Spring 2008 Issue

Digital Radio
Digital Technology on VHF, UHF, and Microwaves

Digital Voice and Data Modes The Way Forward

By Mark Thompson, WB9QZB

I recently was recently asked by Joe Lynch, N6CL, the Editor of CQ VHF magazine, to do a column about digital technology on VHF, UHF, and the microwave bands. I have experience writing many editorials over the last 20 years for the “RAIN Report.” I decided that with the help of the digital ham community there is an important role for this new column.

First, a little background about me: I was first licensed in 1975 in Wisconsin. I am an active ham who reads all of the ham radio publications and belongs to three radio clubs in the Chicago area. I also attend the Dayton Hamvention® every year.

I first became interested in digital technology in the late 1970s while a student at the University of Wisconsin, Madison. Our student ham radio club was given a Teletype Model 15 that we cleaned and adjusted. We got the loop current for the Model 15 from a Johnson T/R switch we were no longer using. We then acquired a HAL ST-5000 terminal unit that we used on both HF and 2-meter auto-start. The Model 15 handled only the Baudot format of RTTY.

In the mid 1980s I bought my first Kantronics TNC (terminal node controller) and became active in packet radio. I became involved with the Chicago Area Packet Radio Association (CAPRA) and I founded a separate packet radio frequency coordination group. CAPRA was a very active club and built many of the packet radio networks in the Chicago area in the 1990s. In 1998 Carl Bergstedt, K9VXW, and I, along with CAPRA, were the co-hosts for the ARRL/TAPR DCC (Digital Communications Conference) in Chicago. We will host the 2008 DCC in Chicago in September. There will be more about the DCC in a future column.

At the Dayton Hamvention® in 2004 and 2005, I noticed the new D-STAR digital voice and data technology at the ICOM booth. In early 2006 I became more interested in D-STAR. I educated myself about the technology and met and talked with hams who have been experimenting with and deploying the technology. Although I had given many presentations in my work, I had never given a presentation to a ham radio group. In spring 2006 I began to give D-STAR Introduction/Overview presentations at ham club meetings and hamfests in northern Illinois, southern Wisconsin, and northern Indiana. The presentations were well received, with large attendance. There is a great deal of interest in digital voice. During 11/2 years I have given over three dozen presentations and met many hams. In addition, I have been directly involved with the deployment of D-STAR technology in the Chicago area.

A year and a half ago I started a new Yahoo group focusing on digital voice and data technologies. Entitled the “illinoisdigitalham,” the group has dozens of files and links covering all the digital ham modes and now has approximately 2400 members. More information on the group can be found at: <http://groups.yahoo. com/group/illinoisdigitalham>. As its moderator, it has given me exposure to many digital technologies and different points of view.

History of Digital Modes

For most of the history of ham radio digital has meant data. RTTY Baudot and then RTTY ASCII were the mainstay of digital until AX.25 packet radio was developed in the early 1980s. The packet radio TNC (terminal node controllers) led to multi-mode controllers that could handle CW, packet, AMTOR, RTTY, and other modes.

These multi-mode controllers were quite popular until the sound-card modes such as PSK, MFSK, Olivia, etc., were developed. Sound-card modes run on any Windows® PC using the PC’s sound-card and require an interface to the radio. Several firms have developed interface units to allow connection to the radio with the correct cable. Both packet radio and the sound-card modes are backward compatible with existing analog radios in that they operate on FM and SSB radios. Sound-card modes can transmit and receive both voice and data.

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