Winter 2006 Issue

FM

D-STAR Digital Voice for VHF/UHF

By Bob Witte, KØNR

VHF/UHF D-STAR radios are making their way into the U.S. ham radio community. What is this new technology and how will it benefit the ham radio enthusiast?

Digital Modulation

Unless you were unconscious for the last two decades, you have noticed that digital technology has swept through most types of electronic devices, creating more capability and changing primarily analog devices into digital wonders. Analog music media such as the conventional LP record and magnetic tape have been replaced by digitally-encoded CD-ROMs. More recently, the rise of the Internet and digital audio formats (e.g., MP3) has changed how music is created and distributed. Closer to home for ham radio enthusiasts, the cellular telephone, originally deployed with analog FM technology, has largely migrated to digital-modulation techniques. Digital technology allows mobile-phone service providers to provide cost-effective voice communications while adding services such as text messaging and web surfing, all while improving the spectral efficiency of their networks.

Meanwhile, those of us who enjoy using FM simplex and repeaters on the VHF and higher amateur bands are still using good old analog FM. Edwin H. Armstrong first described the use of frequency modulation in 1936.1 The first practical two-way FM radio-telephone mobile system in the world was implemented in 1940 for the Connecticut State Police. Let’s consider 1940 the start of what we know today as two-way FM radio. That was 65 years ago! Perhaps it is time to move to new technology.

We have already seen digital technology wiggle its way into our inherently analog radios. Modern FM transceivers have digitally-synthesized frequency control circuits, digital storage of channel information, serial ports for loading configurations, and computer software to control these rigs. Packet radio uses AX.25 digital protocols to provide an error-free data transmission mechanism, but the underlying modulation generally is still analog FM. The next step may be a truly integrated approach to voice and data.

Photo A. The ICOM IC-2200H is a conventional 2-meter FM transceiver with D-STAR digital operation available as an option. (Photo courtesy of ICOM America)

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