REC's "Plan B" for LPFM allocations

REC's "Plan B" is an alternate concept compared to the simplified process for a 250-watt LPFM service as proposed in REC's RM-11749 petition for rulemaking.  While REC had been working on "Plan B" for the past few years, a concept similar to Plan B was brought up by LPFM.AG in their petition for rulemaking, RM-11753.   LPFM.AG supports a complete replacement of the distance separation requirements for LPFM stations in §73.807(a) of the rules with "translator rules" or a complete contour overlap model.  

While REC supports a complete replacement of distance separation with contour overlap for LPFM stations (maintaining a maximum service contour of 7.3 km), the FCC is prohibtied by statute from removing the distance separation element of LPFM.  This is due to Section 3(b)(1) which says that the FCC shall not amend its rules to reduce the minimum co-channel and first- and second-adjacent channel distance separation requirements in effect on the date of enactment of this Act between low-power FM stations and full-service FM stations. 

But perhaps there's a way that it can be done.

Notice the phrase that was underlined, "in effect on the date of the enactment of this Act".  At the time the LCRA was enacted, there were two distance sepation tables in §73.807 of the rules, one for LP-100 and the other for LP-10.  It wasn't until the Sixth Report and Order in November, 2012 that LP-10 was removed from the rules.  Therefore, at the time of the enactment of the LCRA, LP-10 was still on the books. 

Also, notice that the same statute also states that minimum distance separation is required only between "low-power FM stations and full-service FM stations".  Section 3(a) of the LCRA makes a specific distinction between "full-service" FM stations, FM translators and FM booster stations.  With that, an argument can be made that the requirements of Section 3(b)(1) do not apply to translators and boosters and that the FCC can change protection by LPFM stations from distance to contours without any statutory restrictions.

Plan B - the best of both

Plan B is a method of providing flexiblity in the LPFM service by giving LPFM stations more freedom to engineer their stations out of a single cookie-cutter model in a manner that meets the statutory requirements of the Local Community Radio Act.   Plan B proposes:

  • A two-step process for protecting domestic full-service FM stations by first applying the minimum LP-10 distance separation requirement and then overlapping that with a contour overlap requirement.
  • A one-step process for protecting FM translator, FM boosters and other LPFM stations by using strictly a contour overlap method. 
  • The option for LPFM applicants to follow the FM translator protection methods in respect to foreign FM stations. 
  • The replacement of the minimum distance separations to TV Channel 6 stations in the LPFM rules by the contour overlap method in the translator rules. 

Plan B also calls for a maximum service contour of 7.3 km (250 watts at 32m HAAT) in all areas except within 125 km of Mexico where stations are limited to 50 watts ERP.   To make LPFM as flexible as possible, REC is asking for the ability for LPFM stations to utilize directional antennas for the purpose of protecting other station's service contours. Operating a directional antenna would not reduce the minimum LCRA distances between to stations and LPFM stations are advised that directional antenna grants do not carry any automatic program test authority as proofs of performance are required prior to a license application being granted. 

How to qualify a channel for Plan B


First of all,  all domestic full-service stations must be the following distances away from the LPFM station:

Full Service Station Class Co-channel minimum separation First adjacent channel minimum separation Second adjacent channel minimum separation
A 59 (PR/VI: 72) 53 (PR/VI: 66) 29 (PR/VI: 42)
C3 69 64 39
B1 77 (PR/VI: 84) 70 (PR/VI: 78) 45 (PR/VI: 53)
C2 82 77 52
B 99 (PR/VI: 126) 91 (PR/VI: 118) 66 (PR/VI: 92)
C1 103 97 73
C0 114 108 84
C 122 116 92

Second adjacent channel minimum separations can be waived upon a showing of a lack of interference to populated areas. Full service stations on third-adjacent channels carrying a radio reading service will also be protected at the second adjacent channel levels.

