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
w3sz wrote:
Hello, All,
I am asking for advice from the collective wisdom of the VHF and
VHF-Contesting lists.
I have been approached by a cellular company wanting to put up a tower
on my property and of course to lease that space.
My immediate response on reading the letter was, "Are you crazy?" I
had this response of course because of concerns about EMI in both
directions, me to them and them to me.
I am however by virtue of the fact that my property is quite high,
and probably sees every cell tower for more than 10 miles in all
directions already exposed to multiple cell towers, at least a couple
of which are fairly close [I would guess on the order of 0.5 to 1.0
mile away, but that is just a very rough guess]. I have a few bleeps
and bloops on 903, but that is it in terms of problems as far as I
know. I am not aware of any desensing on the other bands {I operate
50 MHz thru 24 GHz weak signal terrestrial, and 144 MHz EME}. I use
cavity filters before the preamps on 144 MHz EME, and helical filters
on 50 thru 903 MHz before the preamps.
The amount they offer as a starting point for negotiation is not
large, but it would cover my property taxes and in addition leave me
with more money to spend annually on ham radio than I would
ordinarily allow myself to spend. So I am starting to consider this,
thinking that maybe suffering some additional bleeps and bloops on
903 would be a small price to pay for the financial benefits of such
an arrangement. My wife of course thinks this is a good deal, and
has already figured out that if I do this it will be 'x' years before
the rent we receive from the deal will pay off what I have already
spent on ham radio-related expenses I have incurred at the property.
So there are domestic advantages to the deal. ;)
Other thoughts that occur to me:
1. No neighbor problems currently with my present towers. This
could potentially cause some I would think. And if I don't do the
deal, and make that known, it could be a positive if complaints ever
surfaced.
2. If the cellular signals are strong enough, I could suffer
significant problems on other bands [besides 903] due to mixing
products.
3. I don't know how MUCH rent / other benefits it is reasonable to
ask for. I faintly recall a QST article where I believe the author
got in addition to rent a new tower, antennas, maintanence, etc.
Does anyone have knowledge of the 'going lease rates', which I am
sure vary a lot? I am in Southeastern Pennsylvania.
4. I would need to have some agreement that the cell company would
need to accept any interference that occurred from me, with the worst
result allowed being that they would terminate the agreement. No
other damages allowed. And maybe they would have to leave the tower
in place if they left.
Any thoughts from those who have been down this road, or considered
it, or know someone who has, would be appreciated.
Thanks in advance, and
73,
ROger W3SZ
_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting
|