User Guide

RimuSDR User Guide

A practical guide to using RimuSDR and RimuDAX — from connecting to your first radio through configuring audio and the integrated CWX keyer. For CAT control, see the RimuCAT Guide.

Radio Connection Panadapter Controls

RimuSDR · RimuDAX · CWX · FlexRadio 6000 · 8000 · Aurora

What This Guide Covers

This guide covers the core workflows in the RimuSDR suite. For installation, see the Installation Guide.

RimuSDR

The primary SDR operating interface for connecting to your radio and controlling the panadapter.

Radio discovery and connection
Local and SmartLink (remote) radios
Panadapter and waterfall controls
Slice management and audio settings
Sub-band privilege visualization

RimuDAX

Routes processed audio and raw I/Q streams between the radio and Linux audio applications.

TX, Mic, and RX channel management
Virtual PulseAudio device naming
Multiple simultaneous DAX channels
I/Q streams for SDR analysis tools

CWX Keyer

Integrated CW keyer for sending text directly from RimuSDR without external hardware.

Integrated CWX memory keyer
Adjustable keyer speed (WPM)
Memory slots for stored text
Instant abort/stop control

Radio Discovery and Connection

The RimuSDR connection UI was designed with hams in mind who have more than one radio on the local network or who operate through multiple SmartLink accounts. Whether you have two radios on your bench or access to club and personal radios over SmartLink, the connection workflow is intended to make switching between them straightforward without credential juggling.

Local Radio Discovery

RimuSDR discovers FlexRadio 6000, 8000, and Aurora series radios on the local network automatically — no IP address entry required. Use File › Connect LAN Radio to open the local radio browser, then select the radio you want to connect to from the list. The computer running RimuSDR must be on the same subnet as the radio — for example, if the radio has an IP address of 192.168.0.10, the machine running RimuSDR must have an address in the 192.168.0.* range.

File menu showing the Connect LAN Radio option — Use **File › Connect LAN Radio** to open the local radio browser. The option is available whenever RimuSDR is not already connected to a radio.

Local radio selection list showing discovered radios on the network — RimuSDR lists all FlexRadio radios found on the local network. Select the radio you want to connect to and click Connect. If a radio does not appear, confirm it is powered on and reachable on the same network segment.

SmartLink Connection

SmartLink lets you connect to a FlexRadio over the internet through FlexRadio's cloud service. RimuSDR can store multiple sets of SmartLink credentials, so operators with access to radios under different accounts — such as a personal radio and a club radio — can switch between them without re-entering login details each time.

SmartLink Manager with multiple credential sets stored — Multiple SmartLink credential sets can be stored in RimuSDR. Add a set for each account you have access to — the SmartLink Manager will list the radios available under each set of credentials.

SmartLink Manager showing radio configuration details — The SmartLink Manager displays configuration details for radios registered in your FlexRadio SmartLink account, making it straightforward to verify connection settings and select the radio you want to use.

MultiFLEX shared operation

FlexRadio supports MultiFLEX, allowing multiple operators to connect to the same radio simultaneously. Each operator gets independent slices, panadapters, and DAX access. RimuSDR participates in MultiFLEX sessions automatically when the radio permits it.

Panadapter and Waterfall Controls

The panadapter displays the RF spectrum across the selected band. The waterfall below it shows signal history over time, making it easy to identify activity and spot signals.

Panadapter display

The panadapter shows real-time signal strength across the visible bandwidth. Use the band selector to switch bands or enter a frequency directly to jump to a specific spot. The reference level and display range can be adjusted to suit band conditions.

Waterfall

The waterfall display shows RF activity over time to help identify CW, digital, and SSB signals at a glance. Waterfall speed and color gradient can be adjusted to match your operating preferences and screen brightness.

Multiple panadapters

RimuSDR supports up to eight simultaneous panadapters (subject to radio capability). Each panadapter is independent and can be placed on a different band, making it easy to monitor multiple bands at once.

Slice receivers

Each panadapter can host one or more slice receivers. A slice defines the receive frequency, mode (USB, LSB, CW, AM, FM, etc.), filter width, and audio routing. Slices can be moved by clicking in the panadapter or by typing a frequency.

Tracking Notch Filters (TNFs)

TNFs can be placed anywhere in the panadapter to attenuate a specific interfering carrier or signal. Drag a TNF to reposition it or adjust its width to fit the interference. TNFs operate in the digital domain on the radio itself.

Spots

Spot data can be displayed on the panadapter, showing the callsign and frequency of spotted stations as overlays on the spectrum. This makes it quick to click on a spot and move the active slice to that frequency.

RimuSDR main operating view with panadapter and waterfall — RimuSDR main operating view. The panadapter shows the current band spectrum and the waterfall displays recent signal history below it.

RimuSDR with two simultaneous panadapters — Two panadapters displayed simultaneously, allowing the operator to monitor two different bands at once without switching views.

Sub-Band Privilege Visualization

A horizontal indicator below the panadapter frequency scale shows which license class segments are in view, providing at-a-glance confirmation that you are operating within your authorized sub-bands.

