Mac,
Thanks for replying to my concerns and suggestions.
Have you tried using 5 to 10 feet of vertical separation between the
antennas rather than mounting them all at the same height? 10 feet of
vertical separation should be enough to prevent one AP transmitter from
overloading another AP receiver.
Secondly, single-channel bandpass filters are available which will
provide additional receiver protection from nearby transmitters
operating on non-overlapping frequencies.
Finally, higher-priced antennas normally have a higher front-to-back
ratio which increases isolation (minimizes interaction) between the
antennas. A minimum f/b ratio of 30 dBm is recommended.
Keep in mind that without dealing with these antenna isolation issues,
you will likely have the same problems using two 180* sector antennas as
you have had using three 120* sector antennas.
jack
Mac Dearman wrote:
See in line please
Behalf of Jack Unger
Mac,
Before you discard the idea of using three 120* sectors are you
absolutely certain that the "separation" issue is really due to the
antennas not being far enough apart? Have you thoroughly looked at other
reasons why there could be interference between three APs like:
[Mac says:]
Well Jack - I'd like to think that I have exhausted the other possibilities
:-) but I am always willing to listen.
1. Using three cards on a single motherboard in one enclosure without
sufficient shielding between them.
[Mac says:]
All of our sector arrays utilize 3 different enclosures with one radio to
the enclosure and then I try to separate the enclosures (and antennas) as
far as possible.
2. Using three APs that are configured on frequencies that are too close
together and are interfering with each other?
[Mac says:]
Unless we deploy 4 90* sectors we use non overlapping channels (1, 6 & 11)
I guess what I'm asking is (before you go spend money on antennas that
may or may not solve the problem) what equipment are you currently
using, how is it configured, and how far apart can you actually get
three sector antennas on the 25G tower?
jack
[Mac says:]
I have come to the conclusion that it is interference from the backplane of
the antennas due to not having adequate separation from each other. These
small towers (although 180') like Rohn 25G aren't but 12" across - so you
wind up with the 3 sectors only 1' apart at their bases.
I wish you had some more ideas :-), but thanks for the thought and the time!
Mac
--
Jack Unger ([EMAIL PROTECTED]) - President, Ask-Wi.Com, Inc.
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Serving the Broadband Wireless Industry Since 1993
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