Before you begin: Have a simple receive plan and identify the required driver, antenna input, power and audio.
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New to the terms? Open the quick explanations.
- SDR
- Software-defined radio: hardware and software perform radio functions together. An external receive-only SDR supplies another receiving path.
- Panadapter
- A spectrum and waterfall view around a frequency. The display and the receiver that supplies it are separate ideas.
- RF
- Radio-frequency signals carried by antennas and RF connections. Transmitted RF can damage an unprotected receive input.
- CAT
- Computer-assisted transceiver control, such as supported tuning and mode commands. CAT is separate from the digital-mode audio path.
- PTT
- Push-to-talk or transmit keying control. In this station, a compatible keying output commands the receiver-protection hardware.
- Sampled bandwidth
- The range of RF captured by the active receiver configuration at one time. More software windows do not extend that range.
- SNR
- Signal-to-noise ratio: the signal’s level in relation to the noise. Consistent measurement conditions matter when comparing readings.
- IQ recording
- A recording of received sample data that supported software can process later, within the recorded range.
Include Receiver Protection from the Start
1. Understand the Build and Its Protection
Plan protection with the first receive path. For a station that can transmit: receive feed → suitable PTT-controlled SDR protection → SDR receiver → USB → PC / SDR Console → audio.
Separate control path: radio TX/PTT output → protection hardware PTT input. Provide the hardware’s specified power and verify all relevant transmit bands and exposed receiver inputs before transmitting. Use the correct shared-antenna or separate receive-feed arrangement.
You may perform a controlled listening-only checkout with local transmitters disabled, but that temporary state is not a completed transmit-capable station. Install and identify the SDR →
2. Choose One Receiver: Examples Used at W3UJ
These four receivers are used at W3UJ. You only need one receiver to complete a basic receive system. The RSPdx-R2 is the example used below, not a required purchase.
SDRplay RSPdx-R2
The receiver used in this guide’s basic build. Follow its antenna selection, USB connection, and SDR Console setup.
Station reference →
SDRplay RSPduo
Another receiver used at W3UJ. Follow its model-specific connections and software setup.
Station reference →
RX-888 MKII
Used with SDR Console at W3UJ. Its device-specific driver and USB setup differ from the SDRplay installation.
Station reference →
Nooelec NESDR SMArt v5
Used primarily for VHF/UHF reception at W3UJ. Follow the Nooelec setup instructions and use the appropriate driver.
Station reference →For this build, we use the SDRplay RSPdx-R2. Follow one receiver through the complete setup—from protected RF and PTT connections through USB and software setup to your first signals in SDR Console. Other receivers require their own drivers and device settings. Find the appropriate receiver driver →
3. Gather the Parts and Plan Protection
First get one independent SDR receiving a known signal, with the transmitter off. You can learn the receiver and SDR Console before integrating the transmit radio.
| Needed for the First Receive Checkout | What It Does |
|---|---|
| One SDR supported by the installed SDR Console version | Supplies the receive sample data. |
| A computer, suitable USB connection, and required device support | Runs SDR Console and communicates with that receiver. |
| Suitable receive antenna, feedline, and adapters | Provide a known, traceable receive feed. |
| The required power arrangement | Powers the receiver and supporting equipment according to their specifications. |
| Working audio output | Lets you confirm reception by listening. |
| PTT-controlled RF protection, compatible keying connection, and required switch power | Required for a transmit-capable station: protects the exposed SDR receive path during local transmission. Select hardware appropriate to the actual RF arrangement, band and power; verify it before transmitting. |
Can wait: CAT synchronization, extra monitors, another SDR, splitters, a second radio, and a portable case. Receiver protection is required before the setup is exposed to unsafe transmitted RF, whether antennas are shared or separate.
Use Windows setup and the software directory to identify the device and install the appropriate support.
4. Identify the Connections on the Example Receiver
The walkthrough uses the RSPdx-R2. If you chose another receiver, use its manufacturer’s connector and driver instructions; the protected RF, USB/data, and audio paths serve the same separate purposes.
One Receiver. Choose One Input
The RSPdx-R2 connects to your computer by USB. SDR Console provides the tuning controls, audio, spectrum, and waterfall.
- ANT A / ANT B
- SMA antenna connectors.
- ANT C
- BNC antenna connector.
Select the input that matches your connected antenna in SDR Console. These are selectable inputs on one receiver, not three independent tuners. Only one antenna input is selected at a time. ANT A and ANT B cover the receiver’s full specified frequency range; ANT C covers 1 kHz–200 MHz. These labels identify hardware inputs, not dedicated antenna types.
