Re: Longer legal links?

> How does having a more sensitive Rx antenna increase Tx range?

OK, basically, we're limited by a legal maximum transmit power of 20dB.
Most cards use the same antenna for transmit *and* receive.  By having a
transmit antenna and a receive antenna, you can increase gain on the receive
end, as this is not regulated by law.  The distance you can get a signal is
regulated by the number of decibels your link has.

For example, my card at home is a 15dB model, and has a 5dB antenna on it.
If two identical machines like this were setup, then there would be 15db +
5dB+ 5dB = 25dB in the link.  That's transmit power (15dB) + transmit gain
(5dB) + receive gain (5dB).  If
you can increase receive gain without increasing transmit gain, the numbers
will be higher, and therefore go further.

transmit power + transmit gain must be less than 20dB
transmit power + transmit gain + receive gain relates to distance
(bigger=further)

Also, there is leakage between the antennas, so there are other things to
consider which were explained in the previous mail.  It all boils down to
longer links whilst staying legal.

Andy