Motorola in the early years of PL the highest PL frequency was 186.2. This was due to older tube circuits and not being able to filter out the PL "hum" very well.
--- In [email protected], Mike Morris WA6ILQ <wa6...@...> wrote: > From the draft article: > > >The overall system is designed around a specific set of low frequency > >tones ranging from about 65 Hz to about 250 Hz. The oldest list that I > >am aware of (from November 1952) is ten tones: 100.0 cps, 110.9 cps, > >123.0 cps, 136.5 cps, 151.4 cps, 167.9 cps, 186.2 cps, 206.5 cps, > >229.1 cps and 254.1 cps, identical to tones 1Z through 0Z in the > >Motorola standard tone list. Over the years the list has been expanded - by > >1965 Motorola was using 26 tones from 82.5 to 192.8 Hz, and by 1983 > >the MSF5000 station offered 42 tones in it's list. These days, and > >depending on which industry "standard" set you chose to use, there > >are 32, 37, 38, 41, 42, 47 or 50 tones available, and the U. S. > >Military has their own unique tone of 150.0 Hz that doesn't appear on > >any list of standard Land Mobile tones. >
