"Ken Scharf" wrote in message
. ..
I have about a half dozen 3.333mhz and 5.0688 crystals.
Each group is with in 100hz of the same frequency when
put into a simple oscillator. I also have a few 11.0592
crystals that are almost as close (probably should get
a few more of these). The 5.0688 and 11.0592 are in
HC49/U cans, the 3.333 are in a somewhat larger sized
can.

Wonder if any of these groups would make a good ladder
filter for a receiver IF strip? I would guess the 3.333
ones would be better for CW, the 11.0592 for ssb, and
the 5.0688 might be a compromise either way?

There's a good article about building ladder filters in QRP Power. Designing
and Building High-Performance Crystal Ladder Filters by Mahkinson, N6NWP.
Was originally in QEX for Jan 1995. QRP Power also reprints an article by
W7ZOI, Refinements in Crystal Ladder Filter Design, from June 1995 QEX.

Mahkinson says "Unfortunately, the required termination resistances of
filters built with [color-burst] crystals may exceed 10k ohms, which
necessitates an impedance transformation with a very high ratio (for a
50-ohm system.). As a result, very high voltage levels may be developed at
the filter input, which may cause an overload condition. In addition, the
required values of the coupling capacitors may be under 5 pF, making
construction difficult due to stray capacitances. For these reasons, crystal
filters with center frequencies under 6 MHz are not recommended."

"The usef ful upper frequency limit is determined by the influence of stray
capacitances at frequencies above 10 MHz and by the limitations imposed on
the VFO circuit for multiband HF operation. Consequently, the recommended
frequency range for an HF SSB crystal filter is between 6 and 12 MHz.: The
remaining criteria for the crystal frequency selection are the crystal Q and
the price."

73,

"PM"