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 Previous: ARRL President Haynie Helps Celebrate JARL's 75th Anniversary |  Next: In Brief |
Doug Smith, KF6DX, at the US end of the first transatlantic Amateur Radio digital HF QSO. Smith operated from the Ten-Tec radio room and used an Orion transceiver. [Eric Guinn, AC4LS, Photo]. |
NEWINGTON, CT, Dec 4, 2002--Radio communications pioneers Ten-Tec and Thales have announced that they've used an Amateur Radio linkup to span the Atlantic on HF digital voice for the first time. Ten-Tec's Doug Smith, KF6DX, and Thales' Didier Chulot, F5MJN, successfully transmitted and received HF digital speech signals November 22 between Paris, France, and Ten-Tec's Sevierville, Tennessee, headquarters.
"We view this as a significant accomplishment," said Smith. "Amateur Radio has long been at the forefront of technological development. It's nice to be able to show that our legacy is alive and well." Tests are being conducted under the auspices of ARRL's Digital Voice Working Group, which Smith chairs. A written report on the tests is due in January.
Calling it "a major breakthrough," a Ten-Tec news release said the two amateur stations "demonstrated the advantages of digital audio during the conversation, including noise-free, FM-like reception and the potential for simultaneous voice and data." The feat was accomplished using Ten-Tec transceivers and Thales Communications digital audio software. Operating as F8KGG, Chulot spoke with Smith for several minutes over the HF digital link, operating within a 3-kHz bandwidth. The contact occurred on 15 meters on 21,218 kHz.
"The rigs F5MJN and I used are unmodified," Smith said. "They are being used in
regular upper-sideband mode." AM or FM mode also would work, he added. No additional hardware
was required beyond the cables connecting the transceiver and the microphone to the PC sound card.
ARRL Digital Voice Working Group Chair and QEX Editor Doug Smith, KF6DX (left) and Cédric Demeure of Thales (formerly Thomson/CSF) get ready for the Digital Voice Forum at Dayton Hamvention last May. |
Smith said signal strengths were S5 to S7 and readability was R5 in both directions. In terms of audio quality, Smith recorded a "mean opinion score" (MOS) of 3.5 out of a possible 5 in the QPSK mode, which runs at 1200 bits/sec. An MOS of 3 is generally defined as toll-quality--roughly the same as conventional telephone audio quality. Signals were also exchanged in 16-QAM mode at 2400 bits/sec.
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The Ten-Tec/Thales system is based on a new international broadcasting standard adopted last year by the International Telecommunication Union (ITU). Digital broadcast signals occupy up to 10 kHz of bandwidth. The FCC has approved a similar standard for AM broadcasting in the US called "In-Band, On-Channel" or IBOC. An Amateur Radio version of the Thales system is expected to appear on the market early next year, but Smith says he has no information on the software's cost or distribution.
"At this stage, the system is experimental-only for ham radio, but it looks like it's going to take off," Smith predicted.
In the US, Smith used the new Ten-Tec Orion HF transceiver at 100 W output coupled to a Hy-Gain
TH7DX tri-band Yagi at the Ten-Tec factory. In France, F5MJN operating F8KGG, used a Ten-Tec
Jupiter running 100 W to a log-periodic antenna.
A screen capture of the Thales Skywave 2000 software. |
Smith says that simultaneous digital voice and data over radio already are finding favor in public service circles. "Many law enforcement and emergency organizations have gone over to digital radios for secure and reliable digital communications," he said. "In addition, high-definition digital television (HDTV) systems that use digital audio are already in operation in many areas of the world." And, he points out, satellite-based digital audio broadcasting (DAB) began last year in earnest.
In terms of Amateur Radio digital equipment, Alinco was the first manufacturer to come out with a digital voice option (the EJ40U and EJ-43U) for some of its transceivers, including the DJ-596 hand-held and four of its mobile units, including the recently released DR-620T dualbander.
ICOM debuted its D-Star digital "concept radio" system last May at the Dayton Hamvention--where Smith chaired the Digital Voice Forum--and demonstrated it at the ARRL-TAPR Digital Communications Conference in September. The unit, which operates on 1.2 GHz, was scheduled to hit the ham radio market this fall. At its heart is the ID-1 transceiver, which can communicate using FM analog voice, digital voice and data.
Smith says the technical details of the Thales system will appear in an article. "International Digital Audio Broadcasting Standards: Voice Coding and Amateur Radio Applications" in the January/February issue of QEX, which he edits. He also has authored two articles on digital voice in QST: "Digital Voice: The Next New Mode?," in the January 2002 issue, and "Digital Voice: An Update and Forecast," in the February 2002 issue. All of these are available on the ARRLWeb Digital Voice page.
Additional images and background are available on the TAPR Web site. Look for the Digital Voice Forum page and the presentation by Cédric Demeure.--Ten-Tec news release; Doug Smith, KF6DX
A Brief Digital HistoryWork on digital audio began with the telephone at Bell Labs more than 50 years ago, and virtually every wireline telephone conversation today uses digital signals. "Early on, Bell engineers realized it is better to transmit and receive information in binary form than in regular analog form," says ARRL Digital Working Group Chairman Doug Smith, KF6DX. He explains that digital technique, which basically relies on determining the difference between "on" and "off" states, is easier to detect over noisy communications circuits than an analog signal representing the continuous fluctuations of a person's voice, which may take on a vast number of states. In the 1960s, the National Aeronautics and Space Administration (NASA) adopted digital audio for Project Apollo. The system, developed by the Radio Corporation of America (RCA), also incorporated a ranging feature that allowed astronauts to determine the distance between transmitter and receiver. Audio quality was robust. Smith said. Today's cellular telephones and space communications use sophisticated digital audio coding techniques. Digital audio and video have created a revolution in Internet communications, as well. As even most non-technical consumers know, the recording industry employs digital techniques in CDs and DVDs for the retail market.
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