Antenna Construction Accuracy

Archived from groups: alt.internet.wireless (More info?)

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.

--
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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Archived from groups: alt.internet.wireless (More info?)

On Fri, 17 Dec 2004 00:09:36 -0800, in alt.internet.wireless , Jeff
Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:

>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>

Reply to Anonymous

Archived from groups: alt.internet.wireless (More info?)

On Fri, 17 Dec 2004 00:09:36 -0800, in alt.internet.wireless , Jeff
Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:

>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>

Reply to Anonymous

Archived from groups: alt.internet.wireless (More info?)

> 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.

Reply to Anonymous

Archived from groups: alt.internet.wireless (More info?)

On Fri, 17 Dec 2004 00:09:36 -0800, in alt.internet.wireless , Jeff
Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:

>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>

Reply to Anonymous

Archived from groups: alt.internet.wireless (More info?)

Mark McIntyre <markmcintyre@spamcop.net> wrote:
>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...

Reply to Anonymous

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