AM DETUNING FOR WIRELESS TOWERS

A detuned cellular monopole with a 5 tower protected AM station in the background

AM DETUNING FOR WIRELESS TOWERS

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Detuning FAQ’s

FCC Mandates AM Radio Protection by Antenna Owners/Licensees

Constructing a wireless telecommunications tower or other structure without appropriate steps to comply with FCC AM regulatory requirements can trigger construction delays, FCC violations, and costly penalties. The requirement to protect AM stations is found in 47 CFR Part 1-30002.

In general, all antenna support structures within one kilometer of non-directional, and three kilometers of directional AM stations must be evaluated. Both new construction and significant modification of existing structures must be considered. For FCC purposes, most building mounted antennas are not considered.

Not heeding FCC AM Compliance Regulations could mean that your tower or antenna structure could distort a nearby AM station’s signal pattern, triggering FCC penalties, civil liability, and/or zoning issues.

Why Wireless Licensees Must Protect AM Stations

Wireless antenna structures are typically steel, be it a tower, water tank, sign or other structure. The heart of the problem is that metal conducts and reradiates the AM radio waves in which it is immersed.

When the cellular tower is a significant portion of a wavelength in the AM broadcast band, significant mutual coupling occurs between the cell site structure and the AM tower. This mutual coupling induces AM RF power in the cellular tower which then will retransmit a portion of this AM power with an efficiency dependent upon separation distance, height, and AM frequency. Thus, the wireless tower effectively becomes another tower in the AM station’s system, changing its FCC licensed radiation pattern.

Interactions between AM antenna systems and cellular/wireless towers are becoming more common as the density of cell sites increases. This interaction is independent of the frequencies in use on the wireless tower, and relates solely to the proposed tower characteristic at AM frequencies (540 – 1710 kHz). Many AM radiation patterns are held to very tight tolerances, just a few per cent, and a deviation can bring the AM station FCC fines and worse.

FCC Required Actions to Protect AM’s

• Review all wireless antenna construction to determine its proximity to AM stations.
• Perform an engineering study to determine if detuning action is required If in FCC distances.
• Notify any affected AM stations, with an opportunity to comment.
• Install appropriate detuning equipment on the wireless structure, if required.
• Adjust detuning equipment for FCC rule compliance.
• Inspect and maintain detuning equipment for the life of the structure.

DO I NEED IT?

How to Determine If Your Tower Requires Detuning

Use LBA’s free on-line AM Protection to determine what, if any, action might be required to be compliant with FCC Rules when an AM radio station is nearby. This free screening application evaluates your site for compliance with current FCC AM regulations.

Where the AM Protection Tool determines that no AM Compliance action is required you will immediately be issued a free AM Certificate of Compliance.

If the AM Protection Tool predicts FCC-prohibited interaction, the installation and adjustment of detuning equipment may be required to nullify the effect of the proposed telecommunications structure. In that case, LBA will advise you what remedial actions you must take.

In all cases where the AM Protection Tool determines that the proposed construction will be within the FCC-specified protection distances with a potential impact; each affected AM station must be notified. The construction proponent must make this notification to inform the AM station how it proposes to protect their antenna pattern. Notifications are a service available from LBA.

The AM Protection Tool is conveniently available on line, for fast, free, one-off screenings, However, LBA will also perform no charge bulk screenings of larger numbers of structures from your spreadsheets or other media. Please contact us directly for this service.

AM Collocation – A Profitable Alternative to Detuning

You, too, can find the gold in AM tower steel! It’s a win – win for both AM station owners and wireless carriers.

Now AM collocation is practical! LBA is the expert with over 30 years' experience in successful AM tower sharing. With over 10,000 AM towers in the US, a major resource in the site acquisition/zoning battle can be available to you. Directional or non-directional, virtually all AM towers become colocation candidates with our proprietary solutions. Learn more at HERE.

LBA SERVICES?

LBA Provides Full AM Detuning Protection Services

With LBA’s proven approach, unsurpassed hardware, and on-cost/on-time turnkey performance it is the nationwide leader in AM protection. LBA has been providing AM Compliance services, and designing and manufacturing AM detuning equipment specifically for wireless since the beginning of the cellular era.  We have over 50 years of AM and FCC experience, including some of the most complex broadcast detuning projects ever!

Typical AM protection services include:

• FCC compliance screening
• Issuing and tracking notification letters
• Computer modeling with NEC, as needed
• Negotiating compliance between carriers, broadcasters, and site designers
• Provision of detuning hardware and installation supervision
• Adjustments, performance verification, and reporting

CLIENTS WE SERVE

Virtually all major tower companies, wireless carriers, and many broadcasters have relied on LBA for on time, in budget performance of thousands of AM detuning installations and services.

 Complete references available on request

FREQUENTLY ASKED QUESTIONS

More about AM and protection

What is my responsibility as a wireless licensee to AMs?

