LPFM is a single class of service. This class of service allows for a (60 dBu) service contour of 5.6 kilometers. This means that if you look at your overall service area, the average distance is 5.6 kilometers (3.5 miles) to the edge of the service contour (your actual distances will vary based on terrain but normally averages out to about 3.5 miles overall). 5.6 kilometers is based on 100 watts at 30 meters height above average terrain (HAAT).
Not all LPFM stations are 100 watts. If, based on height above average terrain, the station's antenna is higher than 30 meters, then the power must be reduced in order to keep the station's service contour within the average 5.6 kilometer service contour. This is why some LPFM stations are assigned with a lower power.
In 2015, REC Networks filed a Petition for Rulemaking, RM-11749, which among other things, called for an increase in the service contour from 5.6 kilometers to 7.1 kilometers. 7.1 km is the equivilent to 250 watts at 30 meters HAAT. Unfortunately, there is a lot of mis-information circulating that LP-250 is on the books and statations can upgrade. At this time, this is not the truth. Since the initial filing, docketing and collection of comments back in 2015, the FCC has not moved forward on "LP-250". Any discussion about a future 250 watt LPFM service is purely speculative.
Even without the power increase, some LPFM stations may be running less power than they are entitled to. This may be because of a problem with the FCC's application processing system or it may be possible to get a slight power increase using a different terrain database.
When an Form 318 application is filed with the FCC, the system calculates the HAAT based on the information given on the application. The FCC's system (which I refer to as "the overnight engineer") will sometimes get the calculations wrong and will short-change stations. If you look at your station in FCCdata.org, you will know that the overnight engineer assigned your power if (1) your HAAT has numerous digits to the right of the decimal point (34.244445 m) and/or the effective radiated power (ERP) is not rounded to the nearest watt (0.001 kW.. e.g. your ERP shows as something like 0.0453940). In this case, you may be short changed.
In addition, the FCC uses two different terrain databases for calculating HAAT. The legacy FCC 30-second database has been the long accepted source for HAAT in the continental United States. The second database is called GLOBE. GLOBE data was based on information collected from previous Space Shuttle missions to map the entire earth to determine elevations. HAAT readings using both FCC30 and GLOBE data can be obtained at the FCC's HAAT website. The FCC will accept either database, therefore you can use the one that provides the lower height in order to get you the most power.
The new version 2.0 of myLPFM, which was released in late 2017 has functionality that allows LPFM stations to simply enter their call sign and calculate their HAAT using both FCC30 and GLOBE data to determine if any kind of a slight power increase may be possible. If a power increase is possible, the station would need to file a Form 318 to request the FCC to correct the station's HAAT calculation and accordingly, to specify operation at the higher power. If the LPFM station is currently second-adjacent channel short-spaced, it would be expected that a new second-adjacent showing be made to demonstrate that the slightly upgraded facility would still not cause interference to listeners or potential listeners of the short-spaced second-adjcent channel station(s).
REC is able to do these power increases for you. Keep in mind, the power increase may only be slight and may or may not impact your overall coverage. Stations may want to look at other reasons for coverage related issues such as antenna height, location choice or antenna type (not all antennas are created equal). REC may be able to help.
- §73.811 LPFM Power and Antenna Height Requirements
- myLPFM Channel Search Tool from REC
- FCCdata.org - REC's broadcast facility lookup tool (view your station's HAAT and ERP)
- REC LP-250 Information
- FMpower - FCC tool that calculates ERP (power) based on HAAT. (Remember to select "100 watt LPFM" in the "station class" field.)
- Antenna Height Above Average Terrain Calculator - FCC tool that supports both FCC30 and GLOBE terrain data.