Where ANT C fits: the first listening exercise uses ANT A; the basic integrated example uses ANT B. The W3UJ separate receive-antenna expansion uses all three connectors for selectable feeds: the shared receive-loop splitter feeds ANT A, and the customized receive switch feeds ANT B and ANT C. That is an optional expansion, not three antennas you need for a first build. SDRplay hardware specifications ↗
5. Trace the Protected Receive Path
This teaching example uses hardware documented at W3UJ. The listening checkout is performed with transmission disabled, not a claim that a particular current software build has been bench-tested with this exact arrangement. Software versions and completed test records must be filled in for your installation.
| Part | Example and Job |
|---|---|
| Receiver | SDRplay RSPdx-R2, one receiver connected to the computer. |
| Computer | Compatible Windows PC. W3UJ uses Windows 11; verify support for your processor, software, and device drivers. |
| USB and power | Suitable USB data connection and the manufacturer-specified power arrangement. |
| Antenna input | A suitable receive feed, through the appropriate protection hardware for a transmit-capable station, connected to ANT A (SMA) for this example. Select the input actually connected; use adapters appropriate to the equipment. |
| Software | SDR Console plus the compatible SDRplay API/support package. Use official compatibility and download instructions. |
| Audio | Computer speakers or headphones, with the intended output selected. |
| Receiver protection | Include suitable PTT-controlled RF protection, the compatible radio keying connection, and switch power before any local transmitting is enabled. |
| Deferred | CAT synchronization, virtual COM ports, splitters, LNA, additional monitors, and transmitter integration. |
Receive path: antenna/feedline → suitable PTT-controlled RF protection → RSPdx-R2 ANT A → USB → Windows PC → SDR Console → audio output. This is a functional overview; use the linked model-specific protection wiring instructions. Keep local transmitters off during the first checkout and address any exposure to nearby transmitted RF.
Install and discover: follow the single installation procedure. Return here for the listening checkout and record the actual versions and settings in the workbook.
Reference status: exact installed SDR Console/API versions, model-specific gain settings, and controlled test results are not supplied here. Do not treat an undocumented value as a default for every receiver.
Official references: RSPdx-R2 hardware · SDRplay API · SDR Console downloads and RSPdx-R2 support. Open the bench workbook →
6. Connect, Configure, and Confirm Reception
Keep the transmitter off throughout this first receive checkout. An unprotected receiver must not be exposed to unsafe transmitted RF, including RF coupled from nearby antennas.
- Establish the protection plan. Identify shared or separate receive RF routing, compatible PTT output, protection hardware, and required switch power. Keep local transmission disabled throughout this listening test; verify protection before enabling any transmitter.
- Choose something you can check. Prefer a strong signal you can already hear on another receiver. A local AM broadcast station may be useful if it is within the SDR’s coverage. Record the actual frequency and mode; do not assume a particular amateur band has activity.
- Confirm Windows sees the receiver. Follow the PC setup guide and the receiver manufacturer’s driver/API instructions in Software & Drivers.
- Select the receiver and connected antenna input. Start with one device and one known receive feed.
- Enter the frequency and choose the mode. Use AM for an AM broadcast signal, or the appropriate mode for the signal you chose.
- Listen. Check the computer’s audio output, volume, and receive filter. A visible trace alone is not the success criterion.
- Write down the working setup. Record the receiver, antenna input, frequency, mode, software, and audio output before changing anything.
Success: the receiver is recognized, the intended antenna is selected, and you can hear the chosen signal clearly enough to identify it. If you cannot, use troubleshooting to identify whether recognition, reception, or audio is failing before adding CAT control or transmit integration.
Listening success is not transmit clearance. Before enabling the radio or WSJT-X to transmit, complete and verify PTT-controlled receiver protection. Keep transmission disabled until that check is complete.
Later Integration and Original Build Notes
Optional detail retained for the later stage or a return visit. Follow the main path above for the current task.
7. Integrate the Transceiver and Verify Protection
Once your independent SDR checkout works, the next build can keep your familiar transceiver available for receiving and transmitting while adding a separate SDR receiver. This is the basic integrated arrangement introduced in the October 21 QRZ master. It is an optional next stage, not a replacement for the first receive-only checkout above.
The example uses a Yaesu transceiver, an SDRSwitch.com RXin/RXout switch, one SDRplay RSPdx-R2, a compatible receive splitter, a computer and SDR Console. The drawing shows an FTDX10; the FT-991A requires its own documented antenna connection and transmit-control cable.
What Each Part Does
- Yaesu: retains its own receiver and transmitter.
- SDRSwitch.com RXin/RXout: provides the main antenna/transceiver path and the external receive loop, with model-specific transmit protection.
- Splitter in the receive loop: returns one receive branch to the transceiver and supplies the added SDR from the other branch. It distributes receive signals; it does not protect an SDR from transmitted RF.
