Tune and receive

This chapter follows a receive session from selecting a slice to tuning, filtering and managing interference. Frequency, mode, filter and receive DSP changes apply to the slice you control. A slice you only listen to has restricted controls; its Your volume and mute remain personal to this device.

Figure 3. Mode (1), tuning step (2), filter display and presets (3), AGC/AUTO controls (4), and receive/transmit offsets (5). The illustrated values are the captured station's settings.

Start with the right slice and route

1. Connect and wait for fresh spectrum data. Select the desired VFO flag, or its letter tab in the RX applet when several slices are present.
2. Read the slice letter, frequency and ownership line. Take control if necessary before changing its receive settings.
3. Open the flag's speaker tab. Select SPEAKERS or PHONES for the intended output, unmute it and set a comfortable AF level. Those output names use the devices selected in Setup > Audio > Devices.
4. Check mode, filter and offsets before evaluating a signal. A leftover RIT offset or an inappropriate filter can make a correctly entered VFO frequency sound wrong.

With multiple receivers, audio from more than one slice can be mixed into your output. Temporarily mute the others when diagnosing the selected receiver, then restore the mix. Do not change several receivers' DSP settings merely because the combined audio is difficult to understand.

Tune by frequency, signal position or step

For a known frequency, double-click the flag's frequency display, enter an explicit value such as 7.260 MHz or 7260 kHz, and press Enter. Confirm the displayed readback. Leaving the entry without submitting it returns to the frequency display. Use explicit units when moving between MHz and kHz to avoid an unintended interpretation.

For an unknown signal, click its position in the spectrum or waterfall. A short click tunes the active slice to the nearest selected tuning step. Dragging empty space pans the view; dragging inside the selected passband slides the VFO. The gesture table in the window chapter shows which parts of the display change tuning, filters or presentation.

For small corrections, use the wheel over the VFO frequency field or over an empty area of the band. The RX applet's STEP arrows move through the available step choices and wrap at the ends. The step button in the flag's X/RIT page cycles choices too. Choose a small step for fine alignment and a larger step for band exploration. The step controls the increment and click rounding; it does not change the receive filter width.

If a change is refused, check the lock icon and ownership text. Unlock a slice you control, or request Take control for one you only hear. Check the Core's message when the requested frequency requires moving a shared receive window. Changing a local display is not proof that the Core accepted a radio retune: use the final frequency and received audio as confirmation.

Change bands and inspect the recalled state

Use Band > HF and choose the named band, or select GEN for general coverage or WWV from the Band menu. Selecting a band restores that band's saved frequency, mode and filter for the operating path; a first visit uses its initial state. WWV is not a promise that every click lands on a fixed 10 MHz frequency. Read the recalled VFO, mode and filter before tuning further.

Check the antenna and hardware filter readbacks when changing bands because the physical station can have different per-band routing. A band choice does not extend the connected radio's frequency range or add a transverter. The separate VHF/transverter and Band Stacking surfaces are not implemented in the covered build.

Use View > Band Plan to select a shown plan and its label size, from Off through Huge. Check the highlighted segment and frequency scale. A band-plan label is operating context; it does not choose your receive mode or grant TX permission. Keep it legible without obscuring the passband.

Select the mode before the filter

Choose the mode in the RX applet, or open the flag's mode tab and select it there. The current mode name is shown on the flag and changes the preset bank.

A mode label describes how the slice demodulates. It does not by itself select the transmitter, establish a software audio route or connect a reporting service. Check those separately when using digital modes.

Choose and adjust the receive passband

1. Select a filter preset in the RX applet or flag's mode/filter page. The buttons show their widths, and their tooltip identifies the preset and low/high edges. Confirm the shaded passband and width readback.
2. Listen before narrowing it. Reduce the width when an adjacent signal is the problem; widen it again if the wanted signal loses useful content.
3. For a custom edge, drag the shaded passband edge in the spectrum, or use the RX applet's passband display. Check both edges after the change.
4. To reuse a shape, right-click a preset and choose Edit this preset…. Enter Name, Low and High, inspect Width, then Save. Cancel leaves the saved entry unchanged. Reset this preset restores that slot; the editor also provides Reset to Default.

Filter values are relative to the slice's tuned frequency. A lower-sideband filter therefore uses a different placement from an upper-sideband one even when both buttons show the same bandwidth. Check the actual edges, not only the width. A narrower filter excludes more of the spectrum; it cannot make an interfering signal inside the wanted passband disappear without also removing some wanted audio.

The preset bank belongs to the Core. Editing a preset can affect other operators who later select it. Setup > DSP > Filter Presets provides the larger editor with mode selection, names/edges, ordering and reset operations. Choose the required mode and slot before editing; the covered editor does not provide RADE rows in its ordinary WDSP preset list.

Shift-click on a receive preset is a special operation: it applies the RX preset and requests a one-time copy of that passband to the transmit audio filter. It does not establish continuous RX/TX tracking. TX settings permission is still required; an RX change can succeed while the TX copy is refused. Read TX BW afterwards if matching was your intention. Use an ordinary click for receive-only filter selection.

Set receive volume and AGC deliberately

AF and AGC-T solve different problems. If audio is simply too loud, adjust AF or output volume. If background noise is being raised between signals, review AGC mode and AGC-T while holding AF steady. Changing AF alone cannot repair an overloaded radio input.

