Re: what's the difference between bluetooth and woreless?
- From: Paul <nospam@xxxxxxxxxx>
- Date: Mon, 11 May 2009 14:25:03 -0400
Robert wrote:
i have to buy a keyboard + mouse but i don't know what is the
difference between bluetooth and wireless: which one reaches the max
range? I need to get to 25 FT - 30 FT with a quite cheap price.
Wikipedia has articles on both technologies.
But what I cannot tell you, is all the methods that
keyboards use for communications. At least some of them,
work at 27MHz (CB band ?). Some work at 2.4GHz, which
is potentially in the same frequency range as Wifi.
Bluetooth also works at 2.4GHz. It operates
"frequency-hopping spread spectrum" over 79 frequencies
from 2.4 GHz to 2.4835 GHz. Devices come in three output
power levels. Class 1 is supposed to reach 100 meters.
But you're not likely to find Class 1 devices for just
everything - the lower power classes would be more common.
A keyboard manufacturer would probably reasonably assume
there is no reason to operate a keyboard at a 100 meter
distance from the computer screen.
http://en.wikipedia.org/wiki/Bluetooth
This is an article on Wifi. But what we don't know, is if a
keyboard operating in this frequency range, is compliant with
the methods used here or not. They could use an incompatible
method (amplitude or frequency modulation), and I don't know
what standards control what they do. I wasn't able to find
any examples of the silicon used to implement those keyboards.
http://en.wikipedia.org/wiki/802.11
"2.4000–2.4835 GHz band is divided into 13 channels each
of width 22 MHz but spaced only 5 MHz apart"
There is a picture in that article, how three wide channels
fit into the spectral space.
http://en.wikipedia.org/wiki/File:2.4_GHz_Wi-Fi_channels_(802.11b,g_WLAN).png
If I was attempting to do what you're trying to do, I'd look through
the Newegg listings of wireless keyboard products, then read the
customer review section, to find products with exceptional reach.
Once you identify a product with exceptional reach, you can shop
for a good price on it elsewhere. (If you shop locally, you can
even return it, if the reach is not sufficient. There can be
significant device to device variation in reach, and this
can be related to the quality of the RF implementation in
the device.)
There are also the security implications of wireless keyboards.
If you're in an apartment building, it might not be wise idea to
use a high powered device, and have a neighbor "pair" with your
keyboard. I don't know how secure a wireless keyboard would be
against snooping. Would a "Wifi keyboard" use WPA2 - probably
not. The communication is likely less secure than that, whatever
the method is. So again, broadcasting your password entry, for
someone listening with a radio receiver in the street, is probably
not the best idea.
There is also the interaction with other consumer goods in the
same household. For example, there are wireless phones that
operate at 2.4Ghz. So if you see weird things happen, like
the wireless keyboard stops working for an instant, check
out what other devices in the house, pollute the airwaves.
As you might guess from these comments, there is no wireless
in my house. Everything is wired.
Paul
.
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