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Selecting a transmission site

Let's assume that you've allocated money for a new transmission site and it is time to apply for a construction permit. Or, as is increasingly becoming the case, the real estate around the old site has become as valuable, or more valuable than, the station itself. In any case, the time has come when you must find a new place for the tower.

Map it out

A good way to start is to have the station's consulting engineer prepare a map showing the limits on the site based on spacing to other stations, allocations or applications. A fully spaced site is preferable because it results in the cleanest application. Yes, there are ways to overcome some short spacing, but they require more extensive engineering showings, they open the door to the possibility of objections to the application, and they may limit the station's facilities.

After struggling with aeronautical and station-spacing issues, KMOS selected a site 55 miles away from its Warrensburg, MO, studios for its new 2000-foot tower.

You should then transfer the spacing map to a large-scale map of the area topography. That allows you to analyze natural terrain obstructions that would limit the actual service of the station. Obviously, you shouldn't put a station in a location where high terrain exists between the site and the city of license. If possible, you should select a site where you can use natural terrain elevation to offset tower height above ground level. These facts would seem to be obvious. But, amazingly, some site-location decisions have been made more on the basis of saving a few bucks than on the long-term performance of the station.

Now that you have determined possible sites based on spacing requirements and topography, you need to identify any aeronautical considerations. In an area where there are few airports or none at all, this can be quite simple. You also need to consider the proposed height of the tower. For a very tall tower, the aeronautical considerations are usually too difficult for the average station engineer to calculate. In such cases, you can hire one of several good firms to prepare a detailed study of the factors that may limit tower height, such as airways, instrument-approach areas or visual flight paths. As a general rule, it is difficult to get FAA clearance for a tower more than 500 feet above ground level within two miles of an expressway or other significant landmarks for pilots flying under visual flight rules, including cross-country transmission lines, rivers, railroads or main highways. The decision to grant clearance in such cases is often a judgment call best made by someone experienced in flight patterns and FAA policy.


After the spacing, topographic and aeronautical considerations have all been drawn on the same map, if you are lucky there will be some areas left where you can locate the tower. You may not like these areas, but they are places where you may have a chance of getting a site that will work and be acceptable to the FCC and FAA. Now it's time to visit those areas, look for available property and evaluate the local conditions. For example, you should try to find property where three-phase power is already available. Running in new three-phase power can be prohibitively expensive. If your station's power demand isn't excessive, it is possible to generate three-phase power using a UPS system that will accept single-phase power input and provide three-phase power output. An alternative is to use electro-mechanical converters that generate three-phase power from a single-phase source. When connecting equipment to such a converter, some special considerations apply to avoid damage from transient conditions. Using a UPS after such a converter will eliminate those problems.


The ugly issue of zoning will probably come up at some point in your study. Although a recent court ruling may lead to some relaxation in zoning limits on towers, it is best to try to find a site where zoning is appropriate for towers or where approval seems reasonably possible. Usually, that means land zoned for agricultural or industrial use. Certainly, try to avoid land that is zoned strictly for residential use. The first step is to visit the local zoning authority to find out what their requirements are and to get some guidance as to how to proceed with your zoning requests. Another source of help would be a local attorney who practices or specializes in zoning and real estate.

Buy or lease?

Now it is finally time to start talking to land owners to nail down a site. The most desirable option is for the station to actually purchase the land. While site ownership is more expensive initially, it can help you avoid problems years down the road, especially if the value of the property goes up due to area development.

If possible, select a site where you can use natural terrain elevation to offset tower height above ground level.

But rural landowners seem to like to maintain ownership and are more likely to agree to a long-term lease. By long term, we mean at least 20 years, with options to extend the lease in 20-year increments for at least another three or four terms. Usually, such agreements are for a fixed annual rate that is adjusted annually based on the cost-of-living index. This is fair to all because it keeps the real cost the same as time goes by, regardless of the value of the dollar. In agricultural areas, the ground that a farmer leases for a tower site yields the best cash crop for the whole farm.

A solid foundation

If more than one good site is available, look at the soil properties of the site itself. The civil engineering types are great at being able to design a system of foundations and guy points that can cope with about any situation. The problem is that the more exotic schemes are usually significantly more expensive. The preferred situation is good solid soil conditions with enough room to guy the tower at 80 percent of its height. If the space is smaller than that, you can bring the guying down to 50 percent of height without prohibitive costs. Guying distances shorter than that will raise the price significantly and you should avoid them if at all possible.

To determine the actual foundation and guy point design for a large tower, it is advisable to have someone perform soil borings to analyze the existing conditions. This usually involves a boring at the tower base and one at each guy-point location. You can find companies that do this under civil engineering or soil testing in the phone book. The tower manufacturer should be involved in this process to ensure that everyone is on the same page in the design of the total system.

Finally, during tower construction, it is a good idea to have concrete samples taken and tested to ensure that they comply with the specifications listed in the foundation designs. Common practice is to take two samples from each load of concrete delivered to the site. After the samples have aged, usually for at least 28 days, an independent laboratory should test the samples. If the lab finds that some of the concrete was bad, the contractor should remove and replace the foundation or guy point involved. Obviously, no contractor wants this to happen. We are talking about some serious expense here.

Don Markley is president of D. L. Markley and Associates, Peoria, IL

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