 Readme                                                                                 9th July 2022
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=  CTCSSDecoder - SDR# plug-in                                                                      =
=                                   by Vasili (TSSDR) and updated and modified by thewraith         =
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Description
===========
Decode the CTCSS tone transmitted with a NFM signal and display.

Can display CTCSS tone on plug-in panel, frequency spectrum or in a auxiliary (aux) window.
From v1.3.2.0+, will send CTCSS tone value to Frequency Scanner plug-in (v2.2.12.0+) to be
 displayed/logged with in that plug-in.

Set audio only to be heard if matched a set CTCSS tone. (Tone squelch)
NOTE: You cannot use the CTCSS and DCS tone/code squelch at same time.


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Installation
============
 see MagicLine.txt


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Usage
=====
Start SDR# and start the radio (press press button).
Select detector to be 'NFM'.
Open/Find the 'CTCSS Decoder' panel and enable the 'Detect' check-box.
Tune VFO to any active frequency to determine if singal has a CTCSS tone.
On receiving CTCSS tone, "Tone Detected" and CTCSS tone will be displayed.

Labels and controls
===================
Displayed CTCSS tone
- Small text: Real detected tone value
- Large text: CTCSS tone (that matches standards values)
  Double clicking this label will open the configure window

"Set this tone"
- Sets the current displayed CTCSS tone to be used for tone squelch.
  This will enable the code 'Squelch' at same time.

"Squelch" and "Tone"
- When enabled, will only allow audio to be heard if received CTCSS tone matches the set CTCSS tone.
- NOTE: You cannot use the CTCSS and DCS tone/code squelch at same time.

"Show on spectrum"
- Shows CTCSS tone at VFO marker
- Shows CTCSS tone in bottom left corner offrequency spectrum

"Aux window"
- Opens an auxiliary window which is a mirror of plug-in panel minus some options
- Remembers last window position.

"No reset"
- By default, when frequency is changed the displayed CTCSS tone will be cleared.
- When enabled, will prevent CTCSS tone from been cleared until next tone is detected.
  e.g. This my be desirable when using with Frequency Scanner plug-in.


Configure window (open by double clicking the large bold CTCSS value label)
================
Spectrum label Y offset [100]
- Positions the VFO marker CTCSS value at a % of available space in spectrum

Keep Aux window open
- When enabled, will force the Aux window to be alway open
  Default is to close window when not playing or not NFM.


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Other information

Info on CTCSS
- ETSI TS 103 236 V1.1.1 - 4.1 CTCSS - Table 1: Table 1: CTCSS Code Frequencies on page 8
  NOTE: This is not the extended list of CTCSS tones used.
  NOTE: Not all CTCSS tones are used by this plug-in [55 defined]
        39 standard + 16 non standard (some Kenwood and Military)
        Kenwood tones (used ones are when same as standard tones or when are not conflicting with standard tones)
        - NOTE: Conflicting tones are too close to a standard tones to distuish correctly.

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 Notes, bugs, limits or other things of possible interest
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NOTE:
 Not all aspects of this plug-in, whether it be it's usage, features, options, bugs, issues, problems 
 or any other unforeseeable things maybe covered by this documentation.


Theme colors may not be perfectly matched.

Increasing SDR# Audio latency may improve CTCSS decoding [60+ mS]
- Only for v1.3.2.0 and less.

Off frequency transmissions may affect CTCSS decoding.

Lower (+decimated) samplerates do not yield good enough resolution to accurately calculate CTCSS tone values
- Tones that are closer together may not be detected correctly

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This modified version and documentation by thewraith2008 started in 2020

see Changelog.txt for more details about changes and fixes.

Support forum here:
 https://forums.radioreference.com/forums/software-defined-radio.193/

Release thread here:
 https://forums.radioreference.com/threads/fixing-the-sdr-ctcss-plug-in.431010/

NOTE: Support is not guaranteed. Especially if the answers are contained in the documentation or on forum.




Special thanks to the creators of the following software:

 SDRSharp (SDR#) by Youssef Touil (Airspy)
  https://airspy.com/
  The CTCSS Decoder plug-in utilises code from the SDR# plug-in API.
   As such, that code used by the plug-in is the property of Youssef Touil (Airspy).

 CTCSS Decoder (this original SDR# Plug-in) by Vasili (TSSDR)
  http://rtl-sdr.ru
  Thanks Vasili for allowing me to update this plug-in.




 Necessary Disclaimer:
  This program is "as is"
  This program most probably contains errors, bugs or whatever and that it may crash itself, SDR#, the plug-ins,
   windows or your car. You accept that you use it at your own risk.
  I make no promises to update it or support it.
  I'm under no obligation to implement anything.
  The creator of SDR# has the right to change their code as they see fit. Because of this, this program/plugin 
   can and probably will break.
  Not reading the read-me/set-up and usage documentation files may cause you issues.
