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There are more new AMs than FMs for many good reasons.
First of all, due to the need for ground radials, a new AM station requires a good chunk of real estate. Double, triple, or even quadruple the real estate required if that station needs two or more towers for a directional array.
This makes AM much more expensive. Not only do you need the real estate, but you need to buy and bury all those radials, adding extensively to the cost again. Not to mention the potential cost of ssveral towers.
With FM it’s very likely that tower space can be leased, and towers are often shared with many other entities. The FM station I work for shares it’s transmitter site and tower space with the local public station (we lease from them). That one tower holds the array for two different 100,000 watt FM stations (them on 91.7 and us on 96.9) as well as STL receiving antennas for both stations, AND the ham radio clubs repeater antennas (three). This is because, of course, the FM tower is just a supporting structure, whereas the AM tower IS the antenna. AM towers very rarely are able to play host to any other devices. Although it *can* be done, it’s expensive and can play havoc with the AM stations pattern. FM also eliminates the need for all those buried radials, eliminating the need tor all that real estate.
In addition an FM transmitting antenna can often be added to an existing structure, especially in the case of translators and LPFM. We have several water towers with translator and TV repeater antennas on them.
Additionally clearing the necessary enviromental hurdles is a heck of a lot easier for one FM tower than several AM towers.
Just a few reasons why the new stations are on FM. Also, it’s pretty rare when the occasion comes along to get a chance to file for a construction permit for a new AM station.