- RSPdx-R2 and computer: provide the additional receive-only path, spectrum display, audio and software filtering.
Read the Receive Path in Two Branches
During receive, follow antenna → switch ANT → switch RX OUT → splitter common/input. One splitter output returns to switch RX IN → transceiver receiver; the other goes to RSPdx-R2 ANT B → USB → computer → SDR Console. This integrated example uses ANT B (SMA); the independent checkout above uses ANT A (SMA). Select whichever input is actually connected. ANT C is BNC.
“Optional splitter” in the source illustration describes a choice between switch configurations. This dual-receiver example includes the splitter so both receivers have a receive feed. Do not simply omit it and leave the receive loop on the SDRSwitch.com RXin/RXout switch open. Follow the switch manufacturer’s configuration for the intended operating mode.
Build and Check in Order
- Draw RF, PTT, USB/CAT and power as separate paths. Choose hardware for the actual band and power level.
- With transmit RF disabled, establish the main transceiver receive path and then the splitter/SDR receive branch.
- Select the connected RSPdx-R2 input and confirm reception with a known signal. Check the transceiver’s receiver separately, then both together.
- Establish and verify the correct PTT/control path, power requirements, protection state, switching timing and RF isolation before transmitting. A relay click or a no-RF PTT test alone does not establish safe RF isolation.
- Add optional CAT tracking only after both receivers work. Save the ports, software versions and checkout results in the workbook.
A splitter adds receive-path loss. Its specification depends on the actual design and frequency; the W3UJ resistive Mini-Circuits splitter should not be assumed to have the same loss as every two-way power divider. See the existing station-development splitter discussion and the LNA explanation before adding gain.
Follow the worked connection example → · RF and PTT protection → · Record the build →
Manufacturer reference: SDRSwitch.com RXin/RXout setup and dual-receive arrangements. Use the manufacturer’s documentation for the exact model, connector functions and protection requirements.
8. Add Optional CAT Tracking
After the RF routing and PTT protection have been verified, you may add optional CAT control. CAT allows the radio and computer to communicate, making it possible for the radio and SDR software to stay synchronized. A great early milestone is having the radio and SDR follow one another as you change frequency.
Before enabling any local transmission that can expose an SDR input, through a shared or separate antenna, install and verify the appropriate SDR Switch and its PTT/transmit-control connection. These are two different jobs: CAT lets the radio and computer talk to each other. PTT tells the SDR Switch that you are transmitting. The SDR Switch provides the switching and protection needed for your SDR receive equipment to safely coexist with your transmitter.
The exact PTT/transmit-control connection varies by radio. Depending on the equipment, you may encounter connections labeled PTT, TX GND, SEND, ACC, LINEAR, TUNER, DATA, or REMOTE. Always check the documentation for your particular radio and SDR Switch rather than assuming that a cable or connector that physically fits is electrically correct.
Verify the protection action before transmitting. Before transmitting into a newly assembled SDR system, confirm that the PTT/control connection actually causes the SDR Switch to change to its transmit/protection state. Do not assume that a correctly fitting cable means the protection system is operating correctly.
Reference Build and Test Record
For: an operator setting up one RSPdx-R2 on a Windows PC, with SDR Console as the receiving application.
First outcome: identify the receiver, select its connected antenna input, tune a known signal and hear usable audio. Start with the independent receive checkout; move to the shared-antenna dual-receiver build after that works.
Have ready: the receiver, compatible PC and USB data cable, suitable receive feed and adapters, supported SDRplay API and SDR Console installation, and headphones or speakers. A transmit-capable station also requires the appropriate protection switch, documented PTT/control cable and switch power from the start. A shared-antenna SDRSwitch.com RXin/RXout arrangement additionally needs its model-specific RF routing and, for the dual-receiver example, the receive splitter.
Independent receiver parts and path → · Shared-antenna integration → · Build workbook →
Record the configuration you actually tested
Before calling your build complete, record the receiver model and antenna input, PC/Windows details, SDR Console version, SDRplay API version, USB connection, chosen test signal, mode/filter and actual result in the workbook. For integration, also record the switch model, splitter ports, PTT connector and completed protection checks.
The equipment and connection examples are documented here. Exact installed software versions and a completed bench-test record for this reference build have not been supplied. The website cannot establish those facts remotely; mark them complete only after checking your installation.
Two examples, two recorded input choices: the independent first checkout uses ANT A; the later shared receive-loop example uses ANT B. These are different configurations. Select the input actually wired in your build; the letters do not prescribe a universal antenna assignment.
One Continuous Example: FT-991A and One External SDR
Read the Supporting Reference
Use the FT-991A as the operating radio and one external receiver, such as the RSPdx-R2 documented at W3UJ, as the learning example.
- Decide: identify the capability you want beyond the radio’s existing display.