Color-coded sub-bands

Each license class (Technician, General, Amateur Extra, etc.) is assigned a distinct color that appears as a band below the frequency scale. As you pan or zoom the panadapter, the color bands update to reflect the privileges for the visible segment.

Customizable regions

RimuSDR ships with a US privileges file but the configuration is fully replaceable. Edit the file to match your region's band plan, define custom frequency ranges, specify license classes, and assign any colors you prefer. The file uses a straightforward text format.

Granular segment definition

Sub-band definitions can be as fine-grained as needed. Common practice in the US plan is to define separate segments for voice, CW, RTTY, and digital modes within each band. Any number of named segments can be defined at any frequency granularity.

Sub-band privilege color coding below the frequency scale — The colored band below the panadapter frequency scale represents sub-band privileges for the visible spectrum, giving immediate visual feedback on authorized operating segments.

Sub-band privilege configuration interface — The sub-band configuration interface where frequency ranges, license classes, and display colors are defined. The default US region file can be edited or replaced with a custom file for any region.

DAX Audio Configuration

RimuDAX creates virtual PulseAudio devices that route processed audio between the radio and Linux applications. Enable the channels you need and select the matching device names in your digital-mode software.

Connecting RimuDAX

Start RimuDAX after RimuSDR is connected and the DAX channel is active on the desired slice. RimuDAX will list the same station that RimuSDR is connected to. Select it and click Connect.

TX channel

The TX channel carries transmit audio from your Linux application to the radio. Enable TX before enabling any RX channel. The corresponding PulseAudio device is named flex.dax.tx — set this as the audio output in your digital-mode software.

Mic channel

The Mic channel routes microphone audio from Linux into the radio for voice operation over DAX. Enable Mic when you want to use a Linux audio input (headset, USB microphone) as the radio's transmit microphone source.

RX channels (RX1–RX8)

Each enabled RX channel corresponds to a DAX channel number set on a slice in RimuSDR. For example, if the slice has DAX channel 1 selected and the DAX button active, enable RX1 in RimuDAX. The PulseAudio device is named flex.dax1.rx1 — set this as the audio input in your digital-mode software.

Confirming audio flow

The RX channel level meters in RimuDAX should respond to signals received on the corresponding slice in RimuSDR. A silent meter when signals are present usually means the DAX button is not enabled on the slice, or the wrong DAX channel number is selected.

PulseAudio device names

All RimuDAX virtual devices appear in PulseAudio with the flex. prefix, making them easy to identify in system audio tools such as pavucontrol. You can verify connections and monitor levels in pavucontrol while RimuDAX is running.

RimuDAX audio routing interface — The RimuDAX interface showing TX, Mic, and RX channel controls. The level meters confirm audio is flowing between the radio and the Linux audio system.

RimuSDR audio device settings, where the system playback device for the SDR receiver audio can be selected independently of the DAX audio path.

DAX setup notes

Order mattersRimuSDR must be connected and the DAX button active on the slice before RimuDAX is started, otherwise RimuDAX will not see the audio stream.
DAX channel numbersThe DAX channel number selected on the slice in RimuSDR must match the RX channel enabled in RimuDAX. Slice DAX channel 1 maps to RX1, channel 2 to RX2, and so on.
Same stationRimuDAX must be connected to the same station (radio) as RimuSDR. In most home setups only one station will appear in the list.

CWX Keyer Operation

RimuSDR includes an integrated CWX keyer for sending CW text directly from the application without an external keyer or hardware interface.

Sending text

Type CW text into the CWX text field and press Enter or click Send. The text is queued and sent to the radio as CW at the current keyer speed. The radio handles all timing and spacing at the hardware level.

Keyer speed

The keyer speed (WPM) is displayed and can be adjusted while text is queued. Changes take effect at the next character boundary so the current character is always sent at the speed it was started at.

Memory slots

The CWX keyer provides memory slots for storing frequently sent text such as a CQ call, signal report, or contest exchange. Assign text to each memory slot and recall it with a single click during an operating session.

Abort sending

The Stop (abort) button clears the CWX transmit queue immediately and drops the radio out of transmit. Use Stop any time you need to interrupt a send in progress.

CWX notes

Mode requirementThe slice must be set to CW or CW-U mode before using CWX. Attempting to send CW while the slice is in a phone or digital mode will not produce the expected output.
Radio-side processingAll CW timing is processed by the FlexRadio hardware, not in software, producing clean sidetone and accurate timing at any speed.
SidetoneThe CW sidetone comes from the radio's audio output. Adjust sidetone level and pitch using the radio's profile or front-panel controls.

Related Guides

Step-by-step integration guides for connecting digital-mode applications to RimuSDR.

Installation Guide

Download and install RimuSDR, RimuDAX, and RimuCAT on Debian, Ubuntu, Raspberry Pi, or via AppImage, and activate your license.

RimuCAT Guide

Set up CAT control for logging, digital-mode, and automation software using TCP or virtual serial port connections.

WSJT-X Setup Guide

Configure WSJT-X for FT8, FT4, and related weak-signal digital modes using RimuDAX for audio and RimuCAT for CAT control.

Fldigi Setup Guide

Configure Fldigi for HF digital modes including PSK31, RTTY, and others using RimuDAX audio and a RimuCAT virtual serial port.