If the LPFM station is proposed to operate between 101 and 250 watts, LPFM stations must also protect the intermediate frequency (+/- 53 and 54 channels or +/- 10.6 and 10.8 MHz) as follows:

Full Service Station Class Intermediate Frequency minimum separation required
A 6 (PR/VI: 10)
C3 9
B1 9 (PR/VI: 12)
C2 12
B 12 (PR/VI: 22)
C1 20
C0 22
C 28

PR/VI: indicates the minimum separations for stations in Puerto Rico and the Virgin Islands.


The interference contour of the proposed LPFM station can not overlap the service contour of another domestic FM broadcast facility as shown:

Commercial Class-B stations on 92.1 through 107.9:

Frequency Separation Interference contour of proposed LPFM station Service contour of existing station
Co-channel 0.05 mV/m (34 dBu) 0.5 mV/m (54 dBu)
First-adjacent 0.25 mV/m (48 dBu) 0.5 mV/m (54 dBu)
Second-adjacent* 50.0 mV/m (94 dBu) 0.5 mV/m (54 dBu)

Commercial Class-B1 stations on 92.1 through 107.9:

Frequency Separation Interference contour of proposed LPFM station Service contour of existing station
Co-channel 0.07 mV/m (37 dBu) 0.7 mV/m (57 dBu)
First-adjacent 0.35 mV/m (51 dBu) 0.7 mV/m (57 dBu)
Second-adjacent* 70.0 mV/m (97 dBu) 0.7 mV/m (57 dBu)

Class A, C3, C2, C1, C0 and C stations on any channel, Class B and B1 stations on 88.1 through 91.9 and Class-D (secondary) non-commercial educational stations:

Frequency Separation Interference contour of proposed LPFM station Service contour of existing station
Co-channel 0.01 mV/m (40 dBu) 1 mV/m (60 dBu)
First-adjacent 0.05 mV/m (54 dBu) 1 mV/m (60 dBu)
Second-adjacent* 100.0 mV/m (100 dBu)  1 mV/m (60 dBu)

Low Power FM stations, FM translators and FM booster stations:

Frequency Separation Interference contour of proposed LPFM station Service contour of existing station
Co-channel 0.01 mV/m (40 dBu) 1 mV/m (60 dBu)
First-adjacent 0.05 mV/m (54 dBu) 1 mV/m (60 dBu)
Second-adjacent None required None required

* - Second adjacent channel can be waived based on a showing of no interference in populated areas to the short spaced station.  Full service stations on third-adjacent channels carrying a radio reading service will also be protected at the second adjacent channel levels.

Maximum Power with Plan B (translator rules)

If LPFM was to follow the non fill-in FM translator rules, then the rule for maximum effective radiated power (MERP) as shown in §74.1235(b) would apply.  Here's a comparison of how the maximum power for a station is determined for each service:

LPFM Rules FM Translator Rules
The overall height above average terrain (HAAT) is calculated by calculating the height above average terrain along 8 different radials spaced at 45 degrees from true north and then they are added and averaged.  If the HAAT is 30 meters or less, then the maximum power is allowed (100 watts for LP-100 or 250 watts at LP-250).  If the HAAT is over 30 meters, then a calculation is done to determine the amount of power necessary to produce a 60 dBu service contour of 5.6 kilometers (7.1 for LP-250).   The height HAAT is caculated along 12 radials spaced at 30 degrees from true north.  From each radial, a "maximum ERP" (MERP) for each of the12 radials is determined by cross referencing the HAAT with a chart showing the MERP for that HAAT.  If the translator is operating a non-directional antenna, then the station must use the lowest of the 12 MERPs that were determined.  

So, this means that under the translator rules, we would look at the height above average terrain in 12 different directions.  For each of those results, we would assign an effective radiated power using this chart:

Radial HAAT (meters) Maximum ERP (MERP in watts)
Less than or equal to 32 250 watts
33 to 39 170 watts
40 to 47 120 watts
48 to 57 80 watts
58 to 68 55 watts
69 to 82 38 watts
83 to 96 27 watts
97 to 115 19 watts
116 to 140 13 watts
Greater than or equal to 141 10 watts

For the purposes of Plan B, we are only using the "East of the Mississippi" chart (§73.1235(b)(1)) in order to preserve the hyperlocal nature of the LPFM service by maintaining a service contour of 7.3 kilometers.

