There are several enhancements to terrestrial radio that HD Radio offers, and each has its own merits to help further the technology and its acceptance. Despite these enhancements, many stations have difficulty identifying the return on investment. But for one FM enhancement, the return is obvious.

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Multicasting, the ability to transmit more than one program stream on the FM HD Radio path, is one enhancement that can show a direct result right now. The added program streams are an immediate outlet for an additional revenue stream. And while the main program stream provides the main source of revenue, multicast stream formats can be tested and evaluated with little effort at the start.

In February, the 1,000^th multicast stream was turned on. According to the HD Digital Radio Alliance, CBS-owned WODS-FM Boston launched the 1,000th multicast stream on its HD2 with the format Soft Hits - Love Songs. But there are more statistics related to multicasting than the overall quantity.

There are currently nearly 1,900 stations transmitting an HD Radio signal. Of those, almost 300 are AM stations. The 1,000 multicast streams are spread across 1,600 FM stations.

The Ibiquity website lists all the stations currently transmitting HD Radio signals, and according to this list, of the 1,000 multicasts 900 of them are on HD2 signals. The remainder are on HD3 slots. The Ibiquity list shows no multicasts on HD3 channels.

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The first multicast streams were launched at the end of 2004. By the end of 2005, there were 21 multicast streams. The multicast adoption has seen a steady increase ever since, albeit with a few growth spurts. The 250^th stream went live in April 2006. The 500^th stream was activated in November 2006, and the 750^th stream was launched in October 2007.

Multicast formats span a variety of formats. Many of them are unique niches in some way, such as deep cuts, all live, all acoustic or other similarly focused aspects of a traditional radio format. Some multicast streams are rebroadcasts of AM stations. The BBC World Service and NPR programs are also popular multicast offerings.

So with 1,000 multicast streams and counting, it appears that it has established a firm foot hold.

Data for charts courtesy of Ibiquity Digital and the HD Digital Radio Alliance.