Butch,
Doesn't it all go back to the Central Electronics exciters and BC459 
surplus VFOs and phasing exciters?  About the only thing out there 
when I got started.
Pat, K9JAUAt 02:08 PM 4/1/2015, you wrote:
>Shouldn't be any difference as far as noise.  AS far as near band edge, if
>you say are on 3.998, 2kc down from 4.00, your transmitted energy is below
>that on lower side band.  If you switch side bands, you're roughly 3 kc
>above and anything  above 2 kc puts you out of band.  When you switched
>side bands on older rigs, some switched filters and others switched the
>crystal in the carrier oscilator.  If crystals were switched, you actually
>moved frequency on receive and transmit because the output of that circuit
>is switched.  Hope that makes sense.
>73
>Butch
>WA0VJR
>Node 3148
>Wallace, ks.