AM Tower Collocation Introduction

AM radio broadcast towers are rapidly becoming the new “hot topic” in the wireless communications industry. The name of the game today for wireless carriers and tower owners alike is “colocation, collocation, co-location” on existing structures. To date, this has not necessarily included attachment to an existing AM radio broadcast tower, even though there are an estimated 10,000 AM towers in existence in the United States. In many locales, new site opportunities are becoming stressed, leaving AM towers as strategic, or often, the only possible locations for new site opportunities. Even where open sites exist for new towers, local zoning and planning authorities often require that all collocation options be exhausted before “Greenfield” towers are permitted.

This places AM tower owners directly in the path of economic opportunity. How much opportunity? In many locations, cellular and PCS antenna locations rent for about $2500 per month. If four tenants can be attracted to an AM tower, that’s potentially a $10,000 per month revenue stream. Even better, the wireless carriers typically pick up the costs of tower modification and on-going maintenance!

To tap this pot of gold, it’s important to understand how AM tower collocation works from a carrier perspective, and what you, the AM broadcaster, must consider to present a viable site opportunity to the wireless industry.

Why Not AM Tower Collocation?

Historically, the wireless industry has been warned to stay clear of AM radio stations at all costs. This not only had to do with attaching to them, but also with reference to locating nearby and interfering with their broadcast patterns. Indeed, wireless carriers must prove to the Federal Communications Commission that they have considered and corrected all such problems when constructing or modifying any tower within three kilometers of an AM station. This has left underserved “holes” around many AM’s, often in prime suburban areas.

In the past, AM towers were considered unsuitable for antenna attachment by most cellular and PCS wireless carriers due to presumed grounding difficulties, interference and safety considerations. Coordinating construction between the vastly different AM and wireless cultures was frequently a slow and painful process. From an engineering perspective the process of integration and demonstrating license compliance to the FCC often required tinkering, delays and costs unacceptable to wireless carriers and broadcasters alike. AM station owners have also wanted assurance that the tower collocation methods proposed by the wireless operator were reliable, proven, and acceptable to the FCC and would not harm their signal coverage pattern. In the past, these outcomes could not be readily or easily assured. Many wireless system designers, and AM tower owners themselves, are yet unaware that new technologies are now available to solve these problems and efficiently integrate wireless and AM systems at reasonable costs.

In the AM band, the tower itself is the radiating element without a need for attached antennas. However, wireless antennas and coaxial cables are self-contained systems that merely attach to their support structures. Achieving compatibility with the AM tower through electrical integration or isolation of wireless antennas is a challenging engineering exercise. Since AM broadcasting is a specialized field, many wireless system designers and constructors, not being conversant with lower frequency technology, have been unaware of the techniques available to make wireless compatible with AM. Few broadcast engineers and consultants have experience in tower collocation, except for the odd STL or FM standby antenna. Thus, many potential AM tower collocations have been avoided as technically impossible or prohibitively expensive. Sometimes large additional costs have even been incurred for detuning the resulting new tower near the avoided AM station!

The solution to these problems is actually straightforward in most cases, and can be readily implemented at reasonable cost by using a qualified consultant and the latest hardware solutions.