DISTANCE REQUIREMENTS:

If you build or modify a tower within 3.2 km of a Directional AM station or
within 1 km of a Non-Directional AM station you are required by the FCC to
do a partial "proof of performance" before and after a construction or
modification of a tower.. A partial proof is defined as the measurements of
8 points on every radial that appeared on the original proof when the
station first went on the air. If a station has 10 radials,
that would be 80 points or street intersections that has to be
measured before and after construction (160 points total). Then the two sets
of measurements are compared to each other to determine if any re-radiation
has taken place.

If the AM station has 10 radials Day 10 radials Night that would be 160
points for the before construction measurements, 160 points for the afters.
Total of 320 street intersections. Each AM station is different. Some have
2 patterns that need to be measured, some have one. Some stations have 8
radials (minimum), some have 18.... It depends on how many towers they are
using to broadcast their signal.

ARTICLES FROM FCC REGARDING DISTANCE..

http://www.fcc.gov/mb/audio/decdoc/letter/1997--10--02--tower.html

The above link is a letter from the FCC to Misty Jennings of SWB (now
Cingular) that discusses the Federal Governments Rules as they apply to
Cellular Companies and the construction and modification of their towers
next to AM stations.

(Similar Articles Below)
http://www.fcc.gov/mb/audio/decdoc/letter/1987--08--11--tower.html
If construction is planned with 2 miles (3.2 km) of a directional AM
array...

Same article was republished in 1989....
http://www.fcc.gov/mb/audio/decdoc/letter/1989--11--14--tower.html
Common Carrier Public Mobile Services Information

TO DETUNE OR NOT TO DETUNE:

Sometimes the cell tower is built inside the "major lobe" or the direction
the most AM signal is sent. If you build inside the major lobe the AM signal
will bounce off the tower and distort the signal. To prevent that we
sometimes recommend that a detuning skirt be installed. The skirt would
allow the signal to go around the tower instead of bouncing off it. We will
determine if detuning is necessary when we screen your site.

We don't sell detuning skirts but we can recommend someone that does.
Nott Ltd. Their phone number is 505-327-5646 fax 325-1142. They will
need to know the frequency you will be protecting (kHz) .

You can have the antenna installation crew install the skirt while they are
climbing the tower. The skirts usually run about $5000.
(www.nottltd.com ) info@nottltd.com

Two other companies that sell detuning skirts are:

Phasetek Inc.                                 Kintronic Labs
550 California Rd. Unit 11             PO Box 845
Quakertown, PA 18951                Bristol TN 37621
Phone: 215-536-6648                    Tel: (423)878-3141
Fax: 215-536-7180                        Fax: (423)878-4224
http://www.phasetekinc.com/        http://www.kintronic.com/
hotam@phasetekinc.com               ktl@kintronic.com
 

YOUR IN-OFFICE VERIFICATION OF CLOSE-BY AM STATIONS

If you go to the FCC webpage http://www.fcc.gov/mb/audio/amq.html
1. Scroll to the blue section at the bottom....
2. Click on the check box next to: "3.2 km radius for 22.371 & 73.1692"
3. Then type in your Lat and Long
4. Scroll to the bottom of the page and click on the "Submit" button

The FCC's webpage will give you a list of AM stations in the area that you
need to measure.

TO I HAVE TO MEASURE IF I ADD ANTENNA'S ON A BUILDING?

You are not required to measure when you co-locate on buildings..
(i.e. you cannot detune a building) Losses are very high in short towers
because of ground system resistance loss.  Figure-8 in the AM Rules
shows the curve for antenna radiation efficiency stops before 31 electrical
degrees [or 0.09 wave.]  This is 50 feet at 1700 -- the highest AM frequency.
From a practical sense, billboards and light poles not exceeding 50 feet
have never proven to be a factor around an AM station. Based on the
Figure-8 curve, the [then] Southwestern Bell Mobile Systems legal
department set a minimum height to measure (always notified) above
50 feet.   In the Chicago area, they used lots of short billboards for fill-in
sites and this rule saved them hundreds of thousands of dollars.  You are
required to measure the AM station if: You add antennas to a 50-foot or
taller flagpole, watertower, telephone pole, or new tower.  It is the coax
line running up and down the structure that creates re-radiation...
 

