[amsat-bb] Re: 67 Hz PL Frequency Tolerance?

Félim Doyle M3HIM Felim.M3HIM@ntlworld.com
Wed Aug 23 01:21:44 PDT 2006

As a general principle what is considered a reasonable tolerance for CTCSS
(e.g. on repeaters)? As the next frequency up from 67Hz is 69.3Hz +/-2Hz
sounds very risky. I know not all transceivers support the 69.3Hz tone,
jumping straight from 67Hz to 71.9Hz instead but I believe that this is the
exception rather than the rule (even my older handhelds all support 69.3Hz).

A quick Google search for "PL Tone" yielded this definition on one repeater
site ...

"The system is designed around a set of relatively low frequency tones (32
or 38 depending on which "standard" you use) ranging from 67.0 Hz to 250.3
Hz. The tones are a perfect sine wave and the frequency tolerance is very
tight, typically +/- 0.5 Hz. The tone is encoded and injected into the
transmitter after the audio shaping circuits. The frequency deviation
(level) is typically 0.4 to 0.8 kHz which is rather insignificant when
compared to the typical 5 kHz voice deviation."

73 de

Félim M3HIM
Aylesbury, Buckinghamshire, UK
----- Original Message ----- 
From: "Bill Ress" <bill@hsmicrowave.com>
To: <amsat-bb@amsat.org>
Sent: Tuesday, August 22, 2006 7:59 PM
Subject: [amsat-bb] 67 Hz PL Frequency Tolerance?

> I've looked through the AMSAT web site and the AO-51 book but can't any
> information about the frequency tolerance of the satellite receive
> system to the 67 Hz PL tone.
> I believe someone way back when actually did some measurements after it
> was launched but I can't find it either. Does +/- 2 Hz sound right? What
> about the level (deviation) require? Is it the same for the Mode V and L
> receivers?
> Regards and thanks...Bill - N6GHz
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