I'd add two commments to Scriv's post...
1) The requirement may vary significantly on wether one is using a Omni or
Sector. When using an Omni, a filter becomes the only method to solve the
problem, since it can't be solved with Antenna isolation strategies
(shielding/front to back).
2) Filters fit real nicely into WaveRider's product, since Waverider already
have COAX fed antenna ports, and a ground base station unit, requiring Coax
up the tower already.
Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
----- Original Message -----
From: "John Scrivner" <[EMAIL PROTECTED]>
To: "WISPA General List" <[email protected]>
Sent: Friday, October 27, 2006 9:09 AM
Subject: Re: [WISPA] Sprint / Nextel to use 900mz for iDen
If you have an adjacent channel carrier which is running hundreds of watts
of power then you may not have a choice of whether to use the bandpass
filter or not. Your system may not operate in the upper part of the 900
MHz band. What happens is that the adjacent carrier will "swamp" your
receiver and your base station will essentially become deaf to your own,
much quieter, client radios. The bandpass filter is the sole remedy to
this. I think many people use filters by default because they do little
harm to your system performance and may mean the difference between your
system working or completely failing in the presence of higher-powered
adjacent carriers.
I currently run Waverider 900 MHz systems and because of this I may have a
system which is more sensitive to adjacent carrier swamping than other
platforms. I simply do not know about other platforms to say one way or
another. I believe Charles has tested several 900 MHz platforms and may be
able to expand on this discussion. It is important to note that he may
have a bias toward Canopy as he now sells that platform. I can only assume
that his testing may have led him, in part, to this platform choice for
900 MHz systems. Care to share your thoughts Charles?
If anyone out there has any past experience with swamped 900 MHJz
receivers, bandpass filters, different 900 MHz platforms, etc. then please
share your thoughts about the use/need for bandpass filters. I would like
to know more myself.
Scriv
Larry Yunker wrote:
While filters can help, the problem that I see is that filters are: 1)
expensive and 2) bulky. Last time I checked, a cavity filter for the
902-928 range was roughly $300-$400. I don't see it being practical to
install one of these at every customer site!
Cavity filters are fine for your broadcast sites, but that is of little
help when the 900Mhz paging systems bleed over so much that they "deafen"
the subscriber radios.
- Larry
----- Original Message ----- From: "Mike Cowan"
<[EMAIL PROTECTED]>
To: "WISPA General List" <[email protected]>
Sent: Thursday, October 26, 2006 7:32 PM
Subject: Re: [WISPA] Sprint / Nextel to use 900mz for iDen
Filters fix this problem quite handily. We recommend one on every
system needed or not. I don't see an issue here.
Mike
At 07:07 PM 10/26/2006, you wrote:
ISM 902-928.
Exact band and Power limit is relevant. Currently, the top 25% of ISM
900 bandwidth (channel 4) is unusable, in MANY areas, due to blead over
from 930 Licensed high power gear (500W). If the same thing were to
occur at the lower portion of 900 ISM bandwdith, it could kill Channel
1 also, horribly effecting WISPs using unlicenced. They also may be
requesting to use higher power on the actual ISM bands, argueing Public
Safety is more important than unlicensed use. Iftheir request is
granted, specifics should be lsited on how they are going to prevent
interference with existing unlicensed band users. Remember that the
goal may not only be to use the spectrum. They have benefit in killing
off all the 900Mhz WISPs, that could compete with Sprint/Nextel Next
generation WiMax type Licensed 700M-900M solutions.
Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
Mike Cowan
Wireless Connections
A Division of ACC
166 Milan Ave
Norwalk, OH 44857
419-660-6100
[EMAIL PROTECTED]
www.wirelessconnections.net
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