THE MODIFICATION ARGUMENT:
(DO YOU HAVE TO MEASURE CO-LOCATIONS?)
 

We recently inquired to the FCC about their definition of
"modification of a tower" in Rule 73.1692

Is it..
a) Co-location on a cell tower next to an AM
b) Co-location on a cell tower with a detuning skirt
c) Adding antenna height

On March 12, 2002 I had a conversation with Ed Lubetzky of the Audio
Services division of the FCC. His understanding of the rules was that AM
measurements must be made if you "change the re-radiation property in any
way". He felt measurements would only be needed in a case of co-location
with a detuning skirt where the re-radiation was already a problem. He
didn't specify if tower height was included in the modification rule. He also said,
" I will have to defer to my supervisor's interpretation of the rules."

I spoke to with Sun Nguyen, the HEAD of the Audio Services Division, on
Sept 13th. He says that modification COULD include co-location on a cell tower
WITHOUT a detuning skirt. Sun said, "It is a case by case basis, some cell towers,
if they are close enough to an AM station that is running high power, could be
effecting the AM stations pattern by a co-location on a non-skirted tower."

He did not specify what is "high power", what is "close enough".

So what is the solution? You can do one of two things:

1.) Measure an AM Partial Proof everytime you co-locate on a non-detuned
tower.
2.) Co-locate on a non-detuned tower and wait for the station to complain.

I wanted very much to get a definitive answer from the Head of the Audio
Services, but there doesn't see to be one. So it becomes a legal liability
issue. Will the AM station have a case to sue the cell company if the AM
pattern is out and the cell company didn't measure after each co-location?

I would forward this section to your regulatory legal department and ask
them to set up a company standard. It is important to remember, that if
partial proof AM signal measurements have NEVER been done on a tower
you are co-locating on, you are open to future protest and a fine. ALWAYS
make sure the tower owner has a proof on file.

STANDARD PROCEDURES:

The standard steps for keeping AM fires off your desk...

1. Screen all sites for AM and detuning issues (we do this for free). And
request an Estimated price of the work. (we provide this with the
screening).

All we need to screen a site for AM and detuning issues is :

Site Name or Number:
Lat:
Long:
Tower Height:

2. Set a construction date 30 days away from the time of the screening, so
if AM measurements must be made, there will be time

3. Submit a request for a Purchase Order Number once the candidate is a
confirmed "to be built" candidate.

4. Notify our office of the Purchase Order Number you have received so that
we can begin. (We will order maps, notify the station, and measure the
station's broadcast signal).

5.Order a detuning skirt (if one is needed)

6. Confirm that the "before construction" measurements are done so that you
can build.

7. You install the detuning skirt (if one is needed)

8. Call us to confirm that the tower is up and the skirt is installed.
(Please provide a combination to the fence surrounding the site so we can
adjust the detuning box)

9. Receive your AM proof of performance by FedEx. (Our company will send one
to the station)

The FCC can fine you for the following things:

a) Failure to notify
b) Failure to measure.
c) Failure to maintain detuning equipment (this usually gets disturbed
when a co-location takes place)

The fines run from $5,000- $20,000 and you are still required to measure and
detune if necessary.

THE ACTUAL FCC RULES:

To see the actual rules FCC rules just scroll down.

These are for Title 47, Sections 73.154, 73.1692 and 22.371

**********************************************
[Code of Federal Regulations] [Title 47, Volume 4] [Revised as of October 1,
2001]
From the U.S. Government Printing Office via GPO Access [CITE: 47CFR73.154]
[Page 40-41]
TITLE 47--TELECOMMUNICATION
CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION (Continued)
PART 73--RADIO BROADCAST SERVICES--Table of Contents
Subpart A--AM Broadcast Stations
Sec. 73.154 AM directional antenna partial proof of performance
measurements.

