[asterisk-biz] looking for Wifi Ip Phones

[trixter aka Bret McDanel]

On Fri, 2006-09-15 at 20:05 +0800, Dinesh Nair wrote:
> 
> On 09/14/06 21:44 trixter aka Bret McDanel said the following:
> > that with a 802.11b/g device which uses the same set of spectrum, given
> > how close the BT and wifi antennas would be to each other would cause a
> > dramatic reduction in range from the AP due to desensitizing the
> > antennas of the other rf unit.
> 
> that would explain why the 802.11 range on the nokia e-series phones suck 
> big oranges. however, would this still be the case if bluetooth was turned 
> off in the phone ?
> 

it shouldnt, when you have 2 antennas really close on similar
frequencies basically one overpowers the other and think of it this
way ...

in a large open building (gymnasium for example) if you are next to one
person talking to you and someone is at the other end talking you will
hear the one next to you and only maybe be able to faintly make out the
guy at the other end.  If the person at the other end is really loud or
has a reall distinct voice you can hear em better.

Its kinda like that for radio devices, the guy next to you desensitizes
your ear from the guy all the way at the other end, so he either has to
yell or he has to have a higher/lower pitched voice for you to hear (the
pitch being similar to a really different frequency).

In addition if you are in a gymnasium with a ton of people all chatting
away, you can hear the people near you, but there is so much noise that
you cant hear anyone that far away.  And generally you have to be closer
to whomever you want to hear (relative power is stronger) to hear them
and understand what they are saying.  That is like having a ton of
devices all on the same frequency, and the effects on range are similar.

With radios you have 2 properties (which unfortunately arnet disclosed
enough).  Sensitivity and selectivity.  Sensitivity is how faint of a
signal can be 'heard' and selectivity is how well the radio can
distinguish one signal from another that is close in frequency.
Generally if you have one that is really good, the other suffers.  

When I speak of 'desensitizing' a radio, its the sensitivity property
that I speak of.  When the antennas are close to each other the relative
power that is received on the other is so high that it kinda overdrives
the front end of the radio and causes it to not be able to tell that
signal from another. 

This is akin to having someone stand next to you yelling in your ear
while you try to listen to someone a little distance off.


-- 
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