[MLB-WIRELESS] [TIB] A new offer has been added to TIB - 11/1 2/2002

[Tony Langdon]

> you missed my point.
> 
> my point was that they don't increase the output *BY* 1 Amp.  they
> change it *TO* 1 Amp regardless of the input signal strength. 
>  i.e. it's
> *not* cumulative with the original Tx power.

Come on guys, let's at least get the termonoligy right! :-)  For a start,
power is measured in Watts, not Amps.  Current consumption is measured in
amps (more correctly called Amperes).

Now, an amplifier has what is called "gain".  Depending on the design of the
amplifier, this gain may remain relatively constant, regardless of input
level (in which case, the amplifier is said to be linear - hey, this is
where the CB term "linear" comes from!), or the gain may change with input
level (non-linear - common in FM transmitters because of their higher
efficiency).

Now, I'm no expert on 802.11b modulation techniques, so I don't know if the
power amplifiers are linear or not, but I do know that if you vary the
drive, you WILL vary the output in some way (tuned up enough transmitters to
know that one :) ).

However, some amplifiers may have automatic power control, so the power is
limited to the rated output over a wide range of drive level.  Again, I do
not know.

At this point, we need someone who actually knows specifically about 802.11b
amplifiers.

> > No, they amplify the signal and noise alike... They don't increase
> > sensitivity, if anything they reduce it due to increased noise...
> 
> some claimed to increase sensitivity.  whether that's truth 
> or marketing
> lie is something that testing would tell.

This depends on two things.  Firstly, the noise figure of the receive
preamplifier in the unit.  If it has a lower noise figure than the input
stage of the wireless card, you will generally get some improvement in
sensitivity.

Secondly, where you place the amplifier will have a big impact.  If it has a
receive preamplifier, then locating it as close to the antenna as possible
means that the receive signal gets amplified before the lossy coax.  This
can make a considerable improvement to the received signal.  This is the
same principle between masthead preamplifiers in TV and amateur radio
installations - put the gain before the lossy feedline.

So on the question of receive improvement, the true answer is "it depends".
:)

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