The 5.2 MHz SSB exciter construction article that Ian referred to in January 1949 QST is here:
http://p1k.arrl.org/pubs_archive/29327 73 Frank W3LPL ----- Original Message ----- From: donov...@starpower.net To: elecraft@mailman.qth.net Sent: Thursday, February 15, 2018 5:17:57 PM Subject: Re: [Elecraft] OT: USB and LSB - How we got there Thanks Ian, very interesting reading! http://p1k.arrl.org/pubs_archive/28966 73 Frank W3LPL ----- Original Message ----- From: "Ian White" <gm3...@ifwtech.co.uk> To: elecraft@mailman.qth.net Sent: Thursday, February 15, 2018 11:27:15 AM Subject: Re: [Elecraft] OT: USB and LSB - How we got there Clarification: W2KUJ first published the design concept for a 20/80m SSB exciter using 5MHz SSB generation and a 9MHz VFO, in QST for June 1948. W1DX then expanded W2KUJ's block-diagram concept into a practical design for others to copy, and this was published in January 1949. 73 from Ian GM3SEK >-----Original Message----- >From: elecraft-boun...@mailman.qth.net [mailto:elecraft- >boun...@mailman.qth.net] On Behalf Of Ian White >Sent: 15 February 2018 10:11 >To: 'Alan'; elecraft@mailman.qth.net >Subject: Re: [Elecraft] OT: USB and LSB - How we got there > > >In 2003 I researched the subject for my RSGB Q&A column, 'In >Practice', and was fortunate to be in contact with some amateurs who >were personally involved in the decision to switch sidebands at >10MHz. This decision was made in April 1952 and eventually became >an >IARU standard - but its origins are surprisingly technical. The >standard came out of two totally unrelated design decisions, made by >different people on different continents, and at different times in >the late 1940s. > >Those post-war years saw a rapid development in intercontinental HF >telephone links. These links used independent-sideband (ISB) >modulation to carry two separate voice channels on opposite >sidebands, and a major manufacturer of ISB equipment at this time >was the Marconi company. The ISB signal was created by up- >converting >two separately generated USB and LSB voice channels to the same >suppressed carrier frequency, and the Marconi engineers made the >smart decision to generate the ISB signal on 10.000MHz (a frequency >on which they would never need to transmit, because it was already >occupied by beacons such as WWV). > >For transmitted frequencies above 10MHz, Marconi used a >crystal-controlled LO that was 10MHz below the output frequency; so >the IF frequency was added to the LO and the two independent >sidebands remained "the right way up". But for transmitted >frequencies *below* 10MHz, the LO frequency was 10MHz *above* >the >output frequency; so the IF frequency was *subtracted* from the LO >and the opposite sidebands were *inverted*. In an ISB system, that >meant that the two telephone channels might very easily become >swapped, so station engineers all around the world needed to be sure >when to flip the appropriate switches. > >Out of these working arrangements between engineers, a worldwide >CCIR standard emerged that 10MHz would be the frequency where the >sidebands in ISB systems changed over. > >So what has this to do with amateur SSB? Amateur development in the >late 1940s quickly followed the developments in commercial world - >and sometimes involved the same individuals. A major influence was >the W1DX SSB exciter, published in 1949, which automatically >produced a sideband inversion between 80m and 20m. The W1DX >design >used the phasing method which allowed easy sideband selection by >flipping a switch at AF, but by the early 1950s there were also many >filter-method exciters that were not so agile. > >By 1951-52, experimenters in Europe and the USA were beginning to >talk to each other on 20m, and quickly realised that they were >heading for a mess. Most people were using USB on 20m, but there >was >no international agreement on 80m... and what about the other >bands? >>From eyewitness accounts, April 1952 was the moment when the >agreement crystallized as we know it today. > >The two key points in this history are: amateurs were *already >aware* of the commercial dividing line at 10MHz; and the popular >W1DX exciter was *already compatible* with the new proposed >standard >[1]. > >And so it was that two entirely separate and obscure design >decisions - by Marconi engineers and by W1DX - came together to >create the standard that we have today. > > >[1] SSB exciters using 9MHz SSB generation and a 5MHz VFO are not >relevant to this history. They all came *after* the 10MHz standard >was already in place. > >73 from Ian GM3SEK > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to donov...@starpower.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to donov...@starpower.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
