sdrangel/plugins/channeltx/modnfm

NFM modulator plugin

Introduction

This plugin can be used to generate a narrowband frequency modulated signal. "Narrowband" means that the bandwidth can vary from 1 to 40 kHz.

Interface

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 generated in the pass band.

4: Channel mute

Use this button to toggle mute for this channel.

5: RF bandwidth

This is the bandwidth in kHz of the channel signal filtered after modulation. It can be set in discrete values: 3, 4, 5, 6.25, 8.33, 10, 12.5, 15, 20, 25 and 40 kHz

6: Audio frequency bandwidth

This is the bandwidth in khz of the modulating signal filtered before modulation. It can be set in kHz steps from 1 to 20 kHz

7: Frequency deviation

Adjusts the frequency deviation in 0.1 kHz steps from 0 to 25 kHz

8: Volume

This is the volume of the audio signal from 0.0 (mute) to 2.0 (maximum). It can be varied continuously in 0.1 steps using the dial button.

9: Level meter in %

• top bar (beige): average value
• bottom bar (brown): instantaneous peak value
• tip vertical bar (bright red): peak hold value

You should aim at keepimg the peak value below 100% using the volume control

10: Input source control

10.1: Tone input select

Switches to the tone input. You must switch it off to make other inputs available.

10.2: Morse keyer input select

Switches to the Morse keyer input. You must switch it off to make other inputs available.

10.3: Tone frequency (kHz)

Adjusts the tone frequency from 0.1 to 2.5 kHz in 0.01 kHz steps

10.4: Audio input select

Switches to the audio input. You must switch it off to make other inputs available.

11: CTCSS switch

Checkbox to switch on the CTCSS sub-audio tone

12: CTSS tone frequency

Select the CTCSS sub-audio tone in Hz among these values: 67.0, 71.9, 74.4, 77.0, 79.7, 82.5, 85.4, 88.5, 91.5, 94.8, 97.4, 100.0, 103.5, 107.2, 110.9, 114.8, 118.8, 123.0, 127.3, 131.8, 136.5, 141.3, 146.2, 151.4, 156.7, 162.2, 167.9, 173.8, 179.9, 186.2, 192.8 and 203.5 Hz

14: CW (Morse) text

Enter the text to be keyed when Morse input is active and in text mode

15: Clear CW text

Clears the CW (Morse) text

16: Morse keyer controls

16.1: CW keying speed

Sets the CW speed in Words Per Minute (WPM). This is based on the word "PARIS" sent 5 times. For 5 WPM the dot length is 240 ms. In other terms the dot length is calculated as 1.2 / WPM seconds. The dot length is used as the base to compute other timings:

• Element (dot or dash) silence separator: 1 dot length
• Dash: 3 dot lengths
• Character silence separator: 3 dot lengths
• Word silence separator: 7 dot lengths

16.2: Dots keying

Switch this button to send dots continuously

16.3: Dashes keying

Switch this button to send dashes continuously

16.4: Text keying

Switch this button to send the text typed into the text box (14)

16.5: Text auto repeat

Switch this button to auto repeat the text keying

12.6: Text play/stop

Use this button to stop sending text. When resuming keying restarts at the start of text

17: Audio file path

The path to the selected audio file to be played or dots if unselected

18: Audio file play controls

18.1: Audio file select

Opens a file dialog to select the audio file to be played. It must be mono 48 kHz 16LE raw format.

18.2: Audio file loop

Audio replay file at the end

18.3: Play/pause file play

Toggle play/pause file play. When paused the slider below (17) can be used to randomly set the position in the file when re-starting.

19: Play file current position

This is the current audio file play position in time units relative to the start

20: Play file length

This is the audio file play length in time units

21: Play file position slider

This slider can be used to randomly set the currennt position in the file when file play is in pause state (button 18.3)