[Milsurplus] Crystal filter question(s)

[Bill Cromwell]

Hi Clete,

No disagreements from me. The part of our posts regarding the change in
shape of the passband is a matter of semantics really. If you sweep the
response when the phasing control has the notch at the crystal response
peak then that point is below the top of the curve at the points on one
or both sides of it. The crystal response didn't shift its center
frequency but the shape of the system response curve, with the notch at
the crystal peak makes it look that way. The system response curve and
the crystal response curve are a little different.

My comment about the crystal controlled BFO was mostly to reinforce the
idea that the filter system is stable. Obviously a stable variable BFO
is more useful for people who know how to use one. In a simple rig meant
for field operations a crystal controlled BFO can reduce parts counts,
reduce the size of the receiver, and simplify operation. I wouldn't
replace an existing variable VFO with a crystal oscillator. So again, I
am encouraging hams to consider use of receivers with these filters or
add them to projects.

73,

Bill  KU8H