⚠ A minimum of 48 kS/s I/Q sample rate in the baseband is required in 2400A mode for the coder/modulator to work correctly. Other modes only require 8 kS/s however such a low rate is not recommended and at least 48 kS/s should be used anyway.
<h3>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 arrows. Pressing shift simultaneously moves digit by 5 and pressing control moves it by 2.
<h3>2: Channel power</h3>
Average total power in dB relative to a +/- 1.0 amplitude signal generated in the pass band.
<h3>3: FreeDV mode</h3>
Use this combo box to select which FreeDV standard is used. The following are supported:
-`2400A`: FSK-4 wideband (6 kHz) modulation with 1300 b/s compressed voice to be used at 29 MHz and above similarly to FM analog usage. [Details here](https://www.rowetel.com/?p=5119)
Effective only in binaural mode: reverses left and right audio channels so that the left is connected to Q and the right to the I complex signal channel.
Check to select input audio to be displayed on the VU meter (6)
<h3>5: Volume</h3>
This is the volume of the modulating audio signal from 0.0 (mute) to 2.0 (maximum). It can be varied continuously in 0.1 steps using the dial button. The Loudspeaker button is the audio mute toggle.
<h3>6: Level meter in %</h3>
Use the checkbox (4) to select between input audio and modulator output display
- top bar (beige): average value
- bottom bar (brown): instantaneous peak value
- tip vertical bar (bright red): peak hold value
You should aim at keeping the peak value below 100% using the volume control
<h3>7: Input source control</h3>
<h4>7.1: Tone input select</h4>
Switches to the tone input. You must switch it off to make other inputs available. Note that tone input has been kept from other modulators but does not make much sense for digital voice modes.
<h4>7.2: Morse keyer input select</h4>
Switches to the Morse keyer input. You must switch it off to make other inputs available. Note that the Morse keyer has been kept from other modulators but does not make much sense for digital voice modes.
<h4>7.3: Tone frequency (kHz)</h4>
Adjusts the tone frequency from 0.1 to 2.5 kHz in 0.01 kHz steps.
<h4>7.4: Audio input select and select audio input device</h4>
Left click to switch to the audio input. You must switch it off to make other inputs available.
Right click to select audio input device. See [audio management documentation](../../../sdrgui/audio.md) for details.
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
⚠ WARNING: what follows is not really useful if you do not use a proper Morse keyer with direct audio feedback. There is a significant audio delay either with the direct monitoring or by monitoring the transmitted signal so keying with this audio as feedback is not practical
This disables text or continuous dots or dashes. Toggle input from keyboard or mouse (see 16b.3). Occasionally the focus may get lost and you will have to deactivate and reactivate it to recover the key bindings.
When keyboard and mouse control is activated move the pointer to this area to use the left button as the dot paddle and the right button as the dash paddle. In straight mode both buttons have the same effect (key down).
Click on the button and while selected type a character or character and modifier (Shift + key for example) to select which key is used for dots. The key or key sequence appears next (here dot `.`)
Click on the button and while selected type a character or character and modifier (Shift + key for example) to select which key is used for dashes. The key or key sequence appears next (here dot `.`)
Toggle play/pause file play. When paused the slider below (20) can be used to randomly set the position in the file when re-starting.
<h3>13: Play file current position</h3>
This is the current audio file play position in time units relative to the start
<h3>14: Play file length</h3>
This is the audio file play length in time units
<h3>15: Play file position slider</h3>
This slider can be used to randomly set the current position in the file when file play is in pause state (button 17.3)
<h3>16: Spectrum display frequency span</h3>
The transmitted signal is further decimated by a power of two before being applied to the channel spectrum display and used to set the in channel filter limits. This effectively sets the total available bandwidth depending on the decimation:
- 1 (no decimation): 24 kHz (2400A) or 4 kHz (other modes)
