[TowerTalk] Antennas and towers near broadcast stations

[Its from Onion]

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.