Another recent post by Don Wilhem as to commercial use of only USB is correct and has always "been" to my recollection. A bit of a history lesson is in order here. The use of LSB on 75 meters and USB on 20 meters (there was NO 40 meter voice band at the time!) in all probability is a phenomenon started by a "phasing" exciter known as the "SSB Jr." and it's derivatives, the most famous one being the Central Electronics Model 10A, then the model 10B and 20A which were possibly the most popular "factory made" transmitters at the time. All these exciters had no USB and LSB markings on the mode switch, but they were designated "SB1" and SB2". The reason this was done was due to the conversion process employed as the SSB signal was generated at 9 Mhz and heterodyned to either 14, or 4 Mhz with a 5 MHz VFO signal. Whichever position of the mode switch was used (SB1 in all probability, it's been too many years for me to precisely recall and not really important at this time for me to research it!) At any rate, the result was Upper sideband signals on 14 Mhz and lower sideband signals at 3.8-4.0 Mhz. Why switch the switch when changing bands to maintain the "same" sideband? Laziness prevailed! "Convention started" (LSB on 75, USB on 20) continued on 10 and later 15 meters by the use of USB and when voice was permitted on 40 meters, LSB there. The "tradition" has continued thru the present day. Commercial SSB has ALWAYS been upper, used extensively for Shipboard and aeronautical HF communication ever since. Some "Fixed" HF communications have made use of "ISB" in which the lower and upper sidebands carried simultaneously independent information on the two sidebands. In this case "lower" is utilized. It is rather difficult to get a radio receiver built for commercial use that is actually fitted with a "Lower sideband" filter unit! Many very fine receivers used in the maritime service are almost, if not impossible to actually find a "filter module" for to enable "LSB" use!
Government users almost ALWAYS utilize Upper Sideband, hence the use of it on 60 meters where the Amateur Service is a "secondary user" of the spectrum space. Hope this clears up the WHYS of upper on high bands and lower on lower bands and why it started. My information is what I recall years ago, so don't hold me responsible for small errors or minute details about the why's and when's! 73, Sandy W5TVW -----Original Message----- From: Kevin Cozens Sent: Tuesday, November 22, 2011 10:54 AM To: K2 Subject: Re: [Elecraft] US 60 Meter Band Changes Approved by FCC On 11-11-19 02:36 PM, Mike Morrow wrote: > Yesterday (18 November 2011), the FCC published its approval of changes > to the US 60 meter band. [snip] > (3) Three emission modes (CW, RTTY, Data) are authorized in addition to > the existing USB mode. Is that a typo at the end of (3) above? It would be a break with (amateur radio) convention to use USB in that part of the radio spectrum. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.1873 / Virus Database: 2101/4630 - Release Date: 11/21/11 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
