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.
In the Matter of
An Inquiry Into the Commission's Policies and Rules
Regarding AM Radio Service Directional Antenna Performance Verification
MM Docket No. 93-177 SECOND REPORT AND ORDER AND SECOND FURTHER NOTICE OF
PROPOSED RULEMAKING
Adopted: September 24, 2008 Released: September 26, 2008
Comment Date: (30 days after date of publication in the Federal Register)
Reply Comment Date: (60 days after date of publication in the Federal Register)
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.
I leave to others to calculate what their antennas and towers will require.
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.
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