There are approximately 10,000 AM broadcast towers in the United States. Most are in ideal locations and just high enough to accommodate cellular antennas. However, few AM towers are also used for cellular towers. What's going on here?
Lawrence Behr, chief executive of the LBA Group, has said that AM broadcast and cellular communications are "a hundred years and 1,000 megahertz apart". Why? Because AM broadcasting is a technology that emerged nearly 100 years ago, operating at frequencies between 0.53 and 1.71 MHZ (530 to 1710 kHz), little has changed from its origins. By contrast, cellular and "wireless" systems mostly operate in the 700 to 6000 MHz range, and even new and more useful forms are still being developed.
Why is this important? Because of two main factors: power and antenna size. AM requires antennas a thousand times larger than cellular. AM may cover hundreds of miles, while a cell site is only a few miles. This requires far more power than cellular coverage, leading to perceptions of security risks.
The differences between AM and cellular are so great that few engineers and technicians cross over between technologies, and there is little crossover between business interests. In short, they don't talk to each other. But they should!
Many AM towers have been in the same location for 50 years or more, often in once rural areas that have now developed into densely populated suburbs. These areas are very difficult to sit for new wireless towers, but AM towers are "part of the community" and generally relatively uncontroversial about wireless configurations. That makes them very appealing to the wireless community -- aside from their "hot" and untouchable reputation. AM towers are a resource whose utilization of cellular colocation sites can serve the wireless industry while generating new revenue for unaffordable AM sites.
And, as we'll see, "hot" doesn't have to be a barrier to cellular hosting!
