¶ Generating and Observing a Basic FR3 Sine Wave
Transmit a single-tone sine IF at 1.5 GHz from a USRP-2974 through a Pi-Radio FR3 front-end up-converting to ~10 GHz over the air, then down-convert on the receive side and verify the tone with an ASCII DFT spectrum viewer.
¶ Overview
This tutorial exercises the Pi-Radio FR3 (Frequency Range 3) millimeter-wave front-ends available in COSMOS Sandbox 1. A USRP-2974 (Krypton — embedded X310, 10 MHz–6 GHz, 160 MHz BW) generates a 1.5 GHz IF carrying a 5 MHz baseband sine. A Pi-Radio front-end up-converts that IF to an FR3 carrier (~10 GHz) and transmits it over the air. A second Pi-Radio front-end receives the signal and down-converts it back to 1.5 GHz, where a second USRP-2974 running rx_ascii_art_dft confirms the tone.
The Pi-Radio web UI (running on the rfdev-* nodes at port 5006) is used to configure the LO frequencies for both front-ends.
This is a minimal "hello-world" experiment for the FR3 chain: no GNU Radio flowgraph, no additional signal processing — just a tone through the hardware.
¶ Learning outcomes
After completing this tutorial you will be able to:
- Configure Pi-Radio FR3 front-ends via the web UI (Low LO / High LO frequency settings).
- Transmit a tone with
tx_waveformson a USRP-2974 using the RIO0 PCIe path. - Observe a received tone with
rx_ascii_art_dfton a second USRP-2974. - Verify an end-to-end FR3 over-the-air link.
¶ At a glance
| Difficulty | Intermediate |
| Estimated time | 45 min |
| Domain / sandbox | sb1.cosmos-lab.org (FR3 Pi-Radio nodes) |
| Topic group | FR3 |
| Last verified | Not re-tested (migrated 2026-06-20) |
¶ Prerequisites
Background knowledge
- Familiarity with the USRP-2974 (Krypton) and its embedded X310 radio accessed via
resource=RIO0. - Basic RF concepts (carrier, IF, LO, up/down conversion).
- The six-step experiment life cycle.
Account & access
- A COSMOS account — register here.
- An approved reservation on sb1.cosmos-lab.org with the FR3 Pi-Radio nodes — see Make a reservation.
- SSH access to the console — see SSH access.
- Browser access to the Pi-Radio web UI on the
rfdev-*nodes at port 5006 (reachable through the console or a tunnel).
¶ Resources required
Devices / nodes
| Resource | Role | Qty | Notes |
|---|---|---|---|
| sdr1-piradio | Transmit host (USRP-2974) | 1 | Embedded X310; radio accessed as resource=RIO0 |
| sdr2-piradio | Receive host (USRP-2974) | 1 | Embedded X310; radio accessed as resource=RIO0 |
| rfdev-sdr1-piradio | Transmit Pi-Radio FR3 front-end | 1 | Web UI on port 5006; provides up-conversion to FR3 carrier |
| rfdev-sdr2-piradio | Receive Pi-Radio FR3 front-end | 1 | Web UI on port 5006; provides down-conversion from FR3 carrier |
Disk images
| Image | Load onto | Provides |
|---|---|---|
| fr3-tutorials.ndz | sdr1-piradio, sdr2-piradio | UHD with RIO0 support; FR3 tutorial tools preinstalled |
Software components
| Component | Version | Source |
|---|---|---|
| UHD (USRP Hardware Driver) | TODO: verify | preinstalled in fr3-tutorials.ndz |
| tx_waveforms | TODO: verify | preinstalled in fr3-tutorials.ndz |
| rx_ascii_art_dft | TODO: verify | preinstalled in fr3-tutorials.ndz |
| Pi-Radio web UI | TODO: verify | running on rfdev-* nodes at port 5006 |
Spectrum / RF / special
- 2× Vivaldi antennas (Tx and Rx) connected to the Pi-Radio front-ends. See the FR3 hardware pages for antenna layout.
- The example uses a ~10 GHz RF carrier (FR3 band). Stay within your reservation's allowed spectrum.
- TX gain: 30 dB on sdr1-piradio; RX gain: 30 dB on sdr2-piradio; all other Pi-Radio UI gains set to 0.
¶ Topology
Two USRP-2974 hosts (sdr1-piradio and sdr2-piradio) each connected to a Pi-Radio FR3 front-end (rfdev-sdr1-piradio and rfdev-sdr2-piradio) via RF cables. The front-ends transmit and receive over the air using Vivaldi antennas.
sdr1-piradio→rfdev-sdr1-piradio(Pi-Radio Tx FE) → antenna → air- air → antenna →
rfdev-sdr2-piradio(Pi-Radio Rx FE) →sdr2-piradio
Both Pi-Radio front-ends are configured via their web UIs (port 5006) to use Low LO = 1.5 GHz and High LO = 10 GHz.
