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FCC Low Power FM Application, Technical Sections

How do you fill out the technical portions of a new low-power FM (LPFM) application? Read on!

You’ll need some detailed technical information, some information about the proposed antenna site, and if you don’t own the site, the name and phone number of someone who can vouch for your reasonable assurance agreement to use that site in the future. If you’re not working with an application engineer, you can get technical information from the FCC LPFM channel finder or Prometheus RFree, which is more thorough. We recommend using an engineer with experience filing with the FCC and you can hire Prometheus engineers by contacting us here.

This guide will only cover the technical sections:


“Facility ID” is automatically assigned by the FCC, and is a 6-digit number to identify your station, even before it has call letters, and even if the call letters change.

“City” for LPFM stations is informal compared to full-service FM stations, so you can use locations like “West Philadelphia”, which is a well-known region of Philadelphia.

“Channel” 201 means 88.1 MHz and 299 is 107.9 MHz. The “Frequency” box will show the corresponding frequency, so you can be sure to choose the right one.

If you are completing the application yourself and have not hired an engineer for this section, DO NOT pick a frequency without extensive research using Prometheus RFree or another commercial FM allocations software. Most metropolitan areas in the US have a crowed FM dial and your application like won’t be successful without significant detailed engineering work by a professional. Contacting us for support.



FAA registration is required for some antenna structures, including all structures at least 200 feet tall. How do you know if FAA registration is required for a shorter structure? Ask your web browser to find FCC TOWAIR and follow the instructions on that form. You’ll need to know the structure’s latitude and longitude, (proposed) height and structure type (tree, building, tower etc). You’ll also put that same data on this form so that the FCC can double check whether the structure needs registration. If you’re confused about coordinates, our guide to getting coordinated can help.


If you’re asking to put your antenna on an existing registered structure, answer “yes” and fill in the ASR number (ASRN). You’ll get that number from the structure owner/agent and/or your application engineer.

If your proposed structure requires registration, or if the existing structure requires registration and isn’t registered yet, you’ll have to begin the FAA process (which is beyond the scope of this guide) and select “Filed with the FAA”.

If your structure doesn’t require registration, answer “No”.




What is your proposed antenna’s latitude and longitude? How about the ground elevation? You can find help in our guide to getting coordinated.

It is a serious problem if your antenna is not at the location approved by the FCC.

“Support Structure” is a tree, tower, pole etc but does not include antennas attached to it. “Overall” height is the tallest bit of anything, whether it’s the support structure, your antenna, another antenna, lightning rod or whatever.

The FCC uses the metric system, and so must you! There are a lot of online converters but here’s the formula: meters = feet / 0.3048

When you’re using an FAA-registered structure, the coordinates, type, heights, and ground elevation are in the federal registration, and normally they should match what you enter on this form. However at times the registered values are pretty far off, in which case you might enter accurate values here, and attach an explanation to your application.


How high are you proposing to mount your antenna (meters again, not feet)? If your antenna is 2 meters tall, its radiation center is often taken to be 1 meter from the bottom (or top).

We usually insert the height into both boxes. The FCC calculates the grey boxes when you press “Calculate ERP”, and historically that calculation is sometimes incorrect. Don’t worry about it for a new-LPFM application.





Most LPFM antennas are non-directional (omnidirectional). Directional LPFM antennas reduce coverage(!) [despite what some people say] and so are used only specialized situations, where you or your application engineer really to know what they’re doing!





That’s it for your antenna’s technical information… for now at least! The remainder of the technical sections deal with whether your proposed antenna location meets FCC requirements. Some of these are complicated and you should consult the FCC instructions for this form and perhaps the LPFM Regulations.


It’s best to read the FCC instructions starting on page 14 because this can get complicated. Besides protecting wildlife, wilderness and wetlands; this also refers to protecting historical and sacred sites; including from high-intensity lighting; and protecting people from harmful levels of radio energy. The missing Environmental and RF Safety worksheets can be found in the old form 318 instructions on pages 16 and 17.




Is your proposed station far enough away from other FM and TV stations according to the FCC rules? Some situations are simply “yes” but some aren’t. You’ll typically get this information from an application engineer or an online “channel finder”. It is not unusual to upload a fairly-detailed exhibit, even when selecting “yes”.

You may be allowed to be “too close” (short spaced) to TV6 stations, and also to other FM stations which are two channels away from (second adjacent to) your proposed channel, under certain conditions. “Certain conditions” may also apply for locations near the border with Mexico or Canada, and not all of that information is in the regulations. You might need an application engineer.

A common misunderstanding is that Reasonable Assurance requires locking in all the details as if you were ready to sign a tower-rental lease, like the exact height, antenna model, coax length, electrical and internet hookups, cabinets or rack mounting, concrete pads, ice dams, rental fees etc etc. That’s premature since the FCC has yet to grant your application, which might take years or not happen at all.

Instead, reasonable assurance means that you have a workable plan to build what you propose, at the site you propose, including reasonable-assurance agreements with owners/agents of sites you don’t own. You also should be reasonably assured that local authorities — zoning boards, homeowners associations etc — won’t block your antenna-building proposal because competitors can use that against you!

Tower-rental companies often have reasonable-assurance agreement templates already, but they are pretty simple. The agreement can even be a simple email. You do not need to attach the agreement to your FCC application — the most-important thing is that someone can verify the agreement with the owner or their representative using the name and telephone number you supply. Examples:

American Castle Towers will negotiate in good faith for Old-Tyme Radio to mount an FM transmission antenna on our tower located at 1600 Pennsylvania Ave, subject to their FCC authorization. Our agent Homer Simpson at 202-555-1212 can confirm this agreement.

Old-Tyme Radio has permission to build an antenna structure in the back yard of my property at 127 Kings Hwy if they get FCC approval to do so. -Dr Horton Who, 202-555-1212

See our Reasonable Site Assurance guide with templates.

Congratulations on finishing the technical portions of your new-LPFM application! Consider hiring Prometheus to review your application before you file.