Doug-Smith.net
Title
Douglas T. Smith Editorial Services: Digital Signal Processing Technology
Description
QEX Editor Doug Smith, KF6DX, has announced a speaking tour for 2005 that includes the ARRL National Convention at the Dayton Hamvention in Trotwood, Ohio. The Convention runs May 20-22 at Hara Arena. Visit http://www.doug-smith.net for details.
Two radio communications pioneers recently achieved a major breakthrough: the first two-way digital voice transmission across the Atlantic via Amateur Radio. Doug Smith, KF6DX, and Didier Chulot, F5MJN, successfully transmitted and received HF digital speech signals on Friday, November 22, 2002 between here and Paris, France.
The feat was accomplished using Ten-Tec transceivers and digital audio systems from Thales Communications (pronounced "tall'-ess") in Paris. Operating station F8KGG, Chulot spoke with Smith for several minutes using the high-frequency digital link, operating within a 3-kHz bandwidth. The contact occurred on 15 m. Signal strengths were S-5 to S-7 and readability was 5 in both directions. A mean opinion score (MOS) of 3.5 of a possible 5 for audio quality was recorded by KF6DX in the QPSK mode, which runs at 1200 bits/sec. An MOS of 3 is generally defined as "toll-quality," or roughly the same as what a telephone produces. Signals were also exchanged in 16-QAM mode at 2400 bits/sec. The two stations demonstrated the advantages of digital audio during the conversation, including noise-free, FM-like reception and the potential for simultaneous voice and data.
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