¶ Setup
- Reserve the FR3 Pi-Radio resources in sb1.cosmos-lab.org and log into the console:
ssh <username>@console.sb1.cosmos-lab.org - Turn off all resources before imaging:
omf tell -a offh -t sdr1-piradio,sdr2-piradio,rfdev-sdr1-piradio,rfdev-sdr2-piradio - Load the FR3 tutorials image onto the USRP hosts:
omf load -i fr3-tutorials.ndz -t sdr1-piradio,sdr2-piradio - Turn the nodes on and confirm they are up:
omf tell -a on -t sdr1-piradio,sdr2-piradio,rfdev-sdr1-piradio,rfdev-sdr2-piradio omf stat -t sdr1-piradio,sdr2-piradio,rfdev-sdr1-piradio,rfdev-sdr2-piradio
See FR3 Setup for additional hardware-specific setup steps (included by the original tutorial via
[[Include(/UserGuide/FR3Setup)]]).
¶ Instructions
¶ Step 1 — Configure the Pi-Radio front-ends via the web UI
Open a browser and navigate to the Pi-Radio web UI for each front-end:
- Transmit front-end:
http://rfdev-sdr1-piradio:5006 - Receive front-end:
http://rfdev-sdr2-piradio:5006
On both front-ends, go to the Frequency panel and set:
- Low LO Frequency (GHz):
1.500000 - High LO Frequency (GHz):
10.000000
This pairs a 1.5 GHz IF with a 10 GHz high-side LO (and a 1.5 GHz low-side LO) to place the RF tone at ~10 GHz on the transmit side, and back to 1.5 GHz on the receive side. The exact placement depends on mixer sign/paths.
Leave Filters, Gain (except where noted below), and LO Suppression at defaults for this first run.
Set the following gains in the Pi-Radio UI:
- TX Gain: 30 (on the rfdev-sdr1-piradio / Tx front-end)
- RX Gain: 30 (on the rfdev-sdr2-piradio / Rx front-end)
- All other gains: 0
¶ Step 2 — Transmit a sine wave from sdr1-piradio
Open an SSH session to the transmitter node from the console:
ssh root@sdr1-piradio
Start tx_waveforms with a 5 MHz baseband sine on a 1.5 GHz IF, 10 Msps, amplitude 0.7, TX gain 30 dB:
tx_waveforms --args "resource=RIO0" --subdev A:0 --freq 1.5e9 --ampl 0.7 --gain 30 --wave-type SINE --ant TX/RX --rate 10e6 --wave-freq 5e6
Leave this running in the background (or open a second terminal to the transmitter).
¶ Step 3 — Observe the received tone on sdr2-piradio
Open an SSH session to the receiver node from the console:
ssh root@sdr2-piradio
Start the ASCII DFT spectrum viewer tuned to the 1.5 GHz IF at 20 Msps:
rx_ascii_art_dft --args "resource=RIO0" --subdev A:0 --freq 1.5e9 --ant RX2 --rate 20e6
You should observe a stable, narrow spectral line near the configured 5 MHz offset (side-markers set by the viewer) in the DFT display.
¶ Verification
- The Pi-Radio web UIs on both
rfdev-sdr1-piradioandrfdev-sdr2-piradioshow Low LO = 1.5 GHz and High LO = 10 GHz applied. tx_waveformsonsdr1-piradiostreams without errors.rx_ascii_art_dftonsdr2-piradioshows a stable, narrow spectral line near the 5 MHz offset within the 1.5 GHz IF band.- Stopping
tx_waveforms(Ctrl-C) causes the spectral line to collapse to the noise floor.
¶ Cleanup
Stop the UHD programs on both nodes with Ctrl-C, then power down all resources:
omf tell -a offh -t sdr1-piradio,sdr2-piradio,rfdev-sdr1-piradio,rfdev-sdr2-piradio
(No omf save needed unless you customized the image.)
¶ Troubleshooting
| Symptom | Likely cause | Fix |
|---|---|---|
tx_waveforms / rx_ascii_art_dft cannot find RIO0 |
USRP-2974 PCIe path not initialized | Reboot the host node; confirm with uhd_find_devices --args "resource=RIO0" |
| No spectral line visible in ASCII DFT | Pi-Radio LO frequencies not applied, or gain mismatch | Verify web UI settings on both rfdev nodes; confirm TX gain=30 on Tx FE and RX gain=30 on Rx FE, all others=0 |
| ASCII DFT shows noise/distortion only | Vivaldi antenna alignment or cable issue | Check antenna connections and orientation per the FR3 hardware page |
| Cannot reach rfdev web UI at port 5006 | Node not powered on, or network path not set up | Confirm omf stat shows rfdev nodes up; check console routing |
¶ References
- Pi-Radio website
- FR3 Setup guide
- Available SDR / USRP hardware
- Six-step experiment life cycle
- OMF commands reference
Author(s): COSMOS team · Last verified: Not re-tested (migrated 2026-06-20) · Tested image/release: fr3-tutorials.ndz · Tags: fr3, pi-radio, usrp, sdr, sine, millimeter-wave