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[DPRG] Did you test real distance of RF communication (BlueTooth, Wi-Fi, ZigBee)?

Subject: [DPRG] Did you test real distance of RF communication (BlueTooth, Wi-Fi, ZigBee)?
From: Kipton Moravec kip at kdream.com
Date: Mon Sep 3 15:28:02 CDT 2007

RF distance specs are almost always wrong.

The high frequencies blue tooth and WiFi use do not go through brush,
trees and leaves very well. They do tend to go through holes and reflect
off of metal objects better than lower frequencies.

The little walkie-talkies that are FHS and GMRS advertise 14 or 17 mile
range. I was able to squeak out about 1850 yards in one case. They are
very environment dependent. 

I had a 2.4 GHz system go 2.6 miles with no directional antenna through
trees and corn fields. The only thing I could figure out was the signal
bounced off of a water tower.

A 1/4W 900 MHz system was able to reach about 1/2 mile where the company
told us 7 miles. We told them our results and they redid their test and
got the same as we got.

At Amateur Radio Field Day we had a WiFi link easily go a mile using two
directional antennas. And we will do the same at the Plano Balloon
Festival the third weekend in September. Except this time we have one
antenna on a church with Internet connection, and 4 directional antennas
pointing towards it across the Balloon Festival field. 

Another test we got better range in one direction than the other. We
switched antennas, transmitters, and cars with the same results each
time. We determined their was more RF noise at one location, and the
receiver could not work as well there. In a less noisy RF environment
(the other end) we got better range.

There is a lot more to RF communications than hooking up to modules and
see what they will do.  There are a lot of things you can do to improve
your range. Height above the ground is the easiest. Directional antennas
are also a good idea. What are you doing about earth ground?


On Mon, 2007-09-03 at 21:34 +0400, Oleg Lioubtchenko wrote:
> Hi,
> Recently we did some tests on the fields of some typical Bluetooth and
> Wi-Fi devices.
> We found that real outdoor range is much shorter then range from the
> specification. 
> Real distances  were:
> Bluetooth Class 1 devices: 16-50 meters (not 100 meters). 
> Wi-Fi was able to work in a distance 132 meters (not 300 meters).
> Have you ever done such a tests? 
> Test details:
> http://www.RoboHobby.com/range_of_bluetooth_and_wi-fi_connections.jsp
> Sincerely, Oleg
> -- 
> http://www.RoboHobby.com - Java brain for your small hand-made J2ME
> robot, based on cell phone (Siemens S75) with camera.
> _______________________________________________
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Kipton Moravec KE5NGX
"Always do right; this will gratify some people and astonish the rest."
--Mark Twain

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