FCC101: "Honey, the new neighbors are moving in..."
News of a new or modified station on an LPFM's channel (or first-adjacent) can raise many concerns and "what ifs".
You may have seen the filing on FCC.today or was warned about it through the Encroachment Report at myLPFM. There is new application activity for either a new station or the modification of an existing station on your same channel or your first adjacent channel.
When new neighbors move in to a house or apartment next door, you are always concerned. Are they going to be noisy? Are they going to do illegal activities? How much will my quality of life be impacted? These same kinds of anxieties also exist when there is application activity in your area.
What can, or can’t be done, and in some cases, what will happen to your station will all depend on the type of broadcast station that is moving in.
The first important to thing to remember is that LPFMs are a secondary service. So are FM translators. Full-service FM stations, however, are primary services. This means the primary stations have priority over the secondary stations.
A quick primer on contours
The way that the FCC determines whether two stations will or will not interfere with each other is through field strength contours. There are two types of contours. Service contours (also known as protected contours) are used to establish a service area for the station. The area within the contour is predicted to receive the station at least 50% of the area and 50% of the time. The other type of contour is an interfering contour. Interfering contours are based on a prediction that the station will be received in 50% of the area and 10% of the time. While the service contour remains at the same level for all facilities (for LPFM, it is 60 dBu), the interfering contours will be based on channel relationship. For example, for LPFM, the interfering contour for co-channel is 40 dBu and for first-adjacent channel, it is 54 dBu. When using dBu, it is important to remember is that the higher the number, the smaller the area.
Service contour distances are based on a calculation of the station’s effective radiated power (ERP) and height above average terrain (HAAT). A complex mathematical formula, such as the one used by REC’s Curves Calculator is then used to determine the distance to the contour based on contour type (service or interfering), ERP, HAAT and desired (dBu) contour. In drawing a contour map, 360 of those calculations are made going in each direction and looking at a station’s ERP and HAAT in that specific direction. This is why some LPFM stations have unusually shaped service contours as opposed to a perfect circle (which can happen in areas with very flat terrain).
The general theory of contours is that if the service contour of the “desired” station and the interfering contour of the “undesired” station have overlap, then it is considered interference.
So, what can be done when the neighbor starts to unpack and move in on the dial?
First, make sure your own house is clean
In situations where the rules do allow an LPFM station (or any station for that matter) to request Commission action to address interference from a subsequently authorized station, you will be expected to certify that your station is operating within its authorized parameters. This means location, height, transmitter power output and effective radiated power are the same as what is on your current license authorization. Make sure the antenna listed in your last license to cover application is the same one you are still using. If not, these changes will need to be made.
Remember, any changes in your operating parameters depending such as location, height changes (over a certain length) and channel must be authorized by the FCC first through a construction permit. Changes of antenna and feedline (with no other changes) can be done without advance authorization but the FCC must be notified through a modification of license application. Contact REC for assistance.
REC does offer the Self Inspection Checklist where you can do your own checklist for compliance. It’s better to find problems on your own right now than be discovered later by a FCC field inspection.
Now, we can look at your neighbor
As I mentioned, the way interference or potential interference will be handled is based on what type of neighbor you get.
LPFM
The FCC’s approach to LPFM is simply, just keep everything simple. LPFM uses simple minimum distance separation requirements to other LPFM stations. 24 kilometers (14.9 miles) for stations on the same channel and 14 km (8.7 miles) if on a first-adjacent channel (for example, 95.3 or 95.7 if your station is on 95.5). Actual contours, which we said can vary in size based on terrain and other factors play absolutely no role. The FCC is very clear on this. As long as the new or modified LPFM station meet the §73.807 distance separation requirements, it is not considered interference regardless of the contours in respect to LPFM1, full-service2 as well as FM translator and booster stations.
FM translator stations
FM translators protect LPFM stations, full-service and other FM translators using the contour method. This means that the appropriate interfering contour of the proposed translator facility cannot overlap the service contour of the existing station. FM translators are only required to protect LPFM stations on co-channel and first-adjacent channels. Since FM translators can be directional, the interfering contour can be engineered to prevent the interfering contour from overlapping a service contour. This can mean that the addition of a FM translator facility could result in a “short spacing” under the LPFM distance separation rules.
