[TowerTalk] antennas and towers near broadcast stations

[jim Jarvis]

Bottom post... see below:

(edited for space...)
Message: 6
Date: Fri, 13 Feb 2009 20:47:25 -0600
From: "Its from Onion" <aredandgold at 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