HD Radio for LPFM

LPFM stations are permitted to install and operate HD Radio.  HD Radio permits stations to broadcast in digital quality, add up to 3 “sub channels” for different programming as well as send album art and titles to compatible receivers.  This is in addition to continuing to provide an analog signal receivable on all FM radios.

Facility considerations

In order to set up HD Radio, you will need to make sure that your studio/audio chain can handle the additional subchannels if you deploy them.  If you do run subchannels, you must make sure that your EAS can interrupt all of the subchannels during alerts. 

Because of transmitter power limitations in the GatesAir FAX150 certified transmitter, you may want to make sure that you are running an antenna that does not exhibit loss.  For example, a one bay circular polarized antenna like the Nicom BKG-77 or Shively 6812B may experience over 3 dB of loss.  For an HD operation, you should make sure that you have at least a 2 bay circularly polarized antenna.  For the Nicom BKG-77, space the two bays at 0.85 wave ((300 / frequency MHz) x 0.85 = meters) for best gain opportunities.  LPFM stations not contending with a second adjacent waiver can use a gain vertical antenna like the Norwalk Dominator.


There are currently two companies making transmission equipment for HD Radio, Nautel and GatesAir.  


As of March 1, 2021, the VS-300LP equipped with the VS-HD is now FCC certified. 


The Flexiva series transmitters are FCC certified and can be adapted to HD.  HD is achieved by adding an additional board inside of the transmitter.  You will also need an importer/exporter, the Flexiva FMXi 4g in order to bring in your multicast programming.  


The actual maximum power of the digital carrier is based on a percentage of the authorized ERP for your LPFM station.  That percentage is based on whether protection to a first-adjacent channel facility is required.  To determine this, we do a contour study based on an interfering contour of the LPFM station and the service contour of the other station.  Taking the nearby first-adjacent channels into consideration, this is the chart for how much power an LPFM can run based on the class maximum of 100 watts ERP.  If your station’s ERP is lower due to height above average terrain, these numbers will have to be adjusted:

Interfering F(50,10) contour of the LPFM that reaches the 60 dBu contour of the other first-adjacent channel station

Operation allowed at x decibels below carrier (dBc)

Digital can be % of analog power

Digital power for maximum class (100w) LPFM station

51.2 dBu or above

-14 dBc


4 watts

50.7 dBu~51.1 dBu

-13 dBc


5 watts

50.3 dBu~50.6 dBu

-12 dBc


6 watts

49.6 dBu~50.2 dBu

-11 dBc


8 watts

Less than 49.6 dBu

-10 dBc


10 watts

NOTE: Class B and B1 stations in the commercial band, despite having larger service contours, will still be “protected” at the 60 dBu contour. 

Don’t let these low powers fool you, a digital signal does travel a little differently than an analog signal.  Even at the maximum -10 dBc, the digital signal may not replicate your full analog service area, but it will perform better than 10 watts analog.  LPFM stations operating with foothill effect conditions (higher elevation/lower HAAT) will probably fare the best, but may also be prone to more first-adjacent channel issues.

The 2010 Order in MB Docket 99-325 outlines the policies related to the remediation of interference from a station operating HD to the analog signal of a first-adjacent channel station of any class.


When broadcasting in HD, your station is sending a digital bitstream.  That bitstream can be divided up among your multicast channels.  The bandwidth can be configured where you have better audio quality on HD1 and HD2 with a lower quality on HD3 and HD4.  The fewer multicast channels the station has, the better the quality can be distributed among those channels.

Your HD1 channel MUST match the programming on the analog channel.

LPFM and NCE stations must keep ALL multicast channels noncommercial in nature.  The rumors you may have heard that LPFM/NCE stations can run commercials on HD2 are not true.

HD multicast channels must be identified at the top of the hour like the analog channel.  IDs on the digital channels (including HD1) need to not just include the call letters (including the -LP for LPFM) and the city, but also some kind of an acknowledgement of the digital service.   Some legal ID examples include:

  • WREC-LP HD1 Riverton
  • WREC-LP and WREC-LP-HD1 Riverton
  • WREC-LP Digital HD1 Riverton
  • WREC-LP 102.7 HD1 Riverton
  • WREC-LP HD2 Riverton

All multicast channels must be connected to EAS in the audio chain and must forward alerts pursuant to the FCC rules regarding national alerts and in accordance to the state EAS plan.

Costs to convert

HD is not cheap.  For the equipment, budget at least $30K for the HD equipment and ancillary devices.  Also, as we mentioned, you may need to rethink your antenna due to the transmitter power output limitations on combined FM/HD transmitters.

For noncommercial radio (full-service and LPFM), Xperi (formerly iBiquity) charges a one time licensing fee of $5,000.  This license fee can be paid at $2,000 up front and then $500 annually until paid off.  Noncommercial stations do not have to pay any additional fees based on revenues and the noncommercial license covers all multicast streams.  You must have a license with Xperi before you can take delivery of HD equipment.

FCC filings required

An LPFM station can turn on HD without advance permission from the FCC.  Once HD has been activated, the station is required to file a Digital Notification with the FCC.  This form is available through LMS.

FCC decisions

MB Docket 99-325: Report and Order 17 FCC Rcd. 19990. (Declares that in-band, on channel to be the sole digital technology permitted on FM/AM broadcast stations. Permits interim IBOC operations)

MB Docket 99-325: Multicast Operations 20 FCC Rcd. 5136. (Permits experimental multicast operations.)

MB Docket 99-325: Second Report and Order 22 FCC Rcd. 10344 (Permits regular use of IBOC digital broadcasting, LPFM specifically permitted at paragraphis 56-58, establishes technical rules.)

MB Docket 99-325: Third Order 25 FCC Rcd. 1182 (Permits power increases for digital sidebands with first-adjacent protections as described above).

More information

Please review the websites of the various stakeholders:

REC can help with your Digital Notification and to determine if the LPFM station can operate at increased digital power.  LPFM licensees can get more information on HD digital power for their station through the myLPFM.com portal.

LPFM stations operating HD Radio

(As of February 21, 2024)

  • KXRN-LP Laguna Beach, CA
  • KBUU-LP Malibu, CA
  • KVCB-LP Vacaville, CA
  • WMXR-LP Miami, FL
  • WGVV-LP Rock Island, IL
  • WZRF-LP Wilmington, NC
  • KMGG-LP Albuquerque, NM