Tune and select a mode

Tune a signal, select its mode, then adjust the passband until the wanted audio is clear.

Capture, view, and receiver frequency

Three frequencies have different jobs:

Frequency	Purpose
Receiver VFO	Selects the signal that you hear and demodulate.
SDR capture center	Selects the span of IQ samples delivered by the source.
Displayed view center	Selects the middle of the spectrum and waterfall display.

With a live SDR, tuning or panning can move the capture center automatically. Radio Bench keeps the receive passband visible and fits the capture around the view. The source frequency limits still apply.

For example, a 768 kHz capture centered at 14.200 MHz includes a USB signal at 14.250 MHz. A small VFO move can stay within that capture. Moving the view toward its edge can cause a hardware retune even if the VFO stays fixed.

An IQ file cannot supply frequencies outside its recorded span. With known center metadata, Radio Bench constrains tuning and the view to that span.

KiwiSDR can supply a wider remote spectrum than its listening IQ stream. Browsing that display does not move the IQ capture. Selecting a signal outside the listening capture can retune it. See KiwiSDR.

Tune a signal

Select a signal in the spectrum or waterfall. Drag the VFO marker for a continuous change.

Select a digit in the frequency display, then type the new value. Each digit tunes the receiver immediately and moves the selection to the next digit. Use the left and right arrow keys to move between digits. Press Escape to end entry.

Select a receiver mode

Choose AM, USB, LSB, CW, FM, or an available digital mode. Select the mode that matches the transmitted signal.

USB and FSK place the passband above the carrier. LSB places it below the carrier. RADE V1 uses lower sideband below 10 MHz and upper sideband at 10 MHz and above.

Read FM reception status

Start reception, select FM in RADIO, and open the FM group.

Detected tone shows the received CTCSS tone, such as 88.5 Hz. Detected code shows the received DCS code, such as D023. A dash means no detection is available.

Both readings describe the received signal in every squelch mode. They can differ from the tone or code selected in the controls.

Squelch state	Meaning
Open	The FM squelch gate allows audio through. RX mute, volume, and output routing still apply.
Closed	The FM squelch gate blocks audio under the selected squelch rule.
Waiting	Reception is running, but an FM status reading is not yet available.
Stopped	Reception is stopped. The tone and code readings clear.

Choose Squelch mode for the signal:

Noise: lower Squelch to admit weaker signals. Raise it to reject more noise.
CTCSS: select the required CTCSS tone and compare it with Detected tone.
DCS: select the required DCS code and compare it with Detected code.

In CTCSS or DCS mode, Off in the tone or code selector accepts any detected tone or code of that type. It still requires detection. Select Noise to receive without a tone or code requirement.

If squelch remains closed, check tuning, passband, and the selected squelch rule. A detected tone or code can be present while the selected rule blocks audio.

Stopping reception clears the readings. Starting again waits for fresh FM samples. Selecting another receiver mode hides the FM controls.

Set the passband

Adjust the low-cut and high-cut controls around the wanted audio. A narrow passband rejects nearby signals but can reduce intelligibility.

Start with a normal width for the selected mode. Narrow it only when interference makes that necessary.

Use tuning offsets

Open Settings > Tuning > TRANSVERTER OFFSET for converter or transverter offsets. Set Offset to Preset and select a Converter preset, or set it to Manual and enter a Manual offset (MHz).

The hardware center equals the displayed capture center plus the offset. For example, the NooElec Ham-It-Up (+125 MHz) preset adds 125 MHz. A displayed capture center of 7.100 MHz requests 132.100 MHz from the SDR. The VFO continues to show the received HF frequency.

Use an offset only with the corresponding converter. Radio Bench rejects a hardware center outside the selected source limits. Known-center IQ playback ignores the converter offset.

Set tuning preferences

Open Settings > Tuning.

Control	Starting point	When to change it
Automatic sideband	On	In SSB, crossing 10 MHz selects LSB below or USB above. Turn it off to retain your chosen sideband across that boundary.
Filter roll-off	Sharp	Use Sharp to reject nearby energy. Try Soft when a gentler receive-filter edge sounds better.
Snap to grid	Off, with a 100 Hz step stored	Enable it to align spectrum clicks and VFO drags to a grid. Choose 10–5000 Hz. Exact frequency entry remains available.

Stop IQ recording before retuning. Its tuning lock also prevents ordinary RF pan and zoom changes.

FT8/FT4 tuning

In the FSK workspace, select the protocol and band in the FSK workspace. The band supplies a dial preset. With CAT tracking enabled, the FSK profile controls the rig frequency.

Waterfall RX and TX markers select audio offsets, not the RF dial. Click for RX, Shift-click for TX, or drag a marker. Hold TX retains the chosen transmit offset when starting a reply.