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 transmission/h3>

Use the wheels to adjust the frequency shift in Hz from the center frequency of transmission. 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. Wheels are moved with the mousewheel while pointing at the wheel or by selecting the wheel with the left mouse click and using the keyboard arroews. Pressing shift simultanoeusly moves digit by 5 and pressing control moves it by 2.

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)