"Scott Dorsey" wrote in message
...
Ian Jackson wrote:
In message , Scott Dorsey writes:

Mine too, I don't really understand what you're asking. The crystal
filter
is a bandpass filter. The phasing control affects the symmetry of the
filter somewhat (but not really all that much).

The crystal by itself has a natural 'blow-suck' signal throughput, with a
sharp notch just HF of the peak. The phasing control capacitor should be
able to move the notch to the LF side of the peak, and also (to a limited
extent) to move the notch a little closer to the peak (on either side).

Yes, and that notch is useful for eliminating a single interfering CW
signal. But it's not useful for multiple interfering signals or much
at all for SSB.

"Single signal reception" to me would imply a narrow-sloped bandpass
filter but it sounds more like marketing than engineering.

Perhaps you, as indeed do others seem, are trying to interpret a technique
from
the 1930s and 1940s in terms of the multi-pole Xtal filters that are the
norm today?