sdrangel/plugins/channeltx/modam

AM modulator plugin

Introduction

This plugin can be used to generate a narrowband amplitude 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 continuously in 1 kHz steps from 1 to 40 kHz.

6: Modulation level

Adjusts the AM modulation level in %

7: 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.

8: 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

9: Input source control

9.1: Tone input select

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

9.2: Morse keyer input select

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

9.3: Tone frequency (kHz)

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

9.4: Audio input select

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

10: CW (Morse) text

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

11: Clear CW text

Clears the CW (Morse) text

12: Morse keyer controls

12.1: 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

12.2: Dots keying

Switch this button to send dots continuously

12.3: Dashes keying

Switch this button to send dashes continuously

12.4: Text keying

Switch this button to send the text typed into the text box (10)

12.5: 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

13: Audio file path

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

14: Audio file play controls

14.1: Audio file select

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

14.2: Audio file loop

Audio replay file at the end

14.3: 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.

15: Play file current position

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

16: Play file length

This is the audio file play length in time units

17: 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 14.3)