The LPFM distance separation rules in §73.807 considers each FM translator as being nondirectional with a service contour size (as calculated) to be either 7.3, 13.3 or 20 kilometers, even if the directional antenna is “looking away” from the LPFM station.
FM translators do have a remediation policy if a subsequently proposed translator causes predicted interference3 or if the subsequent translator causes actual interference.4 The translator interference policy not only considers listeners within the service contour of the existing station (60 dBu for LPFM), but extends out to protect listeners within the wider 45 dBu service contour area. There is a specific formula that is used to determine if a listener is experiencing interference and there is a threshold on the number of valid listener complaints using that formula to determine if the interference is actionable.
We have more information about this process at the REC website. While this document was written for LPFM stations, it does also apply to when the incumbent station is a full-service or another FM translator.
FM booster stations
FM booster stations are intended to fill in coverage gaps of full-service and LPFM stations. They operate on the same channel as their host station and must be engineered in a way where the service contour of the booster must remain entirely within the service contour of the host station.
FM boosters protect other stations using contours but only on first-adjacent channels. LPFM and FM translator stations do not have any specific protection requirement towards FM booster stations. This is because those stations are required to protect the host station which has a larger service contour on the same channel.
With the FCC recently allowing FM booster stations to be able to originate up to 3 minutes per hour of programming different than their host station5, there has been an uptick of new FM boosters being added. Also, unlike other broadcast stations, FM booster stations can be proposed at any time without needing to wait for a filing window.
Under the current rules, existing LPFM, full-service and FM translator stations can use the same rules that apply to FM translators but for actual interference only. The predicted interference rules in §74.1204(f) do not apply to subsequently proposed FM boosters. This is something that REC is seeking to change through a rulemaking proceeding.
Therefore for now, if a new or modified booster is authorized, you will have to wait until it is on the air before any action can be taken.
Full-service FM stations
Full-service stations, both in the reserved band (88.1~91.9) and in the non-reserved band (92.1~107.9, sometimes referred to as the “commercial band”) are only required to protect other full-service FM stations. In the reserved band, this is done through contours.6 For the non-reserved band, this is done through distance separation pursuant to §73.207 or through a hybrid of distance separation and contours, pursuant to §73.215 of the rules. As a primary service, full-service FM facilities are not required to provide any protection to secondary services such as LPFM, FM translator and FM booster stations.
Likewise, there is no avenue for an LPFM station to complain about the arrival of a subsequently authorized full-service station. This includes increased “noise” or a “hijack” effect as a result of a co-channel or first-adjacent channel station adding or improving HD radio.
The arrival of a new full-service FM station on the same or adjacent channel will have the reverse effect on LPFM stations. Since the full-service FM station can ignore the existence of LPFM stations when determining where to go, it is very possible that a new or modified full-service FM station can not only cause substantial interference, but can be in a position to demand that an LPFM station ceases any operations that interfere.
While the presence of a new full-service station can create anything from a new level of noise-floor to shattering interference, there are specific rules that apply to full-service stations in order to demand an LPFM to go off the air until the interference can be resolved.
The interference remediation policy for subsequent full-service stations into an existing LPFM area can be found in §73.809 of the rules. These policies only apply to LPFM stations that are on the same channel or the first-adjacent channel of the subsequent full-service FM station and apply only where there is overlap between the LPFM station’s interfering contour and any of the following:
The full-service FM station’s 70 dBu contour (also known as the community coverage or “city grade” contour).
The legal boundary of the community of license for the full-service FM station, or
Any area within the legal boundary of the community of license of the full-service FM station that is predicted to receive at least a 60 dBu signal (this definition is pretty much redundant with the previous bullet point).
When there is such overlap, the FCC will not automatically shut down the LPFM station. A request must be filed by the full-service FM station to start the process.
