FMeXtra

FMeXtrais a deprecatedin-band on-channel digital radio broadcastingtechnology created byDigital Radio Express.It was intended to allow a second all-digital signal to besimulcastwith an existing analogFM radio station,offering a less noisy signal that would be particularly useful in urban environments wheremultipath distortioncan 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 theFCCfor standardization in the U.S., and by extension,CanadaandMexico.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 singlerack mountcase added to aradio station's existing equipment andtransmitter 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 itselfVuCastas adatacastingplay, but that saw little adoption and Digital Radio Express eventually went out of business. References to the system generally end around 2013.

Description

The system is run from a singlerack unitbox called theX1 Encoder,which is actually based upon apersonal computer serveranddigital audiohardware fromLynx Studio Technologies(LST). Control is entirely viasoftware,viagigabit Ethernet,USB,serial port,andSVGA video monitor.All processing is handled internally by aPentium 4runningWindows XP.

FMeXtra is fully compatible withHD Radio,which uses additionalradio spectrumbeyond the ±100 kHz signal. It is not compatible with all existing subcarriers. Thus, a radio station might have to remove itsradio reading servicefor theblind,and replace it (and its dependent listeners' receivers) with a digital one. This would take up much lessbandwidth,particularly since voice can be highly compressed. The signal is partitioned so thatRBDS,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.

Thecodecsused areAACandaacPlusv1 and v2 andsample ratesof 8 kHz (telephone quality) to 96 kHz (surround soundquality). The othercodecsused areAMR-WB+that can create more multiple audio programs as well as limitedmultimediacan also be broadcast, as with HD Radio andDAB.The available broadcasting bandwidth for digital audio varies from 40kbit/swhile sharing the space with existing analog signals, or 156kbit/sif 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 highERPis 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 asVuCastin an effort to emphasize the technology'sdatacastingcapabilities.

Choosing a standard

North American FM bands are separated by 200 kHz while only using about 50 kHz for a high-quality stereo broadcast. This leaves significant amounts of unused spectrum between the channels. This unused spectrum led the FCC to strongly favor some sort of in-band standard for the digital transition. This is in contrast to European systems which use a similar amount of bandwidth for FM signals but typically separate the channels only 100 kHz. European stations favored moving to entirely new channels for digital broadcasts to avoid interfering with their existing FM signals.^[1]

Two systems were evaluated during the late 1990s, FMeXtra and HD Radio. From a purely technical perspective, HD Radio was more advanced than FMeXtra, using newer compression and encoding to allow the signals to be flexibly allocated into the existing channels. FMeXtra normally added a single 48 kbps digital channel carried in the 62.5-98.5 kHz area of the channel (just above the audio signal). HD Radio offered several different modes that used up more of the empty spectrum, providing 96 to 120 kbps. FMeXtra allowed one stream of "good" quality, two medium, or four mono low-quality signals suitable for talk radio. HD Radio offered one high-fidelity signal, better than FM, or several mixtures of medium quality.^[1]

Although HD Radio had superior technical capabilities (largely by using more bandwidth), FMeXtra was dramatically easier to implement. In the most common use-case, the existing FM signal would be fed into an FMeXtra encoder and then sent directly to the existing transmitter systems. The company did not charge any licensing, the only cost was the encoder box itself, around $10,000 when introduced. In contrast, HD Radio required a much more expensive encoder, about $50,000, generally required changes to the transmitter, and charged licensing fees on any additional channels.^[1]

As the standardization effort continued, broadcasters clearly favored HD Radio. This was not due to any technical issues specifically, but due to the way radio channels are monetized. Each channel runs advertising that pays for the system, so adding more signals to an existing radio system has significant financial benefits. With FMeXtra, the system normally broadcasts only the existing channel, which would result in no additional revenue. HD Radio would add additional channels, thus generating additional income.^[1]

In particular, HD Radio's ability to send one full-fidelity signal along with two or more signals of much higher quality than AM radio offered a significant practical benefit; those companies broadcasting on both FM and AM could move their AM stations to subchannels in their FM channels and turn off their AM transmitters. The combination of more channels and higher quality overwhelmed any financial benefit to FMeXtra's lower installation costs, and it was "left in the dust."^[1]

Stations broadcasting in FMeXtra

United States

and others

Minnesota Reading Services for the Blind has 25 FMeXtra encoders and 7,500 special FMeXtra receivers without a visual display.

Benelux

FMeXtra is not in use anymore in the BeNeLux. Short test where running on the following stations:^[3]^[4]

93.9Megastad,Rotterdam, The Netherlands, carrying Megastad Classics
96.5 Imagine FM, Brussels, Belgium, simulcast
98.4Radio 538,Goes, The Netherlands, carrying Radio 10 Gold & JuizeFM
100.4Q-music,Rotterdam & Oude Polder, The Netherlands, carrying Radio Bem Bem
100.7Q-music,Lopik, The Netherlands, carrying Radio Bem Bem
101.2Sky Radio,Hilversum, The Netherlands, carrying TMF Radio & Kink FM
101.9Radio 538,Alphen, The Netherlands, carrying Radio 10 Gold & JuizeFM
102.1Radio 538,Hilversum, The Netherlands, carrying Radio 10 Gold & JuizeFM
102.4Radio 538,Terneuzen, The Netherlands, carrying Radio 10 Gold & JuizeFM
102.7Radio 538,Rotterdam, The Netherlands, carrying Radio 10 Gold & JuizeFM
105.3Delta Radio,Twente, The Netherlands, carrying Delta Piraat
106.1Gold FM,Brussels, Belgium, simulcast + carrying Jet FM

Rest ofEurope

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

References

^^a ^b ^c ^d ^e"FMeXtra/VuCAST vs. HD Radio".Scientific Computing.27 October 2017.
^http://rwonline.com/dailynews/one.php?id=7993^{[permanent dead link‍]}
^"Online radio luisteren doe je via Radio.NL!".
^"Overzicht van alle FM zenders welke FMeXtra uit hebben gezonden in Nederland".

[fmx-1] "FMeXtra/VuCAST vs. HD Radio".Scientific Computing.27 October 2017.

[2] ttp://rwonline.com/dailynews/one.php?id=7993^{[permanent dead link‍]}

[3] "Online radio luisteren doe je via Radio.NL!".

[4] "Overzicht van alle FM zenders welke FMeXtra uit hebben gezonden in Nederland".

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