This section of the website deals with the issues of LPFM engineering. Basically, the FCC's LPFM decision allows the licensing of low power FM facilities throughout the FM band (88.1-107.9 MHz) using a powers of 1-100 watts (that which we generally think of as "LPFM").

This station will operate with an antenna height above average terrain (normally abbreviated as "HAAT") of 30 meters (98.4 feet). For all intents and purposes, one can say that a LP 100 will operate with an ERP (effective radiated power) of 100 watts and a HAAT of 30 meters.

If you have a tower site in mind, or a building, or some other place to put your antenna, remember that if you exceed the height limit of 30 meters, then your output power (ERP) must be reduced so that your predicted 1 mV/m (one millivolt per meter) contour does not exceed what would be produced with 100 watts (or 10 watts) and 30 meters HAAT. If you have the software to do this, then the calculations aren't difficult. If not, there are now, and most likely will be many firms offering engineering services so you can prepare your application in plenty of time before the first LPFM filing window opens up. Also, remember that under the current rules, at least 75% of your board members must reside within 10 miles of the proposed station.

COVERAGE ISSUES

It's generally thought that using the normal 100 watt, 30 meter rules, your 1 mV/m contour will go about 3.5 miles from the antenna. This contour is considered good service, but in some cases it will be less, and in other cases it will go farther than you would think. Over the past 50 years it's been known that FM coverage generally exceeds predicted contours, and as FM receivers continue to improve, FM stations' coverage generally improves. And, keep in mind that if you provide a service people want to hear, and they go to lengths to get it, you could be heard many miles away-certainly further than what a coverage map would depict.

SAMPLE COVERAGE MAP

What you see here is a computer-generated FM coverage map showing the FCC's City-Grade (3.16 mV/m) and Service (1.0 mV/m) contours. We use a fictional site in Huntsville, Texas about 50 miles north of Houston. Please understand that this is for demonstration only, and in no way implies that any particular channel will fit at the site we've chosen for this demonstration.

As you can see, the 100 watt, 30 meter HAAT operation puts a "city grade" (70 dbu, or 3.16 mv/m) signal over all of the city limits of Huntsville, Texas. The service contour (60 dbu, 1.00 mv/m) signal extends beyond the city limits and would most likely provide good mobile coverage in the outskirts of the city.

 

With new rules in effect, it's more important than ever to get good advice, especially if you have no broadcast engineering background. There are a lot of reputable companies out there, and we'll be happy to recommend some to you-all you need do is ask. Some (like us) will do the engineering portion of the FCC Form 318, others will do the entire application. It just comes down to what you want done on your behalf. For a look at what we offer, go to the Services page on the website.