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InGreenwood to shoe1
Anon
2008-Feb-17 11:13 am
to shoe1
Re: 10-15 mile Wifi possible cheap? legal?said by shoe1:And I want to stay 100% legal too. Does that include not asking your friends to violate their TOS with their DSL ISP? Assuming you are buying DSL and just need it extended, your first cost will be to build masts that get you LOS with a fresnel zone above the tree tops. » en.wikipedia.org/wiki/Fr ··· nel_zonesaid by shoe1:The connection can be extremely directional. Two of these would get you started, although I would be amazed if you really only needed 2 feet of cable at each end if you need a mast to get above trees. » cgi.ebay.com/Home-Networ ··· ViewItemsaid by shoe1:What are the FCC regulations in California? Same as the rest of the US, so far as I know they have not seceded or been thrown out of the US. |
actions · 2008-Feb-17 11:13 am · (locked) |
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Using that yagi would violate FCC rules as it is not tested and approved with that router.
Any length of coax would negate the gain of the antenna.
Rain on the antenna elements would reduce gain considerably as well. At 2.4 GHz, the elements need to be protected by a radome. Even at 900MHz, yagis are affected by rain.
For the distance needed, outdoor radios should be used and there are many avialable with approved high gain antennas but they will break the $300 budget. Just getting up above the trees in itself, will break the budget. |
actions · 2008-Feb-17 11:32 am · (locked) |
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Should antennas then be placed inside a buildings attic as to protect them from rain? is rain hard on the antenna or just the signal? |
actions · 2008-Feb-17 2:19 pm · (locked) |
·Metronet
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to InGreenwood
quote: Does that include not asking your friends to violate their TOS with their DSL ISP?
Can be legal as far as the ISP goes - several do allow folks to share the connections even if they are not part of the household/house. Most do not allow it - but a couple do. |
actions · 2008-Feb-17 3:26 pm · (locked) |
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to Ledebuhr1
Yagi antennas have finely tuned elements that get detuned when water drops change their resonant length. This is a very different phenomenon than airborne rain affecting the signal. |
actions · 2008-Feb-17 4:05 pm · (locked) |
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Here's the laws-of-physics / engineering on 10-15 mi with "wifi"... 1) Most ill-advised at 2.4GHz due to high user density = lots of interference, though highly directional antennas such as wire-mesh parabolics (like these: » www.hyperlinktech.com/we ··· 424g.php and » www.hyperlinktech.com/we ··· 2dbi.php) will help a lot. Still, users in the near vicinity of either end will be a problem if those users are active. 2) 802.11b/g is a 20MHz bandwidth (wide) signal. The narrower the bandwidth, the less noise. Less noise = more range, in general. Less bandwidth means lower bit rates and speed, usually, but new technologies like 802.16e with "real" MIMO and adaptive rate modulation and beam-steered antennas can eek out lots more speed for the same bandwidth. Kinda like in automobile engines: horsepower per cu. inch has gone way up due to better designs. |
actions · 2008-Feb-17 7:04 pm · (locked) |
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The local school board had a 13 mile link on Cisco 2.4GHz gear for years before switching it over to Tsunami on 5.8GHz. Of course they had tall towers at both ends to clear the fresnel zone. |
actions · 2008-Feb-17 7:37 pm · (locked) |
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yes, long paths over hills or urban clutter = tall towers to get Fresnel zone clearance as shown in the graphic, above.
Size of zone varies with frequency - higher = easier. Path loss per Km increases with frequency too! But antenna size reduces as freq. increases. Bigger = more gain, as a general rule.
If you have enough antenna gain, you can work out a link budget that can tolerate some blockage of the Fresnel zones. |
actions · 2008-Feb-18 2:18 am · (locked) |
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said by stevech0:If you have enough antenna gain, you can work out a link budget that can tolerate some blockage of the Fresnel zones. Yes, in the plot I posted there is not a clear fresnel zone because of the trees. I have the option in RM of showing all the fresnel but I chose only to show .6 which many consider the minimum for long shots. The tree height (only estimated) leaves a possible .9 fresnel. Higher frequencies have smaller fresnel zones but also have greater free space loss. |
actions · 2008-Feb-18 8:55 am · (locked) |