This is a compilation of the responses that I received regarding the
placement of cell towers on our building. I only received two responses
from NMR labs that have cell towers nearby and neither has seen any
problems that they would connect to the cell towers. It is too difficult
to try to define each nuclei observed on each site, at each static
magnetic field, the type of cell system and the power levels inside of the
lab but all of that data would be needed to make a solid comparison.
Alltel has done a site visit to familiarize themselves with our operation
and to demonstrate the existing back ground in the 834 MHz region.
There has been widespread alarm within the department over the idea. I
would prefer that the antennas (all transmission antennas for that matter)
not be located anywhere near us but given that the next best building is
only a few hundred feet away and given the fact that Alltel's preferred
orientation would put us in the maximum transmission path of one of those
antennas I might prefer to be behind them rather than in front of them.
The directionality of these antennas is such that the signals are about 30
to 40 dB or better down at nearly all positions behind the plane of the
antennas. Additionally as oppose to a centered pole mount they are looking
at a roof edge mount which does put us well behind all of the antennas.
My only experience with the FCC so far was when a local CB operator was
operating an illegal booster amp (he said so over the airwaves). It was
coming through demodulated on my TV, my stereo and my cordless phone. The
FCC "offered to help" but only after I could give them his call sign and
prove that he was over power and they suggested that I would not only need
a spectrum analyzer but also a calibrated antenna. Unlike the CBer Alltel
stands to lose a lot if they are out of FCC compliance so I would hope
that their filtering and power calibrations would be good.
With regards to corrupting our power and grounds they told me that they
run dedicated lines back to the transformer and that they drive a
dedicated earth ground 20-30 feet into the ground. The also filter the AC,
which does work both ways, it protects us from them and them from us.
On a surprising point to me they run liquid helium cooled filters and will
have a setup very similar to the cryo probe as far as having a cold finger
and compressors and all.
No matter what due diligence is done I anticipate that the day after it is
installed it will become the blamed source for nearly all electronic
problems in the building.
If this does go through I will post a follow-up.
Joe Dumais
------------------------------------------------------------------------------------------
We have cell antennas on our roof, 3 floors directly above the NMR lab.
We've never noticed an effect on our 300, 400, or 500 MHz spectrometers.
--------------------------------------------
No experience with cell phones, but the use of rf seems to be increasing
exponentially. You might be better off just biting the bullet start
putting
in faraday cages. There is a copper "wallpaper" that can be put over
dry wall, but copper/brass screen would probably cost less.
----------------------------------------------------------------------------------------
I'm not experienced with your situation, but I would think the FCC
provides some regulatory protection against the phone co. adding
interference to your labs. The problem is that they are not likely to
care until after the fact, when you'll have to show evidence of the
interference.
In addition to the carriers transmitting directly into the grounds and
filtration designed into your consoles, their digital modulation will make
a symphony of noise. The effect might not be immediate, but eventually I
would guess you'll have problems with birdies and sidebands in the data as
the components of your systems age under the stress. If it were one of my
labs, I would ask them to install a grounded foil shield in the ceiling,
so my RF lived under an umbrella from theirs. Actually, I wonder why they
are not concerned with you transmitting interference to them. The noise
from the experiments in your consoles might easily fall into their band,
and your transmitters are just as big as theirs. If the situation becomes
adversarial, just tie an efficient antenna to the console instead of a
probe, and BLAST 'em! The FCC might even provide you a convenient
'experimental' or 'research' exception to normal rules for transmitters
that the phone company does not have the luxury of.
----------------------------------------------------------------------------------------------------
We just had a cell tower installed on our building last summer, and they
didn?t even tell us they were going to do it. We found out after the
fact. They just invaded the labs that were in the path of the cables, and
installed the equipment unannounced!! So, at least they are giving you a
heads-up there.
We have seen no ill-effects in any of our instruments from the cell tower
on our building, but (of course) you are much closer to the antenna. The
upside is that our T-Mobile customers can actually get a maxed-out signal
in the basement NMR labs, while the rest of us barely get any cell signal
at all in the basement :o).
I don?t think you?ll have any trouble, but if you force their hand, and
make them stick it on top of Oldfather, then I?m sure you won?t have any
problems we are closer to our tower in our basement (only 3-stories in the
chem building here) than you would be to Oldfather.
-----------------------------------------------------------------------------------------------------
Hopefully you would have an 'Esc key' if it didnt work out to your liking.
Joe Dumais, Ph. D.
Associate Research Professor
Director of Research Instrumentation Facility
Department of Chemistry / University of Nebraska Lincoln
834 Hamilton Hall / PO Box 880304
Lincoln, NE 68588-0304
Phone (402) 472 6255 / Fax (402) 472 9402
http://www.chem.unl.edu
Received on Fri Apr 22 2005 - 17:45:24 MST