(a) A partial proof of performance consists of at least 8 field strength
measurements made on each of the radials that includes a
monitoring point. If the directional pattern has fewer than 4 monitored
radials, the partial proof shall include measurements on those radials from
the latest complete proof of performance which are adjacent to the monitored
radials.
(b) The measurements are to be made within 3 to 15 kilometers from the
center of the antenna array. When a monitoring point as designated on the
station authorization lies on a particular radial, one of the measurements
must be made at that point. One of the following methods shall be used for
the partial proof: (1) Measurement points shall be selected from the points
measured in
latest full proof of performance provided that the points can be identified
with  [[Page 41]] reasonable certainty, and that land development or other
factors have not significantly altered propagation characteristics since the
last full proof. At each point, the licensee shall measure directional field
strength for comparison to either the directional or the nondirectional
field strength measured at that point in the last full proof. (2) In the
event that a meaningful comparison to full proof measurements cannot be
made, the licensee shall measure both directional and nondirectional field
strength at eight points on each radial. The points need not be limited to
those measured in the last full proof of performance.  (c) The results of
the measurements are to be analyzed as follows.
Either the arithmetic average or the logarithmic average of the ratios of
the field strength at each measurement point to the corresponding field
strength in the most recent complete proof of performance shall be used to
establish the inverse distance fields. (The logarithmic average for each
radial is the antilogarithm of the mean of the logarithms of the ratios of
field strength (new to old) for each measurement location along a given
radial). When new nondirectional measurements are used as the reference, as
described in paragraph (b)(2) of this section, either the arithmetic or
logarithmic averages of directional to nondirectional field strength on each
radial shall be used in conjunction with the measured nondirectional field
from the last proof to establish the inverse distance field.
(d) The result of the most recent partial proof of performance measurements
and analysis is to be retained in the station records
available to the FCC upon request. Maps showing new measurement points,
i.e., points not measured in the last full proof, shall be associated with
the partial proof in the station's records, and shall be provided to the FCC
upon request.
 

[66 FR 20756, Apr. 25, 2001] Code of Federal Regulations] [Title 47, Volume 2]
[Revised as of October 1, 2001]
From the U.S. Government Printing Office via GPO Access [CITE: 47CFR22.371]
[Page 137-138]
TITLE 47--TELECOMMUNICATION
CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION (Continued)
PART 22--PUBLIC MOBILE SERVICES--Table of Contents
Subpart C--Operational and Technical Requirements
Sec. 22.371 Disturbance of AM broadcast station antenna patterns.
 

Public Mobile Service licensees that construct or modify towers in the
immediate vicinity of AM broadcast stations are responsible for measures
necessary to correct disturbance of the AM station antenna pattern which
causes operation outside of the radiation parameters specified by the FCC
for the AM station, if the disturbance occurred as a result of such
construction or modification.
(a) Non-directional AM stations. If tower construction or modification is
planned within 1 kilometer (0.6 mile) of a non-
directional AM broadcast station tower, the Public Mobile Service licensee
must notify the licensee of the AM broadcast station in advance of the
planned construction or modification. Measurements must be made to determine
whether the construction or modification affected the AM station antenna
pattern. The Public Mobile Service licensee is responsible for the
installation and continued maintenance of any detuning apparatus necessary
to restore proper non-directional performance of the AM station tower.
(b) Directional AM stations. If tower construction or modification is
planned within 3 kilometers (1.9 miles) [[Page 138]] of a directional AM
broadcast station array, the Public Mobile Service licensee must notify the
licensee of the AM broadcast station in advance of the planned construction
or modification. Measurements must be made to determine whether the
construction or modification affected the AM station antenna pattern. The
Public Mobile Service licensee is responsible for the installation and
continued maintenance of any detuning apparatus necessary to restore proper
performance of the AM station array.