When constructing or modifying a telecommunications tower in the vicinity of an AM broadcast station, the communications licensee has the responsibility to prevent or correct disturbances to the AM station antenna pattern from that construction which causes operation outside the radiation parameters specified by the FCC.

Powerline towers, water tanks, signs, flagpoles and other antenna support structures are included. Even antennas on wood poles must be considered because the power, lightning grounds, and transmission lines to the antennas are conductive and potential reradiators.

Presently, the FCC does not require consideration of antennas mounted directly to buildings.

What is a “significant modification” of an antenna structure?

Significant modification can simply be the addition or removal of lines and/or antennas on a tower or structure that has AM detuning hardware installed on it. Significant modification can also be the addition or removal of lines and/or antennas from an existing tower or structure that does not have AM detuning hardware installed on it, but is within FCC distance parameters relative to an AM station and/or the height of the tower is proposed to be extended by a specified amount.

How does the LBA AM Protection Tool work?

Our proprietary algorithm is based upon actual measurements of hundreds of similar towers, integrated with current FCC AM protection criteria, to predict what actions must be undertaken. This algorithm references an FCC-linked database of the current licensed parameters of all AM radio stations in the United States. This ensures the most economical resolution of AM detuning issues.

Does AM Protection only apply to cellular systems?

No, the FCC requires that antenna supporting structures for all licensed services must observe AM protection rules. This even applies to other AM, FM and TV broadcast stations!

Why is AM protection really necessary?

The AM radiation pattern of an AM station is authorized and licensed by the FCC after careful consideration of the location and patterns of other AM stations at or near the same frequency. The impact of a distorted pattern can cause interference to other stations. Distortion can also reduce the market coverage area of a station, thus affecting its revenue earning capabilities. This is a particularly sensitive issue since there is so much competition in AM markets.

AM antenna coverage patterns are vulnerable to distortion from “reradiators” located near their transmission towers. Because of the relationship between the height of typical wireless towers and AM signal wavelengths, FCC licensees are required to carry out AM protection actions when building or locating on a tower or tall facility near AM towers.

FCC Rules require that licensees “determine whether the [tower] construction or modification affected the AM station antenna pattern.” The implication is that there is concern about any effect on the pattern, and AM stations are often held to 0.5 dB tolerances in their pattern limits!

What steps should I take to ensure AM protection?

A coordinated program should be established to screen all telecommunications towers for AM protection liability. Optimizing the placement of towers relative to AM towers is necessary. When possible, one should use AM towers as host platforms for additional antenna systems. A competent and experienced professional that provides a full range of AM protection and detuning services is your most valuable asset in meeting the FCC mandates.

LBA’s years of experience can take you through AM detuning painlessly. As a first step, use the free LBA AM Protection Tool to screen your prospective towers or mods. Then, our consultants can assist you in creating a protection plan. 

Is "detuning" always required?

No. Frequently tower detuning is not required in order to adequately protect the nearby AM. Alternative procedures can be employed that satisfy due diligence requirements. The free LBA AM Protection Tool will give you the answers, and even issue you a free certificate if action is not required.

How can I put a wireless antenna tower really close to an AM tower?

Through careful engineering evaluation of the AM station’s licensed pattern, an optimum location can be found for a tower, even within an AM tower array. This provides a very strong advantage for licensees who are in need of an antenna site in areas that are challenged with zoning restrictions.

Can we really collocate on an AM tower?

Yes! The FCC permits collocation on “hot” AM towers. Wireless antennas and lines can mount directly on an AM tower with proper planning and equipment. AM towers are particularly desirable for location of remote radio head (RRH) systems. Learn more about AM colocation here. 

Is maintenance of AM detuning equipment required?

Yes. The FCC mandates continued testing and maintenance of AM detuning systems. Please check out our convenient guide to best practices in AM detuning maintenance at our blog.

Where can I procure detuning systems?

LBA is the only supplier of AM detuning services to also supply and commission all the detuning and colocation equipment needed to implement such systems. LBA equipment is patented and proprietary, proven in thousands of installations worldwide. It is used by virtually all major cell carriers and tower companies.

Are AM detuning systems energized and hazardous?

It is possible for high levels of AM RF energy to exist on towers close to a hot AM tower. In evaluating detuning issues, LBA typically seeks to identify potential RF safety issues. Also, where very high RF levels exist, LBA detuning systems are built to handle these high RF currents. It is always best to have a consultant, such as LBA, who is familiar with high RF power to ensure that safety and power capability are planned for. Some practical guidelines for working around detuned towers with high RF can be found here.

What other resources does LBA offer?

If you would like to read more about this topic, LBA has published a number of articles and White Papers on the subject. You might find “13 New FCC AM Protection Rules you Need to Know” very helpful. In this article we’ve taken complex FCC Regulatory language and boiled it down to solid short reference to the FCC AM protection rules. Use “detuning” in our search box for much more information on our site.