LPFM stations changing channels to get out of the way
Upon a technical showing of reduced interference (either incoming or outgoing), an LPFM station may change to any of the 100 channels as long as all §73.807 and §73.825 requirements are met.7 Channel changes to what is considered an “adjacent” channels, as long as §73.807 and §73.825 requirements are met, does not require a showing of reduced interference.8
Contacting the other station
I understand that there may be an urge to contact the other station and give them a your piece of mind for “invading” “your” territory. Unfortunately, I have heard about folks doing this and I do not condone it in any manner. This is bullying.
It is appropriate and also required before making a complaint against a FM translator or FM booster station under §74.1203 or §74.1204(f) that you need to reach out to the station to try to privately resolve the interference complaint before submitting it to the FCC. For the sake of the service and for your own sake, please keep those contacts professional, even though your blood may be boiling inside. The FCC expects stations to try to resolve the issue first before dragging in the agency. We have seen our share of cases where that phone call or letter resolved an issue and made the translator operator try something different.
Never contact a modified a new or full-service station unless it is to let them know what your game plan is for moving off of their channel.
What if the other station is “riding dirty”?
Bad apples exist. All services have them, even LPFM. However, sometimes they are hard to catch. As I mentioned earlier, before going out and complaining about another station, make sure your ship is in order. You know, glass houses and all.
If you have solid evidence that another station is operating from an unauthorized location, operating at the wrong height, excessive power, etc., then you can either file an informal objection against any subsequent license to cover application for the offending facility or if the license application is already granted, then you need to go through the FCC complaint process.
Remember, you must have rock solid, iron clad evidence of wrongdoing. The Commission will not accept hearsay. Posts from social media and message boards are considered as hearsay. You need your ducks in a row. There’s no guarantee to how fast the FCC will do something about it, if they do something. Also remember, the FCC field enforcement organization is thinly staffed and has limited resources. Priority is given to safety of life and the telecommunications infrastructure. Radio is not at the top of the list when there’s other places the field needs to be.
Follow the same complaint process if the “dirty” station is a pirate (operating without FCC authorization). I have found that pirates are low on the list unless you are in New York City or Miami.
Out of town neighbors
Radio frequency is a natural resource and can be impacted by certain atmospheric phenomena. Therefore, there may be times when you may experience a station from a fairly long distance away start to come into your area and cut into your service area. Later in the day they may be gone. There are some scientific explanations for these things happening and is a bit out of scope for this.
Again, if you notice that another station, mainly full-power FM is starting to be heard and you don’t see any application activity for that facility, don’t panic. Don’t automatically assume that they “turned up the juice”. Whatever you do, do not call the station and complain about it (I have seen people do this and it did not go over real well).
All FM services are subject to effects such as tropospheric ducting and “E-skip”. It may come and go throughout the day and throughout the year. June and December are two of the most intense months for this to happen.
In conclusion
The radio spectrum is finite and the demand exceeds the supply. The FCC does have regulations that determine the placement of broadcast stations. Many are based on old fashioned methods but also take into consideration certain aspects mandated by Congress, such as the fair distribution of licenses across the many states and communities.9
If your station is an LPFM and if you are already licensed or if a new 2023 LPFM, at least two days after your license to cover application is granted, please sign up for myLPFM.com. This is a free service for all LPFM stations that may help troubleshoot and look out for interference.
Please set the example for other stations, especially new entrant broadcasters by being a good spectrum neighbor. It is for the betterment of the LPFM service and is one more step and making sure that radio remains relevant.
See Calvary Chapel of Redlands dba Packinghouse Christian Fellowship, Letter, 31 FCC Rcd. 12694 (MB, 2016).
See Amendment of Section 74.1231(i) of the Commission’s Rules on FM Broadcast Booster Stations, Report and Order, FCC 24-35, 89 FR 26847 (2024).
For example, if the LPFM station is on 92.5, the adjacent channels include: (1) co-channel (92.5), (2) first-adjacent channels (92.3 & 92.7), second-adjacent channels (92.1 & 92.9), third-adjacent channels (91.9 & 93.1) and intermediate frequency channels, +/- 53 and 54 channels or 10.6 or 10.8 MHz which for an LPFM station on 92.5 would include 103.1 and 103.3).