[Code of Federal Regulations] [Title 47, Volume 4] [Revised as of October 1, 2001]
From the U.S. Government Printing Office via GPO Access [CITE: 47CFR73.1692]
[Page 314-315] TITLE 47--TELECOMMUNICATION
CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION (Continued)
PART 73--RADIO BROADCAST SERVICES--Table of Contents
Subpart H--Rules Applicable to All Broadcast Stations

Sec. 73.1692 Broadcast station construction near or installation on an AM
broadcast tower.

Where a broadcast licensee or permittee proposes to mount a broadcast
antenna on an AM station tower, or where construction is
proposed within 0.8 km of an AM nondirectional tower or within 3.2 km of an
AM directional station, the broadcast licensee or permittee is responsible
for ensuring that [[Page 315]] the construction does not adversely affect
the AM station, as follows:
(a) Installations on an AM nondirectional tower. During installation of the
broadcast antenna and related equipment, the AM station shall determine
operating power by the indirect method (see Sec. 73.51). Upon the completion
of the installation, antenna impedance measurements on the AM antenna shall
be made, and, prior to or simultaneously with the filing of the license
application covering the broadcast station installation, an application on
FCC Form 302-AM (including a tower sketch of the installation) shall be
filed with the Commission for the AM station to return to direct power
measurement. (b) Installations on an AM directional array. Prior to
commencing construction, the broadcast permittee or licensee shall notify
the AM station so that, if necessary, the AM station may determine operating
power by the indirect method (see Sec. 73.51) and request special temporary
authority pursuant to Sec. 73.1635 to operate with parameters at variance in
order to maintain monitoring point field strengths within authorized limits.
Both prior to the commencement of construction and upon completion of
construction, a partial proof of performance (as defined by Sec. 73.154)
shall be conducted to establish that the AM array has not been adversely
affected. Prior to or simultaneously with filing of the license application
to cover the broadcast station construction, the results of the partial
proof of performance shall be filed with the Commission on Form 302-AM. (c)
Tower erections or modifications within 0.8 km of an AM nondirectional
tower. Prior to commencing the construction of tower modifications, or the
erection of a new tower, within 0.8 km of an AM nondirectional tower, the
broadcast permittee or licensee is required to notify the AM station so that
the AM station may commence determining operating power by the indirect
method (see Sec. 73.51). The broadcast licensee or permittee shall be
responsible for the installation and
continued maintenance of detuning apparatus necessary to prevent adverse
effects on the radiation pattern of the AM station. Both prior to
construction of the tower modifications and upon completion of construction,
antenna impedance measurements of the AM station shall be made. In addition,
sufficient field strength measurements taken at a minimum of 10 locations
along each of 8 equally spaced radials, shall be made to establish that the
AM radiation pattern is essentially omnidirectional. Prior or simultaneously
with the filing of the application for license to cover this permit, the
results of the impedance measurements and the field strength measurements
shall be filed with the Commission on FCC Form 302-AM for the AM station to
return to the direct method of power determination. (d) Tower erections or
modifications within 3.2 km of an AM directional station. Prior to
commencing construction of tower modifications, or the erection of a new
tower structure, within 3.2 km of an AM directional array, the broadcast
permittee or licensee shall notify the AM station so that, if necessary, the
AM station may determine operating power by the indirect method (see Sec.
73.51) and request special temporary authority pursuant to Sec. 73.1635 to
operate with parameters at variance in order to maintain monitoring point
field strengths within authorized limits. The broadcast licensee or
permittee shall be responsible for the installation and continued
maintenance of detuning apparatus necessary to prevent adverse effects upon
the radiation pattern of the AM station. Both prior to the commencement of
construction and upon completion of construction, a partial proof of
performance (as defined by Sec. 73.154) shall be conducted to establish that
the AM array has not been adversely affected. Prior to or simultaneously
with filing of the license application to cover the broadcast station
construction, the results of the partial proof of performance shall be filed
with the Commission on Form 302-AM.
[62 FR 51062, Sept. 30, 1997]
 

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