The AGC choices in the flag/RX applet are Off, Long, Slow, Med and Fast. Off uses a fixed gain controlled with AGC-T. Longer recovery keeps gain from rising as quickly between parts of a signal; faster recovery follows more rapid changes. Select one, listen across several signal changes, then compare with the previous choice. The best choice depends on the signal and conditions; this manual does not treat a captured setting as a universal preset. Use AUTO when you want noise-floor-based adjustment, and check its indication before making a manual AGC-T change.

Set squelch without losing weak signals

Open the flag's speaker tab or the RX applet, enable SQL, and adjust its threshold while listening to a clear gap between signals. Stop when the unwanted background closes, then tune a wanted signal and confirm it opens the audio again. If a weak signal disappears, reduce the threshold or turn SQL off before trying stronger noise reduction. Squelch silences the output; it does not remove an interferer from the passband.

The threshold uses the selected mode's scale: SSB uses a normalized threshold, AM a dB scale, and FM a linear threshold. Recheck it after a mode change rather than copying a number between unlike scales. In a no-audio diagnosis, turn SQL off temporarily so that a closed gate cannot be confused with the wrong output device. Tone squelch and FM repeater controls are not implemented in this build.

Use input attenuation and preamp controls

The RX applet's input controls can affect the ADC feeding several slices, which makes them different from per-slice AF and AGC. The label may read ATT, S-ATT or A-ATT, depending on stepped and automatic attenuation state. The available range and preamp choices come from the connected radio. A slice using the other ADC can have that ADC's own settings.

If an ADC-overload indication appears, first identify the affected input and current antenna/preamp/attenuation state. Increase available attenuation or reduce unnecessary preamp gain while watching the overload indication and wanted signal. If overload clears, compare reception before continuing. Coordinate such input changes with operators sharing that ADC. Turning down AF hides loud audio but leaves the radio input condition unchanged.

In a remote window these controls show and request the Core's input state. Read the disabled control's reason if the Core does not offer it. Do not assume the range or antenna/preamp arrangement of one HPSDR model applies to another. Hardware setup and antenna routing are covered separately.

Select noise treatment by the problem

Open the flag's DSP tab. The NR bank selects one noise-reduction method; NB/NB2, SNB and the automatic notch are separate controls.

Start with the other treatments off and the receiver correctly tuned. Turn on one treatment, compare speech or wanted tones with it on/off, and keep it only if intelligibility improves. Excessive treatment can remove wanted detail or introduce artifacts. Right-click a method for its frequently adjusted parameters; More Settings… leads to its detailed DSP page where offered. Receiver DSP setup explains those parameters and their dependencies.

DFNR, MNR and NNR availability is reported by the controlling Core/build. A disabled button's tooltip gives the reason; reconnecting repeatedly is not an installation method for a missing processor or model. If a noise algorithm makes audio timing worse, compare with it off and capture the processor/link status before changing unrelated network or device settings.

Remove a persistent tone with a manual notch

1. Tune and identify the unwanted tone in the passband. Right-click its frequency in an empty part of the spectrum and choose Add notch here. Check the frequency shown in the popup before applying it.
2. Confirm a notch marker appears. Enable TNF through the DSP menu or the status-bar TNF control if the master notch processing is off.
3. Drag the notch centre to align it, or drag an edge to change width. The wheel over a selected notch adjusts its width; Shift gives finer adjustment. Listen to the result rather than relying only on the marker.
4. Right-click the marker to choose Width, Bypass Notch / Activate Notch, or Remove Notch. Widths below the filter's achievable minimum are disabled and explain their minimum.

A notch is a frequency/width filter entry, not a new receive slice. Making it wider can remove wanted audio too. The TNF master affects all notches, whereas bypassing one entry leaves the other entries available. Setup > DSP > TNF provides the notch-management page for inspecting the bank and its DSP settings. The notch menu does not provide a permanent/temporary persistence choice in this build.

Use RIT, XIT and CTUN for different jobs

RIT offsets received frequency without replacing the main VFO setting. Enable it in X/RIT or the RX applet, adjust its signed Hz value and listen. The 0 button clears its stored offset. Disabling RIT bypasses the offset; check both enable state and value when returning to ordinary operation.

XIT offsets the transmitted frequency. It is not a receive correction. Check it before every TX session, especially after listening to a signal that needed RIT. The XIT offset is a slice setting; editing it does not itself grant transmit ownership or key the radio. For a larger split, using a separate TX slice can make the two operating frequencies clearer.

CTUN concerns the receiver window and band view. Right-click empty spectrum and enable CTUN (independent pan) under Tuning to keep the receive window fixed while tuning within it. The VFO moves while the pan stays put. Turn it off to return to a view following the VFO. The checkbox can be unavailable when the Core does not provide remote C-Tune support. None of these three controls is a substitute for selecting the intended transmit slice.

Worked example: improve a weak voice signal

Start on a slice you control, with its output audible and no unexpected RIT/XIT. Enter the known frequency, select the correct sideband, and choose a filter that includes the wanted voice. Hold AF steady while choosing AGC mode and setting AGC-T. If a nearby signal is entering at one edge, narrow that edge before trying noise reduction. For steady background noise, compare one NR method with Off. For distinct impulses, compare NB and NB2. For a single persistent tone, compare ANF or a narrow manual notch.

Finish by reading the frequency, mode, width, offsets and active DSP buttons. Restore treatments that failed the listening comparison to Off. If intelligibility is still poor, capture the signal/overload and output-route observations before following the troubleshooting chapter. This gives the next check a specific symptom instead of an unexplained collection of changed settings.