73.870

Part 73, Subpart G, Section 73.870 is a regulation in the Low Power FM (LPFM) radio service concerning the processing of LPFM applications.

Minor changes to authorized facilities

Overview

A minor change to a licensed facility can be filed at any time. While the rules for LPFM state that applications are processed in the order they are tendered (filed), the FCC's Audio Division has been following the practice that is used in other broadcast services where applications that are filed on the same day are considered as simultaneously filed and both cannot be processed. This departure from the rules has resulted in cases where the FCC has not acted on pending LPFM applications until one of the two parties withdraw their application.

Applications that do not meet the requirements for a minor change are considered major changes and can only be filed during a designated LPFM filing window.

Channel changes

Channel changes are sometimes done by LPFM stations as a result of a change made by a full-service FM or FM Translator facility that increases the amount of interference received by the LPFM station.

In order to change to a channel, regardless of the circumstances behind the channel change, the LPFM proposal must meet the required minimum distance separations of § 73.807 for other FM stations and for LPFM stations on 88.1~91.9, § 73.825 towards TV stations on Channel 6. Second adjacent channel waivers can be granted where appropriate. There are no exceptions that permits departure from the distance separation rules and acknowledged waiver types available under any circumstances. The Local Community Radio Act of 2010 prohibits the FCC from changing their rules to permit LPFM stations to be spaced closer to full-service FM stations than what is currently in § 73.807(a) and (b) of the Rules.

Changing to a "minor" channel

As a minor change, an LPFM station can change to a first-adjacent, second-adjacent or third-adjacent channel. They can also change to an intermediate frequency channel 53 or 54 channels (10.6 or 10.8 MHz) away. For example, an LPFM station on 104.5 can change to first-adjacent channels 104.3 and 104.7, second-adjacent channels 104.1 and 104.9, third-adjacent channels 103.9 and 105.1 as well as intermediate frequency channels 93.7 and 93.9 MHz. No additional justification is necessary to change to one of these "minor" channels.

Overview

In the case of interference either received by or caused by the LPFM station and none of the "minor" change channels are available or otherwise suitable, the LPFM station can change to any of the 100 FM channels (88.1~107.9). To change to a channel that does not meet the minor change requirements, a contour study must be conducted to demonstrate reduced interference. This means that an LPFM must compare the potential interference on the current channel with the potential interference on the proposed channel. This is different than the rule for FM translators which only requires a showing of interference on the current channel but no demonstration of improvement on the proposed channel.

Incoming interference

The most common form of LPFM interference is where a change by another facility increases the "noise floor" in a certain direction from the LPFM station. In some cases, this interference will cause an LPFM station to be completely obliterated in a significant part of their service area. When reviewing these cases, we look at the interfering contours of other stations on co-channel and the first-adjacent channels. We look at where the 40 dBu interfering contour (for co-channel interfering stations) or the 54 dBu interfering contour (for first-adjacent channel interfering stations) appear in respect to the LPFM station's 60 dBu service contour. We also look at the field strength of the interfering contour of those stations at the LPFM transmitter site. We do the same thing for the proposed channel. if, by looking at the 40 or 54 dBu interfering contours, we can show that on the new channel, there is more area of the 60 dBu LPFM service contour that is not overlapped by an interfering contour, then we have a showing that interference would be reduced. If interfering contours on both the current and proposed LPFM channel continue to overlap the LPFM 60 dBu interfering contour, we look at the field strength of the interfering contours at the LPFM site. If the field strength of those contours are weaker (a lower dB number), then we can make a showing of reduced interference.

Outgoing interference

Like with incoming interference, outgoing interference is caused by application activity by another facility. This would mean that the interfering contours of the LPFM station are overlapping the service contours of the other facility as set forth:

Other FM station class	LPFM interfering contour on co-channel	LPFM interfering contour on first-adjacent channel	Other station service contour	Other station "city grade" contour
Class B on 92.1~107.9	34 dBu	48 dBu	54 dBu	70 dBu
Class B1 on 92.1~107.9	37 dBu	51 dBu	57 dBu	70 dBu
Class B and B1 on 88.1~91.9 as well as all other FM service classes including FM Translators on any channel.	40 dBu	54 dBu	60 dBu	70 dBu

If the change results in a overlap of the appropriate LPFM interfering contour into the 70 dBu city grade contour of a full-service FM facility, the full-service FM facility can claim interference from the LPFM station and require the LPFM station to cease operations on the current channel. LPFM stations can use the same criteria to proactively request a channel change to any available channel under those circumstances. Unenforceable interference to an another station happens when the LPFM interfering contour overlaps the other station's service contour. These situations, when coupled with a showing that the proposed channel does not exhibit similar issues does carry a lot of weight with the FCC. Enforceable interference also takes place when the LPFM interfering contour overlaps the boundaries of the community of license of the other station. More information on enforceable interference can be found in § 73.809.

Station moves

A station wishing to move the location of their transmitting antenna must file that request with the FCC as a Minor Modification to Facility in LMS and a granted construction permit is required before any changes can be made. In addition, any changes in antenna height on the same tower either more than 2 meters (6 feet) higher or more than 4 meters (12 feet) lower will also require a granted construction permit.

As a minor change, an LPFM station can move up to 11.2 kilometers (6.96 miles) from their currently authorized site. LPFM stations that need to move further can make a technical showing by using a contour study that demonstrates that the 60 dBu service contour of the proposed location overlaps the 60 dBu service contour of the current LPFM facility, even if that overlap is minimal.

An LPFM station that is on a time share agreement may move more than 11.2 kilometers if the proposed site is the same as another LPFM station in the same time share agreement.