Antenna Construction Accuracy

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Jeff Liebermann 21 years ago

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

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.

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Dave VanHorn 21 years ago

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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W

William P.N. Smith 21 years ago

In radio, 1/4-wave _is_ the antenna length, not the tolerance...

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Mark McIntyre 21 years ago

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.....

This would certainly be very nice tho... :-)

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M

Mark McIntyre 21 years ago

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.....

This would certainly be very nice tho... :-)

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M

Mark McIntyre 21 years ago

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.....

This would certainly be very nice tho... :-)

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Antenna Construction Accuracy

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