[VHFcontesting] Re: [VHF] Cell Sites

[John Allen]

Roger et al - Please be aware of the different bands used, based on the cell
company and the technology that they use.

Cingular, AT&T and others are using GSM/GPRS/Edge/UMTS (Coming) on 1920-1980
MHz paired with 2110 to 2170 MHz. (known as the 1.9 GHz. band).  The other
bands are 850, 900,  and 1800 MHz.  I don't think that 900 is used in the
USA.

73, John, K1AE

John Allen  - PC Support Solutions www.pcsupportsolutions.com
PC House Calls: Computer HW/SW/Network debugging, installation, maintenance,
and upgrades
mailto:john at pcsupportsolutions.com  978 779-6189 M: 508 361-6229

-----Original Message-----
From: vhfcontesting-bounces at contesting.com
[mailto:vhfcontesting-bounces at contesting.com]On Behalf Of Mike Clarson
Sent: Friday, October 08, 2004 10:17 AM
To: 'jeff millar'; w3sz at comcast.net
Cc: 'VHF Contesting'; vhf at w6yx.stanford.edu
Subject: RE: [VHFcontesting] Re: [VHF] Cell Sites


Jeff: Most of the new cellular equipment is pretty good, but the older
analog (particularly AT&T series 2) would wipe out low end of 902 band. I
would be a little more cautious than saying "I wouldn't worry about TX noise
from the transmitter". There can be a lot of RF around cell sites. I say
worry, but it is almost always fixable, so it shouldn't be a deal
killer.--Mike, WV2ZOW

-----Original Message-----
From: vhfcontesting-bounces at contesting.com
[mailto:vhfcontesting-bounces at contesting.com]On Behalf Of jeff millar
Sent: Thursday, October 07, 2004 10:16 PM
To: w3sz at comcast.net
Cc: VHF Contesting; vhf at w6yx.stanford.edu
Subject: [VHFcontesting] Re: [VHF] Cell Sites


Roger...

A neighbor (David, wb1cmg) went through this.  He had 180 ft of Rohn 45
and the cell company wanted to get on it.  They uprated the guy anchors,
installed new larger guys, built a road and building. They installed
three sectors at the 120 ft level.  Dave gets the top.  My 440 repeater
sits on that tower.  Dave is active on all VHF, UHF and microwave band
and has not had interference, even on 900.

I know from experience that cell transmitters use bandpass duplexers
with very high rejection of out of band signals.  I wouldn't worry about
TX noise from the transmitter.  They're somewhere around 870-890 MHz and
probably have a TX noise level of -40 dBm prior to the filter, then the
filter rolls off at about 30 dB per 5 MHz.  Assuming worst case band and
Tx carrier placement, the filter will still have about 60 dB of
rejection by 902/903.  Then add 60 dB of antenna to antenna isolation
and the noise floor in your 900 Rx probably runs -160 dBm.  These
numbers are familiar to me because the company I work for designs Cell
systems and has to deal with our potential to generate intermods and Tx
noise in the public safety band and other frequencies.

If you want to test this, drive up close to a cell site with a yagi and
Rx and check for a noise rise when you point at the antenna.  You won't
see any.

Dave talked the cell company into increasing the size of the building
and giving him the use of half...but they did use his tower.

The going rate for this is between $1000 and $2000 per month.  Don't let
them short you.

jeff, wa1hco



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