I am dissapointed that just as things were getting interesting, Harris
prism chipset was newly issued and the power output from the PCI4800
cards went down to 30 mW from 100 mW. Which is significant since I use
them always almost in WAN applications. But I am confused by the
4800B sensitivity at 5.5 Mb/s is -87 dBm, whereas 4800 is -83 dBm (so
4800B is more sensitive by 4 dBm). And of course the power output is
less by 5 dBm from 22 dBm (4800B < 4800 power output). So, just how does
the "the power reduction is a loss of 5 dB for you, sensitivity is a
loss of 3 dB" statement fit.
would that not be: a LOSS of power output by 5 dBm, while a GAIN of
sensitivity by 4 dBm, so therefore, the link budget using a 4800B
compared to a 4800 would be equiv. of a LOSS of 1 dBm ???
By the way isn't -5 dBm equivalent to 0.316, so... would 5 dBm reduction
in the RF power output level mean that the previous power output of 100
mW is now.. 31.6 mW ?
I guess, 1 dB = 10 * log (Pi/Po) comes in handy.
I'm defintely not a mathematics person, and have never studied
electrical engineering and by all means am a layman when it comes to
analog radio black magic and RF power ... mea culpa in advance if I
screwed up but I would surely like to know where I did and how I can
learn my mistake and use the 4800B cards in a better fashion.
> Date: Wed, 16 Feb 2000 19:24:06 -0800
> From: Jean Tourrilhes <jt@...>
> To: Elmer Joandi <elmer@...>
> Cc: aironet@...
> Subject: [Aironet] Re : Aironets power & sensitivity
> For the Aironet 4800B :
> -90 dBm @ 1 Mb/s
> -88 dBm @ 2 Mb/s
> -87 dBm @ 5.5. Mb/s
> -84 dBm @ 11 Mb/s
> Tx power : 30 mW = +15 dBm
> Old aironet cards are at :
> For the Aironet 4500/4800 :
> -93 dBm @ 1 Mb/s
> -90 dBm @ 2 Mb/s
> -83 dBm @ 5.5 Mb/s
> -80 dBm @ 11 Mb/s
> Tx power : 100 mW in FCC (but only 50 mW in ETSI versions)
> So, the power reduction is a loss of 5 dB for you, sensitivity
> is a loss of 3 dB, so you link budget is reduced by 8 dB. What is the
> cost and the size of an antenna giving you an additional 8 dB gain ?
> At 11 Mb/s, the gain in sensitivity offset the loss of power.