N4JRI's Radio Pages:  Stupid Scannergeed Tricks

Find CTCSS Tones by Ear!

Shock your friends not only with this truly rare skill,

but with this record deep dive into geekdom!

The Necessity that Mothered this Invention:  Finding a CTCSS is a sluggish process if you have to program a lot of guesses, or your scanner uses CTCSS search. Yours truly, the ever-unique N4JRI, had an early interest in PL tones due to massive QRM in an urban environment, and the seeking of specific users on shared frequencies.

The Basic Idea:  As a professional musician, I am skilled in identifying musical notes which--what a coincidence--are audio tones! By comparing the CTCSS tone to a known reference pitch (A at 440 Hz is preferred) I can identify a CTCSS tone with pretty fair accuracy. Using my method, it should not be necessary to program in more than five tones, and often you'll get it on the first try.

Gory Details:  CTCSS tones run in frequency from 67.0-251.3 Hz. The note known as 'Middle C' is approximately 261.6 Hz, with the C an octave below around 130.8, and the C two octaves below at 65.4. If you know the frequencies of the various musical notes, you can compare them directly with notes from a cheap electronic keyboard. The only special skill that I have is that of determining the tone by comparing it to an A-440 reference pitch.

Results of Experiment: Confirmed geekhood, even among the scanner crowd. This ability was actually tested at a meeting of Capitol Hill Monitors. Got it on my first try, BTW. Ask Alan Henney. After gaining this highly valuable skill, one of the first thing I heard was the telltale key-up tone of a shared repeater using DCS. After all this, I still had to tap my discriminator output and hook up a DC-440 to my rig.

 

Table of Frequencies for Musical Notes

in CTCSS Frequency Range

Note Audio Frequencies
C 65.4, 130.8, 261.6
C#/Db 69.3, 138.6
D 73.4, 146.8
D#/Eb 77.8, 155.5
E 82.4, 164.8
F 87.3, 174.6
F#/Gb 92.5, 185.0
G 98.0, 196.0
G#/Ab 103.8, 207.7
A 110, 220
A#/Bb 116.5, 233.1
B 123.5, 246.9

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