Under Plan B, LPFM stations that are located in foothill locations would not be able to take advantage of their low overall HAAT in order to operate at a full 100 or 250 watts and place a service contour that has a substantally long lobe in one direction.   

For example, let's say you want to propose an LPFM station in the foothills of the San Fernando Valley in Los Angeles.  Under the current LPFM rules, your location is at -49 meters HAAT and you would be granted the full power allowed however, under Plan B (the translator rules), your power would be substantially reduced:

Radial 0 30 60 90 120 150 180 210 240 270 300 330
HAAT -216 -182 -113 57 116 128 70 79 -60 5 -199 -274
Maximum ERP 250w 250w 80w 13w 13w 38w 38w 250w 250w 250w 250w 250w

In this case, since the lowest Maximum ERP is 13 watts, the LPFM station running under Plan B would be limited to 13 watts ERP which would still give the station a 7.3 km service contour in the direction of population. 

Using myLPFM to do Plan B studies

REC has set up a system to allow the general public to run channel studies using Plan B.  To perform Plan B studies, do the following:

  • Go to and enter the location you want to evaluate like you normally would for an LP-100 station today.
  • Click on the [Site Details] button and enter the details about your tower. 
  • Click on the [Search for Plan B] button on the left side, a separate browser window will open up.
  • A new window will appear that will show the service contour at 10 watts.  
  • The left side will also show potential channels at 10 watts that both pass the LCRA minimums and based on point-to-point measurement along the radial between the LPFM and the other stations, does not have any estimated contour overlap.  
  • In the section "Overlap Study Editor", you will see a channel pull down bar.  This bar includes all channels that meet LCRA minimums for co-channel and first-adjacent channel, channels that are shaded may not be available due to contour overlap, but you can try them.  
  • Next to the Channel is another pull down bar for Proposed ERP.  This will include all available ERP levels that this location would be authorized for. 
  • Click on the "Co & First Adjacent" button to generate a contour study for the channel and ERP selected.  You will see as many as 7 curves surrounding the proposed LPFM site.  The black one closest to the LPFM station is your service contour, the rest are interference contours.  The grey circles with the shading are the LCRA minimums.  In order to have a lack of contour overlap, the thin interference contour line around the LPFM site must not overlap the thicker service contour line of the same color of the other station.  So remember, red with red, blue with blue, etc. 
  • Other buttons will generate other contour reports including the information on second adjacent channel waivers. 
  • The "TV6 Study" button will only work on channels 201 through 220 (88.1 to 91.9) to determine if there is no interference to TV Channel 6 stations.

Potentially Asked Questions (PAQ)

How would Plan B be better for LPFM?

Plan B can help some LPFM stations be able to stretch their coverage and perhaps use a directional antenna to stretch it out in one direction even farther.  Plan B can bring LPFM stations into tight spectrum areas that a regular LP-100 station could not fit.  For some areas, like the foothills, it will make a more hyperlocal LPFM service while still making room for more urban co-channel LPFM stations. 

What are the "cons" of Plan B?

Plan B would restrict power, especially for those in foothill locations and therefore may not handle well for those inside the interference contour of a full power station.  Plan B is not a "do it yourself" service, it will require engineering similar to that used for FM translators.   

If there are cons with Plan B, why is REC endorsing it?

We are not necessarily endorsing it, we are putting it on the table as an option.  When REC filed our Petition for Rulemaking RM-11749, we had both Plan A (distance separation) and Plan B (contour overlap limited by distance separation) on the table.  We decided to go with Plan A as it would require the least amount of changes.

We do note that on a wider scale, Plan B is friendlier to full-power broadcasters as it would limit LPFM service contours to the edges of full power and translator service contours where with today's LPFM, there is a possibility of contour overlap.  

We have introduced Plan B also to demonstrate that even with the LCRA in place, it is still possible to remove the distance separation tables between LPFM stations and translators and other LPFM stations without violating the statute.  Even if Plan A was introduced, we would still like to see the Plan B protection to other LPFMs and translators move forward.  

We are putting the information out there and we will let you be the judge.