PL / CG (CTCSS) Filter Construction Index
The links below will allow you to build several working subaudible tone filters.
No warranty as to the quality or usefulness is expressed by Repeater Builder

A repeat audio board designed for the GE Master Exec II   from Micro Computer Concepts   171k JPG file   donated by Ron Wright N9EE
Note that the page is oriented for printing, not viewing.

A High Pass PL Tone Filter   By Bob Dengler NO6B

A High Pass PL Tone Filter   By Kevin Custer  W3KKC

The PL filter from a Motrac, we use it in a Micor   By Kevin Custer  W3KKC

GE's Mastr Exec II tone board   This board has the encoder, decoder and tone filter (from LBI30854 which replaced LBI4143).   Look for the section on the "Tone Reject Filter".

Mastr-Pro Aux Receiver chassis   This is LBI4172 which is for a rack-mount power supply chassis for the Mastr-Pro receivers.   One option was a line amplifier that came in tone and non-tone versions.   Look for the section that describes "Line Amplifier A503/A504".   A503 does not have the filter, A504 has it.   Jsut print those two schematic pages and compare them.

Mastr-Pro base station / repeater power supply chassis   This is LBI4423, and contains the 4EA24A12 / A13 line amplifier information: the A12 version is used in carrier squelch stations (non-tone), and the A13 is for stations with Channel Guard.   Simply compare the two schematics.

Another one of GE's tone filter boards   Just another look at how GE did it (from LBI30727, not sure which radio it's for).

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Page created 14-Sep-2004 by Kevin K Custer W3KKC
Page last updated 17-Aug-2005 by WA6ILQ (added N9EE's donation)

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