PL Tone Info
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Tone Squelch (uses
PL tones):
A squelch system
(used in wireless equipment) whereby the transmitter emits a tone at an
inaudible frequency. The receiver, upon detecting any signal checks to see if
that tone is present. If so, it allows the main signal to be heard, otherwise
it stays muted.
Thanks to:
http://www.webref.org/acoustics/t/tone_squelch.htm
CTCSS stands for
Continuous Tone Coded Squelch System, it is
the generic abbreviation and is used to minimize co-channel
interference.
Below is
the terminology used by different commercial companies for CTCSS:
PL is the Motorola Abbreviation for "Private Line".
QC is the RCA abbreviation for "Quiet Channel".
CG is the General Electric abbreviation for "Channel Guard".
CTCSS is
often referred to as a "PL" tone by many users.
Many repeaters require the use of a PL tone to access the repeater.
The frequency that a user transmits to access a repeater is the Repeater CTCSS
Encode Frequency.
The frequency that the repeater transmits to the user is the Repeater Decode
Frequency.
Deviation of a transmitted tone should be a maximum of 500Hz.
Contrary to
popular belief, the requirement of a PL tone to access a repeater does NOT mean
it is closed. A PL is frequently used to preclude interference in high RF
environments and lessen what is called kerchunking (unnecessary keying of the
repeater). Some repeaters may also generate a PL tone on the repeater
output so that repeater users who are equipped with a radio capable of decoding
PL will not hear other interference sources on the channel that would otherwise
open the squelch on the user's radio.
It is up to
the owner / trustee of the repeater to decide whether or not to make public the
PL tone for a particular repeater. MetroCor follows the wishes of the
owner / trustee in publishing the PL code only when so requested.
MetroCor
strongly recommends the use of PL on repeaters' receivers. PL is a minor
inconvenience when you consider how many potential problems it can
eliminate. The use of PL may be required for a coordination to be granted
if conditions so warrant, such as proximity to a co-channel repeater, or in an
area where band openings frequently aggravate co-channel interference problems.
MetroCor
hopes that repeater owners / trustees in a given area will standardize on a
particular PL tone and incorporate it into their operational plans. The
reason for this is to make it easier for users to operate the local repeaters
in an area, as some older radios are only capable of a single PL tone as
compared to modern radios which can have PL tones selected on a per-channel
basis.
Today most
radios have encode PL devices. Some radios have both, encode and
decode. If anyone needs a PL board for their radios they can check with
the radio manufacturer and see if the tone boards are available. If they
are not there are third party companies that manufacture PL units that fit into
most models of radios. If you do not feel comfortable in installing a PL
in your radio ask someone at your local radio club or contact any 2-way radio
repair shop and they will be able to assist you.
The
following chart showing each PL tone's two-character alphanumeric designator
and the corresponding tone frequency in Hertz.
Code |
Tone Freq. |
|
Code |
Tone Freq. |
|
Code |
Tone Freq. |
XZ |
67.0 |
|
1B |
107.2 |
|
6A |
173.8 |
WZ |
69.3 |
|
2Z |
110.9 |
|
6B |
179.9 |
XA |
71.9 |
|
2A |
114.8 |
|
7Z |
186.2 |
WA |
74.4 |
|
2B |
118.8 |
|
7A |
192.8 |
XB |
77.0 |
|
3Z |
123.0 |
|
M1 |
203.5 |
WB |
79.7 |
|
3A |
127.3 |
|
8Z |
206.5 |
YZ |
82.5 |
|
3B |
131.8 |
|
M2 |
210.7 |
YA |
85.4 |
|
4Z |
136.5 |
|
M3 |
218.1 |
YB |
88.5 |
|
4A |
141.3 |
|
M4 |
225.7 |
ZZ |
91.5 |
|
4B |
146.2 |
|
9Z |
229.1 |
ZA |
94.8 |
|
5Z |
151.4 |
|
M5 |
233.6 |
ZB |
97.4 |
|
5A |
156.7 |
|
M6 |
241.8 |
1Z |
100.0 |
|
5B |
162.2 |
|
M7 |
250.3 |
1A |
103.5 |
|
6Z |
167.9 |
|
0Z |
254.1 |
Thanks
to:
http://www.qsl.net/metrocor/ctcss.htm
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