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mirror of https://github.com/f4exb/sdrangel.git synced 2024-12-19 08:05:49 -05:00
sdrangel/plugins/channelrx/demodnfm
2017-01-30 23:28:06 +01:00
..
CMakeLists.txt Channel plugins: Removed useless link dependency on QT OpenGL and Multimedia 2016-10-27 08:46:06 +02:00
demodnfm.pro Windows build: set SSE options for all demodulator plugins 2016-11-07 18:57:52 +01:00
nfmdemod.cpp NFM demod: new discriminator 2017-01-30 23:28:06 +01:00
nfmdemod.h NFM and DSD plugins: use double for base type of moving average. There was an overflow with float on high power signals (over ~5 dBm) preventing the squelch to close back 2017-01-15 17:03:32 +01:00
nfmdemodgui.cpp NFM and DSD demods: corrected squelch open GUI display 2017-01-17 00:49:52 +01:00
nfmdemodgui.h AM and NFM demods: improve signal meter with 50ms refresh rate 2016-12-06 01:57:35 +01:00
nfmdemodgui.ui Signal meter: adjust font 2016-12-07 02:53:10 +01:00
nfmplugin.cpp NFM demod: new discriminator 2017-01-30 23:28:06 +01:00
nfmplugin.h Tx ph.1: plugins (2) 2016-10-13 23:42:08 +02:00
readme.md AM, NFM and SSB demods: corrections to the readme 2016-12-08 07:58:14 +01:00

NFM demodulator plugin

Introduction

This plugin can be used to listen to a narrowband FM modulated signal. "Narrowband" means that the bandwidth can vary from 5 to 40 kHz.

Interface

NFM Demodulator plugin GUI

1: Frequency shift from center frequency of reception direction

The "+/-" button on the left side of the dial toggles between positive and negative shift.

2: Frequency shift from center frequency of reception value

Use the wheels to adjust the frequency shift in Hz from the center frequency of reception. Left click on a digit sets the cursor position at this digit. Right click on a digit sets all digits on the right to zero. This effectively floors value at the digit position.

3: Channel power

Average total power in dB relative to a +/- 1.0 amplitude signal received in the pass band.

4: Level meter in dB

  • top bar (green): average value
  • bottom bar (blue green): instantaneous peak value
  • tip vertical bar (bright green): peak hold value

5: RF bandwidth

This is the bandwidth in kHz of the channel signal before demodulation. It can be set in steps as 5, 6.25, 8.33, 10, 12.5, 15, 20, 25 and 40 kHz.

6: AF bandwidth

This is the bandwidth of the audio signal in kHz (i.e. after demodulation). It can be set in continuous kHz steps from 1 to 20 kHz.

7: Volume

This is the volume of the audio signal from 0.0 (mute) to 10.0 (maximum). It can be varied continuously in 0.1 steps using the dial button.

8: Squelch threshold

This is the squelch threshold in dB. The average total power received in the signal bandwidth before demodulation is compared to this value and the squelch input is open above this value. It can be varied continuously in 0.1 dB steps from 0.0 to -100.0 dB using the dial button.

9: Squelch gate

This is the squelch gate in milliseconds. The squelch input must be open for this amount of time before the squelch actually opens. This prevents the opening of the squelch by parasitic transients. It can be varied continuously in 10ms steps from 10 to 500ms using the dial button.

10: CTCSS on/off

Use the checkbox to toggle CTCSS activation. When activated it will look for a tone squelch in the demodulated signal and display its frequency (see 10).

11: CTCSS tone

This is the tone squelch in Hz. It can be selected using the toolbox among the usual CTCSS values and -- for none. When a value is given and the CTCSS is activated the squelch will open only for signals with this tone squelch.

12: CTCSS tone value

This is the value of the tone squelch received when the CTCSS is activated. It displays -- if the CTCSS system is de-activated.

13: Audio mute

Use this button to toggle audio mute for this channel. The button will light up in green if the squelch is open. This helps identifying which channels are active in a multi-channel configuration.