In today's designs there is typically a RF switch prior to the radio - it
rapidly samples both antennas and selects the one with the strongest signal.

Very cheap!

Simon


-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Greg Troxel
Sent: Thursday, December 11, 2003 12:40 PM
To: Jim Thompson
Cc: Greg Troxel; Fred Weston; [EMAIL PROTECTED]
Subject: Re: [BAWUG] Question about antenna diversity 


  In most implementations, there is no 'summing', rather the "best" of
  the N (typically 2) antennas is fed to the baseband.

So there are 2 IF stages, with independent AGC-type detectors, and the one
with the stronger signal gets demodulated?

  > Another approach is to use a power splitter and put two antennas on
  > the primary connector.  This would bring the gain of the omni down by
  > 3 dB (plus loss of splitter and extra coax/connectors involved) and
  > then you could put a low-gain antenna on the other port.

  I'm not sure there is any system gain with this approach.

I didn't mean to claim there was.  This is simply constructing an antenna
pattern which is half of the high-gain pattern and half of a lower-gain
pattern, which might or might not have greater utility.  My understanding of
Fred's problem is that the signal level below the antenna is too low, and
that the antenna-centric solution is to fill in the sidelobes a little bit.
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