Bottom post... see below:
(edited for space...)
Message: 6
Date: Fri, 13 Feb 2009 20:47:25 -0600
From: "Its from Onion" <aredandgold@msn.com> Subject: [TowerTalk]
Antennas and towers near broadcast stations
The FCC has without much notice in Amateur circles passed was:
"quietly snuck," a poor choice of words, a Rule that will affect non-
broadcast radio licensees including Radio Amateurs.
excerpt:
Quote:
?1.30002 Tower construction or modification near AM stations.
(a) Construction near a nondirectional AM station. Proponents
of construction or significant modification of a tower which is
within one wavelength of the AM station, and is taller than 60
electrical degrees at the
AM frequency, must notify the AM station at least 30 days in
advance. The proponent shall examine the potential impact of the
construction or modification as described in paragraph (c). If the
construction or
modification would distort the radiation pattern by more than
2 dB, the licensee shall be responsible for the installation and
maintenance of any detuning apparatus necessary to restore proper
operation of the
nondirectional antenna.
(b) Construction near a directional AM station. Proponents of
the construction or significant modification of a tower which is
within the lesser of 10 wavelengths or 3 kilometers of the AM
station, and is taller than 36 electrical degrees at the AM
frequency, must notify the AM station at least 30 days in advance.
The proponent shall examine the potential impact of the
construction or modification as described in paragraph (c). If the
construction or modification would result in radiation in excess of
the AM station's licensed standard pattern or augmented standard
pattern values, the licensee shall be responsible for the
installation and maintenance of any detuning apparatus necessary to
restore proper operation of the directional antenna.
(c) Proponents of construction or significant modification of
a tower within the distances defined in (a) and (b) herein of an AM
station shall examine the potential effects thereof using a moment
method analysis. The moment method analysis shall consist of a model
of the AM antenna together with the
potential reradiating tower in a lossless environment. The
model shall employ a simplified version of the methodology specified
in ? 73.151(c) of this chapter. The AM antenna elements may be
modeled as a Federal Communications Commission FCC 08-228 series of
thin wires driven to produce the required radiation pattern, without
any requirement for measurement of tower impedances.
(d) A significant modification of a tower in the immediate
vicinity of an AM station is defined as follows:
(1) Any change that would alter the structure's physical
height by 5 electrical degrees or more at the AM frequency.
(2) The addition of one or more antennas or a transmission
line to a tower that has been detuned or base insulated.
(e) The addition or modification of an antenna or antenna
supporting structure on a building shall not be considered significant.
(f) With respect to an AM station that was authorized pursuant
to a directional proof of performance based on field strength
measurements, the proponent of the tower construction or modification
may, in lieu of the study described in paragraph (c), demonstrate
through measurements taken before and after construction that field
strength values at the monitoring points do not exceed the licensed
values. In the event that the pre-construction monitoring point
values exceed the licensed values, the proponent may
demonstrate that post-construction monitoring point values do
not exceed the pre-construction values.
Alternatively, the AM station may file for authority to
increase the relevant monitoring point value after performing a
partial proof of performance in accordance with ? 73.154 to establish
that the licensed radiation limit on the applicable radial is not
exceeded.
(g) Tower construction or modification that falls outside the
criteria described in the preceding paragraphs is presumed to have no
significant effect on an AM station. In some instances, however, an
AM station may be affected by tower construction notwithstanding the
criteria set forth above. In such cases, an AM station may submit a
showing that its operation has been affected by tower construction or
alteration. If necessary, the Commission shall direct the tower
proponent to install and maintain any detuning apparatus necessary to
restore proper operation of the AM antenna.
LINK<http://fjallfoss.fcc.gov/edocs_public/attachmatch/FCC-08-228A1.pdf>
A vertical resonant at 1.8 MHz is 81 degrees tall at 1.6 MHz and
would be if not detuned at the BC frequency forbidden within 2 miles
(approx) (or 10 wavelengths at its frequency if less) of a
directional AM station. An 80 meter vertical falls to it as well, as
well as many shorter towers according to their electrical length.
Considering the impact the unnoticed Part 73 action has had in
Amateur circles, a reconsideration could be in order if only to
accept our comments.
-0-
N2EA Comments: This is perfectly reasonable, on its face.
Commercial interests bear the responsibility of assuring
that their construction... towers or power lines, for example... do
not impact the pattern of a directional array AM station.
The cost of re-certifying a directional array... repeating the proof,
is something on the order of $20,000, in today's dollars,
before you add in the consulting engineer's fees. Been there, done
that, as they say. 4 times, in fact.
I had a 4 tower AM station go out of licensed Field Strength
parameters, and had to operate on waivers, for
over a year, until we identified a high tension line at 2 miles
distant as the offending construction. Lawsuit
followed. It was $100k legal fees, out of pocket, until the utility
in question lost, paid up, and detuned their towers.
Then, we had to repeat the proof of performance, which entailed
almost $20k in labor, plus a consulting engineer's
fee of 14k.
Like the idea that amateurs should be exempt from stupid driving
while distracted by our radios, we are not exempt
from causing inadvertent harm to commercial operations by our
construction. Much as we might like it to be otherwise.
Thoughtful consideration is in order, with all we do. (Like
climbing safely!)
I think the real concern here is cell towers, not us, just to be
practical. Oh, and just to crank a few numbers,
a wavelength at 1 MHz is 936'. 10 wavelengths is 1.8 miles. At
1.5Mhz, that's 1.2 miles. Odds of us affecting
them at that distance are quite small. But why should we be exempt,
if we cause harm?
If we make a vertical resonant on our operating frequency, it is, de-
facto, non-resonant at the broadcast freq.
i.e. decoupled. And we shouldn't have to worry.
Unreasonable rule making? I don't think so.
N2EA
Jim Jarvis, MBA, President
The Morse Group, LLC
www.themorsegroup.net
Leadership and Supervisory Development * Strategic Planning *
Corporate Coaching
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