To expand that a bit; many of the early SSB users used the military 
surplus BC459 as their VFO.  Central Electronics used this unit in a 
nice cabinet and most poor folks bought them for five bucks from 
radio military surplus stores.  in the mid and late fifties we had 
several blocks of those stores on the near South Side and what a 
bonanza they were for a kid with no money to speak of!!
I remember that the BC459 ran in the five megacycle range and as 
Butch described the output was used in such a way to generate 
sideband signals.  For sure the Central Electronics 10A,  10B and 20A 
SSB exciters all used this principle.  Those rigs ran ten and twenty 
watts respectively, came as kits or factory wired and weere pretty 
inexpensive.  They were "phasing" rigs and their unwanted sideband 
suppression wasn't terriffic but they got a lot of hams on sideband.
i got licensed in 1957 and my first band of operation was 160 
meters.  Then there were only 25 khz.of space and SSB and A M guys 
were really peeing all over one another about the space!!  Guess 
sideband ultimately won.
Sorry for the length of this!!
Pat, K9JAUAt 09:28 AM 10/14/2010, you wrote:
>I'm not sure, it is kind of like which came first the chicken or the egg.
>   Many early radios were designed in such a way that the 80 and 40 meter
>bands were derived by the difference frequencies between the vfo and
>mixer and the 20 15 and ten meter bands used the sum of the vfo plus
>oscillator.  Hope that makes sense.  If you remember theory, when you mix
>frequencies, such as a vfo plus oscillator you get on the output, both
>original frequencies plus sum and difference.  In my national ncx 200
>which was my first radio, the if as I recall was 5.2020 and the vfo was
>somewhere around 9 mhz.  Anyhow, when your mixing a signal and one of
>them is ssb, if you use the sum, the sideband stays the same, and if you
>use the difference such as my national did for 80 and 40, you get the
>opposite side band.
>73
>Butch Bussen
>wa0vjr
>open Node 3148
>Las Vegas
>
>
>On Wed, 13 Oct 2010, Phil Scovell wrote:
>
> > I think I heard once but I can't remember so does anyone know why the =
> > various bands are used for upper and lower side band?  Just curious.  =
> > There's got to be a reason why it is different based upon the band you =
> > are using.
> >
> > Phil.
> > K0NX
> >
> >