- Protect: plan and connect suitable SDR protection, its PTT keying path, and required power. Leave transmission disabled until protection is verified.
- Receive: leave the transmitter off, identify the SDR in Windows and SDR Console, select the connected antenna input, and tune a known signal.
- Learn: practice mode, filtering, gain, span, and waterfall settings.
- Integrate: use the detailed build and protection references to establish RF routing and PTT protection for your actual hardware.
- Operate: add supported CAT synchronization if wanted, confirm the actual radio frequency, and use the operating workflow.
This is a teaching route using the documented equipment. Use the source diagrams and model-specific instructions for the physical wiring; the sequence is not a substitute for protection verification.
Learn to Follow the Paths
Read the Supporting Reference
Don’t look at an SDR station as one complicated system. Follow one path at a time. Understanding what each path does makes both troubleshooting and future expansion much easier.
RF = where the radio signal travels • CAT = where frequency and control information travels • PTT = how the protection system knows you are transmitting • USB = how equipment communicates with the computer • POWER = what makes each active component operate
W3UJ SDR Build Zone
Read the Supporting Reference
Planning, connections, and verification
Your First SDR Build — Getting Started
Read the Supporting Reference
Still choosing an approach? Return to the Yes/No decision tree before selecting equipment.
If you followed the earlier decision tree and chose to integrate an SDR with your transceiver, you can start here. If you’ve looked at the W3UJ station diagrams and thought, “This looks complicated,” remember that you’re looking at the end result of a station that evolved over time. My station didn’t start this way.
My SDR journey began with a Yaesu FT-991A, an SDR, an SDR Switch, and a computer. I started with a basic idea, got it working, learned from it, and then added capabilities as my interests grew. You can do exactly the same thing.
One Radio + One SDR + One SDR Switch + One Computer
Your First Goal: Get One SDR Receiving
Read the Supporting Reference
Don’t make your first goal building the complete W3UJ station. Connect the SDR to your computer, install the required drivers and SDR software, and learn the basics. I use SDR Console, but regardless of the software you choose, start by learning how to tune, change modes, adjust bandwidth and gain, use filters, and understand the spectrum and waterfall displays.
Once you can see a signal, tune to it, hear it, and understand what you’re looking at, you’ve taken the most important first step.
Build and Test One Step at a Time
Read the Supporting Reference
Plan and connect the SDR Switch, its compatible PTT control, and required power as part of the station build. Keep transmit RF disabled while getting one SDR receiving. Verify protection before enabling transmission. Add optional CAT tracking after the RF and protection paths are understood. Change one thing at a time and test it before moving on. The station diagrams show where my SDR station eventually went; they are not a shopping list or a requirement for getting started.
Plan Your Simple Build
Read the Supporting Reference
Even a basic SDR station deserves a plan. It doesn’t have to be an engineering drawing. A piece of paper with a few boxes and lines is enough. Start with the radio, SDR Switch, SDR, and computer, and then ask how CAT will connect, how the radio will provide PTT/transmit control, whether the SDR Switch uses an RX OUT/RX IN loop that requires a splitter, whether you plan to stay with HF or may eventually want VHF/UHF, and whether your computer has the connections and USB capability your SDR requires.
You don’t have to build for every possibility. You simply want to understand how the pieces of your first system will connect before you start connecting or purchasing them.
As you work through these steps, refer to the station configuration diagrams. They provide a visual reference for how the radio, SDR Switch, splitters, SDR receivers, computer, antennas, and control connections fit together. Don’t worry about understanding every connection at first. Start by following one signal path at a time.
➜ You know where to start. Now let’s plan how your station will go together. ➜
Original QRZ Topic Graphic
Read the Supporting Reference
The original QRZ illustration is preserved here for reference. Use the explanations and current setup steps in this guide for context.
Historical Single-Radio Integration Diagram
View the Single-Radio At-a-Glance and Detailed Connections
This diagram belongs to the later transceiver-integration stage. It is not the parts list or wiring required for the independent receive checkout above.
At-a-Glance View ↓ · Detailed Connection View ↓
Single-Radio At-A-Glance View
Historical FT-991A integration diagram. A first receive-only setup does not require this full arrangement.
Single-Radio Detailed Connection View
Follow the same historical arrangement one function at a time: RF routing and receive distribution, direct PTT protection, USB/computer connections, then DC power and the LNA supply. Repeated equipment boxes refer to the same hardware. The LNA shown here was later removed from the station; this diagram is not the minimum parts list for your first receive setup.
Open the scalable single-radio connection map ↗ · Back to the At-a-Glance View ↑ · Compare the two-radio configuration →
Based on W3UJ station documentation. Station examples describe this installation; consult model-specific documentation for your equipment. Sources and editorial scope.