[Elecraft] OT: USB and LSB - How we got there

[Fred Jensen]

I have a vague recollection from the early 50s [all recollections from 
then are vague] that sideband generation at 5 MHz became popular as 
phasing rigs began to give way to filter rigs and for some reason, 
crystals in the 5 MHz region were more plentiful and cheaper. ???  The 
"9 and 5" scheme gave you 20 and 80 [and I'm not sure when phone on 40 
was authorized in the US], but rigs such as the Swan 500 in the early 
60's generated SSB at 5.500 MHz with additional VFO frequencies to hit 
40, 15, and 10 as well.

I was originally licensed in '53 but had been listening since mid '51 
and the "LSB below 10 Mcs, USB above" convention was thoroughly and 
firmly established by then.  Nice to know where it came from.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 2/15/2018 3:27 AM, Ian White wrote:
> 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-bounces at mailman.qth.net [mailto:elecraft-
>> bounces at mailman.qth.net] On Behalf Of Ian White
>> Sent: 15 February 2018 10:11
>> To: 'Alan'; elecraft at 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 at 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 k6dgw at foothill.net
>