Mark McIntyre on December 18, 2004, 2:02 am
Please log in for more thread options In astronomy, quarter-wave accuracy for optical surfaces is considered very good. For radio astronomy, the same is required. WiFi is merely radio astronomy on a smaller scale. So I'd suggest you'd find anything better then +/- 3cm would work just fine..... >dimension. My guess is within 0.5mm will work well.
This would certainly be very nice tho... :-) -- Mark McIntyre CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt> | |||||||||||||||||||||||||
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Posted by Dave VanHorn on December 17, 2004, 9:52 pm
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> In astronomy, quarter-wave accuracy for optical surfaces is considered
> very > good. For radio astronomy, the same is required. WiFi is merely radio > astronomy on a smaller scale. So I'd suggest you'd find anything better > then +/- 3cm would work just fine..... You'll be really sad then.. 1/4 wave accuracy in constructing a dish that's also built to that scale.. Let's see a 6" mirror is how many wavelengths across?? For most antenna work, regardless of frequency, you want to stay around 1% accuracy on dimensions. Gets tough up here, as the difference between a square cut and a rounded end on a wire is significant. | |||||||||||||||||||||||||
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Posted by on December 17, 2004, 10:22 pm
Please log in for more thread options >In astronomy, quarter-wave accuracy for optical surfaces is considered very
>good. For radio astronomy, the same is required. WiFi is merely radio >astronomy on a smaller scale. So I'd suggest you'd find anything better >then +/- 3cm would work just fine..... In radio, 1/4-wave _is_ the antenna length, not the tolerance... | |||||||||||||||||||||||||
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Posted by Mark McIntyre on December 18, 2004, 2:22 am
Please log in for more thread options On Fri, 17 Dec 2004 00:09:36 -0800, in alt.internet.wireless , Jeff
>I keep getting email asking for help with antenna construction,
>probably from this newsgroup. One of the most common questions is >"how accurate do I have to cut the parts?" Let's grind the numbers. > >The wavelength of 2.4GHz is: > 3*10^8 meters/sec / 2.4*10^9 Hz = 0.125 meters In astronomy, quarter-wave accuracy for optical surfaces is considered very good. For radio astronomy, the same is required. WiFi is merely radio astronomy on a smaller scale. So I'd suggest you'd find anything better then +/- 3cm would work just fine..... >dimension. My guess is within 0.5mm will work well.
This would certainly be very nice tho... :-) -- Mark McIntyre CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt> | |||||||||||||||||||||||||
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>probably from this newsgroup. One of the most common questions is
>"how accurate do I have to cut the parts?" Let's grind the numbers.
>
>The wavelength of 2.4GHz is:
> 3*10^8 meters/sec / 2.4*10^9 Hz = 0.125 meters