[Elecraft] Fw: ESSB

[Alan Bloom]

On Mon, 2011-04-25 at 21:08 -0400, riese-k3djc at juno.com wrote:
> Try to make me understand why you would use ESSB
> 
> Bob K3DJC>

I use it with the bandwidth set to minimum (3 kHz) and the TX equalizer
set to limit the transmitted bandwidth to about what it would be using
regular SSB.  I do that to get better, more natural-sounding transmitted
audio.

Audio quality is not only, or even mainly, determined by the bandwidth
and amplitude flatness.  The phase response is critical.  If you look at
a crystal filter on a vector network analyzer you can easily see that
the phase response is very non-linear.  A "good" crystal filter with a
small shape factor (large number of poles) is worse in this respect than
a cheaper filter with a poorer shape factor.

I believe the un-natural sound of most SSB signals is primarily due to
the non-linear phase of the crystal filters.

ESSB uses the 6 kHz crystal filter, which has a smoother phase response.
The transmitted bandwidth is limited by the digital filter, which is
inherently linear-phase and contributes no additional phase distortion.

Alan N1AL