Updated 4-30-08.  Update page to describe construction of different filters, all commonly using the same PWB, part number: PWB-MCF.

    This page will describe the common PWB-MCF and various SLIM crystal filters that can be constructed on this pwb.  The SLIM-MCF-xxxx are "place holders" until a good, reputable monolithic crystal can be identified and a supplier found.

PWB-MCF, pwb for Monolithic Crystal Filter, size-A
    The PWB-MCF is a generic printed wiring board design that will accommodate a variety of multipole, Monolithic Crystal Filters.  The board is split into two sections with a short fence as a separator.

Artwork for pwb, and parts locator for SLIM-MCF-xxxx

     PWB-MCF rev A, Base artwork for PWB, in ExpressPCB software.  Use this drawing to order the pwb from Express, or to locate the parts for a generic filter.
    There are no board vias designed to accomodate a specific filter.  The idea is to drill holes for the filter leads and solder the filter on the bottom side of the pwb.  The filter is mounted on the bottom side of the pwb with the leads extending through to the top layer.  The perimeter of the Crystal filter is soldered to the bottom ground plane.  The top layer has a full perimeter shield fence and another shield fence separating the two sections.  Two "lids" are soldered to the top of the fences.  Various matching circuits, filtering, or attenuators can be added, using the available pads on the component side of the board.

Generic Schematic for PWB

     SKPWB-MCF rev A, Generic Schematic for PWB-MCF, in ExpressPCB software.
    No matter what monolithic filter you use, the characteristic impedance will not be exactly as the manufacturer claims.  Also, the input and output impedances may not be the same.  It will be close enough to give good results using standard inductors and capacitors.  If the builder would like to critically tune the filter, the impedance matching inductors and capacitors need to be variable or selectable.  The fixed input capacitors, X5 and  X6, could be decreased in value by 15 pfd and a small (2-20 pfd) variable placed in shunt with the fixed capacitors.  The inductors, X4 and X7, could be wound as toroids and be adjustable by removing or adding turns.  This critical tuning can improve the bandpass ripple by as much as 1 dB and decrease insertion loss by, perhaps, .5 dB.


SLIM-MCF-L024, 10.695 MHz, Monolithic Crystal Filter, size-A
   This module, using the 10L024, is a "blind" design, and is a place holder until I can find a good, inexpensive MCF that the home builder can easily acquire.

Schematic for SLIM-MCF-L024

     SKSLIM-MCF-L024, Schematic for SLIM-MCF-L024, in ExpressPCB software.
     PLSLIM-MCF-L024, Parts List in text format.
    The filter shown (XF) is distributed by U.S. Electronics.  However, their minimum quantity is 1000.  It has a center frequency of 10.695 MHz.  The bandwidth is 2.2 KHz and has a loss of -4.5 dB.   It has a 600 ohm inut/output impedance.
    This module, using the 10L024, is a "blind" design, and is a place holder until I can find a good, inexpensive MCF that the home builder can easily acquire.