Cavity Filters create several additional problems....
1) Assuming most filters are narrow individual channel widths... It takes
away the benefit to move your Radio Freq Channel to stear around
interference on the fly.
2) Assuming 1 Filter covers the full width of the Band... The filters add
significant loss, 3-4 db, so channels 1,2,3 that may not need the filters
get compromised, just to save channel 4. In this business every DB counts.
3) Most filters get installed on the ground, where they can easilly get
power and not need water proofing, then requiring large COAX runs to create
additional signal loss. However, assuming one has a tower mountable unit,
Many CAT5 powered 900M Radios, have the Antenna's built in, with no Coax
option to install the filter on.
4) What we found worked best was to use very high grade Sector antennas w/
higher front to back ratios and sharper cut offs (which is hard to
accomplish with NLOS 900M, but are a couple brands that accomplish this).
These antenna get rid of most of the AP side colocation interference, near
equivellent to the filter. Although the filter did a bit better on AP side,
it was counter-acted by reducing signal several DB, having negative effects
on gaining the required signal based on interference and NLOS foliage
degrading CPE signal. And of course combine this with good radios with
built-in noise reduction.
With that said, I'm not saying a filter can't help in all cases, thats what
they were designed for, to help. My point is that the benefit starts to be
diminished signifantly compared to the cost. This issue is overyly
burdensome to the provider. So the last thing we want to see happen is it
get re-created on lower bands of 900Mhz. (iDEN ?)
As far as filters.... If someone wanted to buy one, its a more complicated
task than one always realizes. Cavity filters, notch filters, saw filters,
Custom built, etc, what to get, and where to buy? Do you have
recommendations on which Cavity Filters to use, for outdoor tower mounting?
Or do you use the ones that WaveRider sold?
Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
----- Original Message -----
From: "Larry Yunker" <[EMAIL PROTECTED]>
To: "WISPA General List" <[email protected]>
Sent: Friday, October 27, 2006 9:25 AM
Subject: Re: [WISPA] Sprint / Nextel to use 900mz for iDen
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
--
WISPA Wireless List: [email protected]
Subscribe/Unsubscribe:
http://lists.wispa.org/mailman/listinfo/wireless
Archives: http://lists.wispa.org/pipermail/wireless/
--
WISPA Wireless List: [email protected]
Subscribe/Unsubscribe:
http://lists.wispa.org/mailman/listinfo/wireless
Archives: http://lists.wispa.org/pipermail/wireless/
--
WISPA Wireless List: [email protected]
Subscribe/Unsubscribe:
http://lists.wispa.org/mailman/listinfo/wireless
Archives: http://lists.wispa.org/pipermail/wireless/
