[Elecraft] Elecraft Digest, Vol 49, Issue 52

[Ian White GM3SEK]

WILLIS COOKE wrote:
>It does not give the same sideband on 80 and 20.  You also have to 
>consider that the rotation of the tuning capacitor of the VFO turns the 
>opposite direction for 20 as it does  for 80.

The direction of tuning is not what inverts the sideband.

The only thing that inverts the sideband is if the SSB frequency is 
subtracted in the mixing process. So:

9MHz USB + 5MHz VFO = 14MHz USB

9MHz USB - 5MHz VFO = 4MHz USB - sideband is not inverted.

But in Norgaard's 'New Approach to SBB Generation' in QST, June 1948, 
the SSB is generated on 5MHz and the VFO is around 9MHz, so:

9MHz VFO + 5MHz USB = 14MHz USB

9MHz VFO minus 5MHz USB = 4MHz **LSB** - now the sideband is inverted.

If anyone is still in doubt about this, words aren't going to help any 
more. Please take a few minutes with a pencil and a calculator, punch in 
some numbers and verify it for yourself.


-- 

73 from Ian GM3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek