Encroachment in the LPFM service

revised March 11, 2008

NOTE: Due to the changes in §73.809 effective March 17, 2008, second adjacent channel interference is no longer considered legal interference where a full power station can displace an LPFM. Therefore, second adjacent channel activities will be listed as advisories and warnings and not necessarily as encroachments.

As a secondary service, LPFM operators are always concerned about changes made by full power broadcast interests which could either displace or cause significant degradation to the LPFM station.

This can be caused by full power stations:
# Increasing their class/power.
# Changing to a different location within their city of license.
# Change their community of license while moving and/or upgrading their facility.
# Petitioning the FCC to allot a new full power channel to a community.

To understand how interference is measured and some of the terms that we use here, please read our section on interference.

The REC LPFM Encroachment Report

Every week, REC provides a free service that warns LPFM stations of FCC application activity that can impact LPFM stations and applicants.

The LPFM Encroachment Report is available by clicking here.

The REC Encroachment Report covers most application activity by full power FM stations. Currently, the Encroachment Report does not cover:

# Assignments and transfers (since no facility change is done)
# Petitions to amend the Table of Allotments and other vacant allotment issues
# Canadian and Mexican activity
# TV Channel 6 activity

REC Encroachment Reports are usually issued on Saturdays and reflect FCC business from the past week.

Reading the Report

Most of the data on the report is very self explanatory. Here's a sample of a record on the report with line numbers inserted that are not seen in the actual report:

(2) Possible COL change from COTTONWOOD AZ
(4) Minor Modification of a Licensed Facilty - Accepted For Filing - 01/26/2007
(5) BPH-20070119AIF
(6) Channel 241C - Facility ID 51642
(7) Impacted LPFM stations:
(9) 242 PAYSON AZ - First Adj - 79.8 - RED

Here's an actual run-down of what each line means on the report:

* Line 1 indicates the full power station's call sign and community of license on the application.
* Line 2 only appears if the community of license on the application is different than the one on the facility record. Keep in mind, there may be another pending application that is actually requesting the community of license change but you can still use this data as a good trigger if you are tracking community of license changes.
* Line 3 is the name of licensee, permittee or applicant of the full power facility.
* Line 4 is the nature of the full power application, the current status of the application and the date of that action. The encroachment tracks all changes in status including the initial application, any amendments as well as the disposition (granted or dismissed).
* Line 5 is the FCC file number of the full power station's application.
* Line 6 is the channel number and class of the facility proposed on the application as well as the FCC facility ID number.
* Line 7 is a header to indicate that there is one or more LPFM stations encroached by the application.
* Lines 8 and 9 will appear for each impacted LPFM station. The data includes in Line 8, the call sign of the LPFM station involved, the LPFM facility ID, the LPFM station's channel number and the name of the LPFM licensee, permitee or applicant. Line 9 data includes the LPFM channel number, the LPFM community of license, indication of which adjacent channel the LPFM facility is at in respect to the proposed full power facility, the distance between the LPFM facility and the proposed full power facility in kilometers and an indication of the severity of the encroachment (see information below about REC encroachment levels).

Definitions of Encroachment

On the Encroachment Reports, REC defines each incident with a classification. These classification designations were created by REC to describe each encroachment on the co-channel, first adjacent channel or IF channels:


Yellow encroachment is displayed when the interference contour of the full power station overlaps with the LPFM's service contour. Yellow encroachment only displays on co-channel and higher powered first adjacent channel stations. Based on the full power station's location and the terrain between it and the LPFM, the LPFM may experience interference in the direction of the encroaching station.


Orange encroachment is displayed when the LPFM's interference overlaps into the buffer zone located 20 km beyond a full power station's protected contour. The FCC created the buffer zone to allow LPFM stations to stay on the air even if full power stations make short moves. While this operation may still be legal, the LPFM station may encounter more interference from the full power station resulting in a smaller coverage area. No new LPFM stations would be licensed in this area.


A red encroachment means that the full power FM station's primary service contour has overlapped the interference contour of the LPFM. LPFM stations with a red encroachment on the co-channel or first adjacent channel could suffer significant interference and may receive interference complaints from the full power station.


A MAJOR encroachment is displayed if the 60 dBu protected service contours of both the full power and LPFM stations overlap. This is considered interference per §73.809(a)(3). For IF channels (+/- 10.6 and 10.8 MHz), MAJOR will also be displayed if the 91dBu contours of the full power and the LPFM station overlap. LPFMs receiving a MAJOR message should start immediately considering remedial action or preparing a demonstration on how the LPFM will not cause interference to the proposed full power facility. MAJOR does not mean the end of your station, but it means you need to do some serious thinking about your next move.

City Grade

A City Grade encroacment is displayed if the 70 dBu City Grade contour of the full power FM station overlaps into the service contour of the LPFM station. This is legal interference under §73.809(a). LPFM stations should prepare for a possible complaint from the full power station and should start looking to make their next move.