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Masters Communications
5 Pole CTCSS Filter Board
For Two-Way Radio Applications

Model PLF-15


Actual Size Assembled PLF-15 Filter.
(Click image to enlarge)

Schematic Image.
(Click image to download a PDF copy)

Overview:
The PLF-15 is a 5 pole active filter using two op-amp sections. A genuine high-performance TI op-amp is used to make a filter to remove CTCSS tones from an audio path. The design cut-off frequency is 350 Hz, and provides a sharp reduction of these frequencies. The attenuation is sufficient to remove tone signaling in repeater systems so CTCSS can be regenerated without the effects of the lingering presence of the original tone.

The PLF-15 has a knee set at 350 Hz.  The supplied op-amp is a high-performance TL062, and when run from 10V or more has excellent dynamic range and low noise.  The IC is socketed in case the builder chooses to use some other op-amp they consider superior, or easy replacement if it should ever fail.

This filter was optimized by Robert Meister WA1MIK.  Bob reworked the part values for the best performance.  The CTCSS filter was designed to give a good compromise between maximum rejection of CTCSS tones below 186.2 Hz and minimizing the voice roll-off below 400 Hz.  Many thanks go to Bob for his time and effort to help bring you these quality filters.  Be sure to check out his evaluation article.
FL10 Evaluation

Assembly:
If you purchased our kit, refer to the parts list and make sure you have all of the components you need to build it.
Click here for Parts List.
Assembly can be done by personal choice, but you may find it easier to install the resistors first, followed by the capacitors, jumper(s), IC socket, and header socket.

The resistor color bands can be difficult to see without good lighting and strong magnification.  If in doubt, use an ohmmeter and double check the value before soldering resistor components in place.  Please refer to the additional notes about component identification in the parts list.

Refer to the board silkscreen for connection to the power supply and audio path..
GND = ground
O = output
I = input
+V = supply voltage

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Product of Kevin Custer - Masters Communications, all rights reserved.
Performance optimization of these filters by Robert Meister - WA1MIK.
Specifications may change without notice.
Images property of Kevin Custer - W3KKC