Hello all, Can anybody tell the key motivation of the inventor (who is the genius behind it?) to use digital modulation instead of its analog counterpart and how did it happen historically and experimentally? Regards, Santosh
Digital modulation!!
Started by ●July 7, 2003
Reply by ●July 7, 20032003-07-07
"santosh nath" <santosh.nath@ntlworld.com> ha scritto nel messaggio news:6afd943a.0307071009.1dc4432c@posting.google.com...> Hello all, > Can anybody tell the key motivation of the inventor (who is the > genius behind it?) to use digital modulation instead of its analog > counterpart and how did it happen historically and experimentally?that's a nice question. There are many fathers behind digital transmission, but mabye the greatest is Shannon. I'm also proud of being born in the same country as Mr.Andrea/Andrew Viterbi!
Reply by ●July 7, 20032003-07-07
"Ema" <ziglio@people.it> wrote in message news:3ajOa.7240$79.141342@tornado.fastwebnet.it...> "santosh nath" <santosh.nath@ntlworld.com> ha scritto nel messaggio > news:6afd943a.0307071009.1dc4432c@posting.google.com... > > Hello all, > > Can anybody tell the key motivation of the inventor (who is the > > genius behind it?) to use digital modulation instead of its analog > > counterpart and how did it happen historically and experimentally? > > that's a nice question. > There are many fathers behind digital transmission, but mabye the greatest > is Shannon. > I'm also proud of being born in the same country as Mr.Andrea/Andrew > Viterbi!Hmmm. Digital modulation is older than analog. The Morse telegraph is older than the Bell telephone. Digital modulated radio transmission is older than analog (voice) radio. The reason is that it is easier to do. Be sure to credit the newsgroup and/or Google (tm) on your homework paper. -- glen
Reply by ●July 7, 20032003-07-07
santosh nath wrote:> > Hello all, > Can anybody tell the key motivation of the inventor (who is the > genius behind it?) to use digital modulation instead of its analog > counterpart and how did it happen historically and experimentally? > > Regards, > SantoshIf you define what you mean by "digital modulation", perhaps the information you crave resides somewhere in my hoary head. Off hand, I can't think of any digital modulation scheme that produces the same RF signal made by an analog method. There are at least three kinds of of early modulation that I would characterize as "digital". In one, the current-on/current-off pulses used by Baudot (it requires the same kind of DC connection used for telegraphy) was translated to a pair of tones so it could be sent over the switched voice network. That was a natural extension of the idea of turning an RF carrier on and off to transmit telegraph code, and the origin of the modem. The first radio-telegraph transmissions used spark-gap transmitters, so no tone generator at the receiver was needed. Later, with CW transmitters, a BFO was needed in the receiver. Another broad class has pulse-width- and pulse-position modulation as members. For data sampled as numbers, pulse code modulation is standard. The number of different ways that's done nowadays is mind boggling. Come to think of it, Baudot Teletype are pulse-code modulation. The codes represent letters and symbols, rather than numbers as such. That kind of digital modulation predates the widespread use of vacuum tubes. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●July 7, 20032003-07-07
"Ema" <ziglio@people.it> wrote in message news:<3ajOa.7240$79.141342@tornado.fastwebnet.it>...> "santosh nath" <santosh.nath@ntlworld.com> ha scritto nel messaggio > news:6afd943a.0307071009.1dc4432c@posting.google.com... > > Hello all, > > Can anybody tell the key motivation of the inventor (who is the > > genius behind it?) to use digital modulation instead of its analog > > counterpart and how did it happen historically and experimentally? > > that's a nice question. > There are many fathers behind digital transmission, but mabye the greatest > is Shannon. > I'm also proud of being born in the same country as Mr.Andrea/Andrew > Viterbi!I guess Shannon is the father of information theory , digital communication and many more - he is a real genius and unparallel figure of all time! One name came into my mind as the inventor of digital modulation like PCM dated back in 1939 by Alec H. Reeves, an English inventor. But I am very interested to know how he or others approached ; what the motivation and observation were behind it- sorry to repeat the question again? Regards, Santosh
Reply by ●July 7, 20032003-07-07
"Jerry Avins" <jya@ieee.org> wrote in message news:3F09E193.7EF86612@ieee.org...> santosh nath wrote: > >(snip)> There are at least three kinds of of early modulation that I would > characterize as "digital". In one, the current-on/current-off pulses > used by Baudot (it requires the same kind of DC connection used for > telegraphy) was translated to a pair of tones so it could be sent over > the switched voice network. That was a natural extension of the idea of > turning an RF carrier on and off to transmit telegraph code, and the > origin of the modem. The first radio-telegraph transmissions used > spark-gap transmitters, so no tone generator at the receiver was needed. > Later, with CW transmitters, a BFO was needed in the receiver.I seem to remember stories about the beginnings of analog radio. Before that, as you indicate, no demodulation was needed. Headphones were directly connected to the output, and used to receive Morse code. So when analog (voice) radio started people were surprised to hear voice where they previously heard only Morse code. There there is another story, from slightly later but still in the days when most people used headphones to listen to their radio receivers. Someone found that their radio still worked with one part removed, so they kept removing parts until it stopped. Eventually finding out that their neighbor had just bought a receiver with a loudspeaker, which is what they were listening to. -- glen
