Motorola MICOR High Band to 222 MHz Conversion
LOW PASS FILTER
Modification Courtesy of SEITS
Original Concept and Images by David A. Cooley N5XMT

This modification changes the cutoff frequency of the harmonic lowpass filter from 190 MHz to approximately 230 MHz.

Step 1: Remove the filter from the main casting by removing 4 screws.

Step 2: Remove the cover to the harmonic filter by removing the 2 screws on the rear of the unit.

Step 3: Remove 1 turn from the center of each coil, and solder the 2 ends back together. Stretch the coils to their original length and fine tune length for minimum VSWR. (See Fig. 7)

Step 4: Re-assemble and re-install filter assembly in Radio.

The Radio should make 25-30 watts output and the power control board should work exactly as it did with the original PA.



Here's an overview schematic of a completed LPF. Click on it for a larger view.

 

Page recreated by: Kevin K. Custer W3KKC
Original Concept Copyright 1997 David A. Cooley N5XMT
Copyright 1998 SEITS, N5XMT, and W3KKC.

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