Jim,
I echo feelings that sectors and an in depth look at the spectrum
already in use in the areas you wish to serve. You must become familiar
with your landscape. Sometimes hills that block signals can be a good
thing because they also block a lot of interferences. 900MHz tends to
travel 50 or more miles unobstructed. I use those hills to cover small
60-90 degree wedges that would have otherwise been reachable because of
the same hills Water tanks have been helpful to fill in areas but my
greatest success has come from towers twice the distance or more above
treetops. My coverage area is very hilly with a lot of trees.
I have been happy using WaveRider gear and the filters designed for
their systems. It's more expensive using towers because of coaxial cable
costs, but I also don't have to climb a tower to fix a radio problem. As
I've deployed on water tanks in the area our costs are less than
Motorola Canopy systems and we have more channel choices - 7 verses 3 or
4 for Canopy I think. Canopy systems use an 8MHz wide channel, whereas
WaveRider uses a 5.5 MHz channel and others as low as 5MHz. Of course
the top and bottom channels 905 and 925 can become unusable in many
environments because of paging and cell systems. I've been able to
structure my sectors that we can use them anyway. We use a mix of
horizontal and vertical polarization base station antennas. We use Antel
antennas - watch the numbers they measure power in dbd verses dbi. As a
rule of thumb you add 2.1 to dbd to estimate dbi. I have recently tried
Tiltek and PacWireless antennas but will go back to Antel for our future
deployments. Again more expensive than others but my experience says
they are worth it. Adjacent transmission sites get opposite polarity
antennas and as much separation between channels as I can get if they
point at each other or can be seen by each other. On some transmission
sites I use 3 - 120 deg sectors, others maybe a 180 deg and a 90 or two
90's, I have one site with one 120 because that's all I needed to cover
and when you use multiples transmitters on a site you need separation
between channels. I'm not all that familiar with Motorola gear but
others on the list are. They have a GPS sync function that allows them
to reuse more channels throughout their network. I don't want to start a
feature / religious war about brands but these are my 5 plus years
900MHz experiences. I've found no two sites are anywhere near the same
as I've designed and built my system from the center out. We now operate
more than 20 transmission sites around a county in southern Indiana. I
have 12-15 more to go before we cover 95% plus of the people and we'll
probably get there this year. I will say that WaveRiders throughput is
more limited 2 MB verses 6MB for Canopy. In my area that hasn't been an
issue yet. I have heard of an 8MB POE transmitter due out this summer.
Maybe Scott Carlson, who is a vendor member, would like to comment. grin.
I've have tested Canopy, Trango, Tranzeo, and Ubiquiti cards and without
filters none will work very well. Without filters noise floors can be
80db or less. With filters and the right design you can get better than
90db in most cases. I've tried entire band filters 902-928 and found
them to be mostly ineffective in eliminating the noise from pagers and
cells sites. The biggest problem I see in looking at Tranzeo, and
Ubiquiti, other than the later isn't certified, is the lack of filter
availability. WaveRider's filters are centered around the channels they
support and that's made all the difference for us. Some of our sites
were designed to transmit 3 miles because that was our target, others
are designed to go 8 miles because that was our target. Your maximum
power output is 4 watts or 36 EIRP but you don't always have to put out
that much power, sometimes less is better.
My disclaimer. I don't own or have interest in any of the companies I've
discussed other than my own. Just my thoughts.
Good Luck,
Dave Hulsebus
Portative Technologies
Corydon, IN
www.portative.com
Message: 6
Date: Sun, 8 Apr 2007 10:14:14 -0500
From: "Jim Stout" <[EMAIL PROTECTED]>
Subject: [WISPA] 900 MHz Help
To: "WISPA General List" <wireless@wispa.org>
Message-ID: <[EMAIL PROTECTED]>
Content-Type: text/plain; charset="iso-8859-1"
Folks,
I'm just entering into the 900MHz space and would appreciate any advice on channel selection and channel width settings.
TIA, Jim....
Jim Stout
LTO Communications, LLC
15701 Henry Andrews Dr
Pleasant Hill, MO 64080
(816) 305-1076 - Mobile
(816) 497-0033 - Pager
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