Reply by ●July 7, 20032003-07-07
"santosh nath" <santosh.nath@ntlworld.com> wrote in message news:6afd943a.0307071009.1dc4432c@posting.google.com...> Hello all, > Can anybody tell the key motivation of the inventor (who is the > genius behind it?) to use digital modulation instead of its analog > counterpart and how did it happen historically and experimentally? > > Regards, > SantoshAccording to Black in Modulation Theory, one of the Bell Labs Series books, "...as proposed much earlier (1758) by a Scot named Marshall and often considered the first practical telegrahy scheme." Other readings suggest that Marshall wasn't the first or that it wasn't Marshall, etc..... Fred (of the same Scots name) :-)
Reply by ●July 8, 20032003-07-08
"santosh nath" <santosh.nath@ntlworld.com> wrote in message news:6afd943a.0307071349.32b2f74a@posting.google.com...> "Ema" <ziglio@people.it> wrote in messagenews:<3ajOa.7240$79.141342@tornado.fastwebnet.it>...> > "santosh nath" <santosh.nath@ntlworld.com> ha scritto nel messaggio > > news:6afd943a.0307071009.1dc4432c@posting.google.com... > > > Hello all, > > > Can anybody tell the key motivation of the inventor (who is the > > > genius behind it?) to use digital modulation instead of its analog > > > counterpart and how did it happen historically and experimentally? > > > > that's a nice question. > > There are many fathers behind digital transmission, but mabye thegreatest> > is Shannon. > > I'm also proud of being born in the same country as Mr.Andrea/Andrew > > Viterbi! > > I guess Shannon is the father of information theory , digital > communication > and many more - he is a real genius and unparallel figure of all time! > > One name came into my mind as the inventor of digital modulation like > PCM > dated back in 1939 by Alec H. Reeves, an English inventor. But I am > very interested to know how he or others approached ; what the > motivation and observation were behind it- sorry to repeat the > question again?John de Rivaz should still be around and is/was Reeves Telecom Labs in Cornwall - he worked with Alec Reeves. You should be able to find him with a web search. He and his missus are into freezing themselves when they die for resurrection at some time in the future. Leon -- Leon Heller, G1HSM leon_heller@hotmail.com http://www.geocities.com/leon_heller
Reply by ●July 8, 20032003-07-08
santosh nath wrote:>...> > I guess Shannon is the father of information theory , digital > communication > and many more - he is a real genius and unparallel figure of all time! >... Hero worship is likely to warp one's perspective. The first digital communications systems I know much about were Napoleon's wig-wag telegraph with left and right standing for one and zero, and Amerindian smoke signals, which were made by moving a blanket ON and OFF. As Glen wrote, digital modulation came first because it's easier. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●July 8, 20032003-07-08
Glen Herrmannsfeldt wrote:> > "Jerry Avins" <jya@ieee.org> wrote in message > news:3F09E193.7EF86612@ieee.org... > > santosh nath wrote: > > > > > (snip) > > > There are at least three kinds of of early modulation that I would > > characterize as "digital". In one, the current-on/current-off pulses > > used by Baudot (it requires the same kind of DC connection used for > > telegraphy) was translated to a pair of tones so it could be sent over > > the switched voice network. That was a natural extension of the idea of > > turning an RF carrier on and off to transmit telegraph code, and the > > origin of the modem. The first radio-telegraph transmissions used > > spark-gap transmitters, so no tone generator at the receiver was needed. > > Later, with CW transmitters, a BFO was needed in the receiver. > > I seem to remember stories about the beginnings of analog radio. Before > that, as you indicate, no demodulation was needed. Headphones were directly > connected to the output, and used to receive Morse code. So when analog > (voice) radio started people were surprised to hear voice where they > previously heard only Morse code. > > There there is another story, from slightly later but still in the days when > most people used headphones to listen to their radio receivers. Someone > found that their radio still worked with one part removed, so they kept > removing parts until it stopped. Eventually finding out that their neighbor > had just bought a receiver with a loudspeaker, which is what they were > listening to. > > -- glenHe might have been in a family friend's barn. When inside, or outside near one wall, a local radio station was clearly audible. The copper gutter and leader were the antenna, and a copper/copper-oxide junction in the joint between them was the rectifier. The currents were large enough to cause the wall to vibrate, and that was that. I gave the cows some rest with a piece of braid. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
