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On Wed, 25 Feb 2015, Stephen Thomas Cole wrote:
Michael Black wrote: On Tue, 24 Feb 2015, gareth wrote: What is the point of digital voice when there are already AM, SSB and FM for those who want to appear indistinguishable from CBers? Perhaps it is cynicism from the manufacturers who introduce such things as they see their traditional highly-priced corner of the market being wiped away by SDR technologies? Because it's something new, at least to amateur radio. The phasing method of sideband was common in the early days of amateur SSB (I recall reading the first rigs were filter type, but with really low IFs, then phasing, then crystal and mechanical filters took over from phasing). It offered up a lot on transmit and receive, though not perfection. But now phasing is used a lot, because digital circuitry has made it viable. I remember seeing some of the potential when phasing was still analog, but I also remember reading articles where it was clear others didn't see the potential. Sometimes ideas become lost when something becomes commonplace. Who knows what would come from digital voice. But I remember 30 years ago one local ham being interested in it, not to the extent of putting something on the air, but as information from the computer world started flowing in, the potential started being there. YOu can't resist new things and say "they have no use", you have to embrace the new and see what can be done with it. Maybe not as initially seen, but maybe it fits in somewhere else. Amateur radio has never done much with envelope elimination and restoration (was that what it was called? I now forget). It's in one of the sideband books, and Karl Meinzer of AMSAT fame wrote about it in QST about 1970. Break the SSB signal into two components, so you can multiply it up to a higher frequency, then modulate the output stage. If you have an efficient modulator, you can do away with linear amplifiers (which is why it was in that SSB book). I gather he used the scheme in at least one of the amateur satellites after Oscar 6. But what happens in the digital age? Can you generate the two streems, in essence but not so simple an FM component and an AM component, without needing to generate SSB and then extract the two streams? I don't know, but so much digital processing is being done now, it may be something to look into. With solid state devices and class D amplifiers, modulating high level class C amplifiers can't be as much trouble as in the old days. Maybe it amounts to nothing, but maybe it overall becomes more efficient, if it can be done. Maybe there's no value to digital voice, except that in the process of learnign about it, and implementing it, one can learn something. Maybe something merely new to the person learning, but maybe something completely new. No advances are made without learning, the learning triggers new advances. Michael You do realise that you're responding to a troll post, right? Only because you continue to keep that war going even as it spills out of the UK newsgroup. I didnt' "feed the troll", you do that all the time by keeping up the vendetta. I chose to say something about the topic, certainly about how ideas advance, and it exists whether or not he is a troll. Michael |
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