FMeXtra

Obsolete analog digital hybrid radio broadcasting technology
FMeXtra is a deprecated in band on channel digital radio broadcasting technology created by Digital Radio Express. It was intended to allow a second all digital signal to be simulcast with an existing analog FM radio station, offering a less noisy signal that would be particularly useful in urban environments where multipath distortion can seriously degrade analog FM transmissions. It can also support a second all digital channel at the same frequency, allowing two channels to be broadcast by a single FM station. FMeXtra was one of two competing systems considered by the FCC for standardization in the U. S., and by extension, Canada and Mexico. The other system, HD Radio, could carry up to four signals in a single channel and offer higher quality audio. FMeXtra's appeal was that it could be implemented at relatively low cost, requiring only a single rack mount case added to a radio station's existing equipment and transmitter plant. It required no license, unlike HD Radio which allows one free channel but requires 3% annual royalties for additional channels. After extensive consultation, the FCC chose HD Radio over FMeXtra. FMeXtra continued for a time before rebranding itself VuCast as a datacasting play, but that saw little adoption and Digital Radio Express eventually went out of business. References to the system generally end around 2013.

The system is run from a single rack unit box called the X1 Encoder, which is actually based upon a personal computer server and digital audio hardware from Lynx Studio Technologies (LST). Control is entirely via software, via gigabit Ethernet, USB, serial port, and SVGA video monitor. All processing is handled internally by a Pentium 4 running Windows XP. FMeXtra is fully compatible with HD Radio, which uses additional radio spectrum beyond the ±100 kHz signal. It is not compatible with all existing subcarriers. Thus, a radio station might have to remove its radio reading service for the blind, and replace it (and its dependent listeners' receivers) with a digital one. This would take up much less bandwidth, particularly since voice can be highly compressed. The signal is partitioned so that RBDS, stereo, or other existing subcarriers can be protected, at the expense of bandwidth. If used only for monophonic transmissions, no RDS protection exists for stations in Europe. The codecs used are AAC and aacPlus v1 and v2 and sample rates of 8 kHz (telephone quality) to 96 kHz (surround sound quality). The other codecs used are AMR WB+ that can create more multiple audio programs as well as limited multimedia can also be broadcast, as with HD Radio and DAB. The available broadcasting bandwidth for digital audio varies from 40 kbit/s while sharing the space with existing analog signals, or 156 kbit/s if all analog signals (except the base monophonic signal) are dropped. (For comparison, iBiquity's Hybrid Digital/analog system offers 100 150 kbit/s in shared mode, and 300 kbit/s in pure digital mode.) The coverage is similar to FM Stereo, and therefore high ERP is required in larger urban areas, as with normal FM transmissions. Digital Radio Express has since gone out of business, after a brief stretch where it rebranded itself as VuCast in an effort to emphasize the technology's datacasting capabilities.

FMeXtra is not in use anymore in the BeNeLux. Short test where running on the following stations:
93.9 Megastad, Rotterdam, The Netherlands, carrying Megastad Classics
96.5 Imagine FM, Brussels, Belgium, simulcast
98.4 Radio 538, Goes, The Netherlands, carrying Radio 10 Gold & JuizeFM
100.4 Q music, Rotterdam & Oude Polder, The Netherlands, carrying Radio Bem Bem
100.7 Q music, Lopik, The Netherlands, carrying Radio Bem Bem
101.2 Sky Radio, Hilversum, The Netherlands, carrying TMF Radio & Kink FM
101.9 Radio 538, Alphen, The Netherlands, carrying Radio 10 Gold & JuizeFM
102.1 Radio 538, Hilversum, The Netherlands, carrying Radio 10 Gold & JuizeFM
102.4 Radio 538, Terneuzen, The Netherlands, carrying Radio 10 Gold & JuizeFM
102.7 Radio 538, Rotterdam, The Netherlands, carrying Radio 10 Gold & JuizeFM
105.3 Delta Radio, Twente, The Netherlands, carrying Delta Piraat
106.1 Gold FM, Brussels, Belgium, simulcast + carrying Jet FM

89.1/Antenna 1: Heilbronn, Germany (soon on air)
103.4/Otto FM: Varese, Italy, carrying Chic FM
100.5/BBC WS: Riga, Latvia, Carrying Radio NORD and TOPradio