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February 2, 2006, 1:35 pm
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I have been gathering information on Homebrew Wireless Antennas and have
made a couple as an experiment.
Basically its for accessing my wireless network from my garage which is some
My latest one out of a Mini Cheddars Can seemed to work well, I think.
I have been measuring the signal strength using Net Stumbler but I am a bit
confused and need some quick pointers.
I understand that signal strength and Noise is measured in dBm and think
from what I have read on the Antenna Shoot out that the lower the dBm the
Netstumbler shows a graph with a left hand Axis that shows the Signal
Strength and Noise according to the help file the signal strength should be
in green( The higher up the graph the better, higher up the scale the lower
the dBm reading) and noise in red if available.
My graph only shows a green bar so I guess thats signal strength.
Last night while testing my PCMCIA card only I got a signal strength of
about 60 dBm when I attached the Antenna I got about 40 dBm (Wrote it down
somewhere) if that is the case I just increased my signal dramatically.
I know it got better because when accessing my Network the wireless networks
Icon increased from 36Mbps to 54Mbps.
Does anyone know of a software tool for bechmarking or measuring wireless
signal strengths in order to accurately record results.
Re: Wirless Antennas
for numbers, say a transmitter is producing 1 watt of
power to a standard
antenna, increasing the gain of the antenna by
10db will increase the power by
10 times, so a 1 Watt TX feeding a
aerial with a 10db gain will give the same
signal strength as a 10
Watt TX with a standard aerial say a quarter wave or a
The way to add gain to an antenna is to 'beam' the signal in the
direction rather than radiate the power in un-wanted
directions, this can easily
be done with a beam or yagi antenna as
they are called,.
I would imagine a
Corner reflector type antenna would be most
suitable, these are simply a dipole
place behind a reflective plate
either solid or meshed, the size of the plate,
the spacing between
the aerial all have effects on the matching impedance and
reflector resembles a letter 'V' on its side with the dipole mounted
horozontally, these antennas gain give quite a fair amount of gain
One of these at the receiving end will increase the sensitivity
likewise, you can get info on these antennas from Radio Ham books
like the ARRL
or RSGB books.
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