Fixed Terrestial Wireless

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== Path Variables ==
== Path Variables ==
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=== Rain Attenuation ===
 
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With a radio path of less than 10 miles, the path should not normally be subject to too many variables.  Rain attenuation would not normally be a problem.
 
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=== Line of Sight ===
=== Line of Sight ===
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If you have line of sight, then trees or someone building and consequently obstructing the line of sight WOULD be a problem. If you don't have line of sight, then the path may still work, and may change with the seasons if trees are the reason for it not being line of sight.
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If you have line of sight, then tree growth or someone building and consequently obstructing the line of sight might well create a problem. If you don't have line of sight, then the path might still work, but might change with the seasons if trees are the reason for it not being line of sight.
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=== [http://en.wikipedia.org/wiki/Fresnel_zone Fresnel Zone Clearance] ===
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=== Fresnel Zone ===
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The remaining issue is one of ground clearance, commonly known as [http://www.afar.net/fresnel-zone-calculator/ fresnel zone clearance].  Fresnel zone clearance gives you an indication of what effect the ground along the path will have. If the path is very close to the ground, then you don't have much clearance, and will lose a few dB.  But the path should be stable.  If the path is high above the ground, and crosses over a flat area along the path that can be seen from the antennas at both ends, then you have the possibility of signal reflections off the ground arriving at the receive antenna delayed and out of phase with the direct path, and the two signals can cancel.  It is an unfortunate fact of life that the reflectivity of the ground can change drastically.  If you have a rough surface, or a nice crop of corn, it will attenuate any signal that would otherwise be reflected.  But at another time of year, the ground can be bare, maybe have a nice coating of dew or water, and be very reflective.  The solution to this type of problem normally is to alter the height of one antenna and change the reflection from a cancelling mode to an additive mode.  I suspect this is seldom done for this type of service.  Maybe this whole paragraph should be deleted.
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The remaining issue is one of ground clearance, commonly known as [http://www.afar.net/fresnel-zone-calculator/ fresnel zone clearance], which gives you an indication of what effect ground along the path will have. If the path is very close to ground, then you probably won't have enough clearance, and will lose a few dB, but the signal should be stable.
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The only good thing to know about this fresnel zone topic is that the path will normally be short enough you don't have to worry about [http://en.wikipedia.org/wiki/K-factor K] changing the fresnel zone clearance.
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=== Ground Reflection ===
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If the path is high above ground, and crosses over a flat area along the path that can be seen from the antennas at both ends, then you have the possibility of signal reflections off the ground arriving at the receive antenna delayed and out of phase with the direct path, and the two signals can cancel.  It is an unfortunate fact of life that the reflectivity of the ground can change drastically.  If you have a rough surface, or a nice crop of corn, it will attenuate any signal that would otherwise be reflected.  But at another time of year, the ground can be bare, maybe have a nice coating of dew or water, and be very reflective.  The solution to this type of problem normally is to alter the height of one antenna and change the reflection from a cancelling mode to an additive mode.
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=== Rain Attenuation ===
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With a radio path of less than 10 miles, the path should not normally be subject to too many variables.  Rain attenuation would not normally be a problem.
==Service Speeds==
==Service Speeds==
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===Typical===
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High speeds of 4.8 Mbps downlink and 1.8 Mbps uplink are quite possible. Actual speeds can vary greatly depending on provider, geography, and class (cost) of service.
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Since I have not had access to any hardware manuals, and I am writing this late at night, I will just offer up so observations.
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In my area at the current time, the data rate provided by my radio link is about 4.8 Mbps download, and about 1.8 Mbps upload. This can be controlled by the service provider by settings in the radio (I don't know which end) that pertain specifically to my link. This is about the same speed, if not faster, than I might get by a wired hookup by a cable or phone company provider.  Ones upload and download speed to the internet can be checked at [http://www.speedtest.net/ SpeedTest].
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Latest revision as of 21:36, 29 January 2010

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