Welcome to Radio Waves Weekly — Issue #013! TX9W went on the air from the Marquesas this weekend — pile-ups are open and 15m conditions are co-operating. Yesterday, April 18, marked World Amateur Radio Day, observed every year on the anniversary of the IARU’s founding in Paris. The Pebble HF is the most talked-about QRP kit of the spring. BrowSDR turns any browser into a full SDR receiver. A homebrew FRI-Match tuner, a proven four-band half-loop, and a live DX-cluster display on a ₹800 ESP32 board round out this week’s ten.
1. TX9W — Marquesas Islands (IOTA OC-027) On the Air Until April 30
DX ALERT
Six operators from the Oklahoma DX Association and France are QRV from Hiva Oa on 160–6m — CW, SSB, FT8, FT4, RTTY — emphasis on CW and SSB. Daily ClubLog uploads; LoTW after return. For VU stations, 15m afternoon grey-line and early 20m openings are productive.
DXpedition website → k5we.com/tx9w/
2. World Amateur Radio Day — April 18, Theme: “Advancing the Spirit Through Innovation”
EVENT
IARU’s annual celebration commemorates the Union’s founding in Paris in 1925. This year’s theme spotlights innovation — from FT2 to satellite and emergency comms. IARU member societies worldwide ran special events and on-air activations throughout April 18 UTC.
IARU WARD page → iaru.org/on-the-air/world-amateur-radio-day/
3. Pebble HF — A Sub-$50 QRP Kit with a Built-In Key and Mic
QRP KIT
Introduced March 22 by Ham Radio Duo (N4BKY/N4FFF) with firmware by Guido PE1NNZ. Hardware derived from Barb WB2CBA’s design. Built-in straight key, microphone, one-watt output — the lightest possible field kit. Early-backer group-buy underway; target retail $50.
QRPer first look → qrper.com/2026/03/pebble-hf-an-ultra-affordable-qrp-radio-kit-with-big-potential/
4. QRP Labs QMX — Detailed Build Review by Dave Richards AA7EE
KIT BUILD
AA7EE’s thorough April 2026 write-up covers assembly of the five-band 3–5W multimode transceiver — USB-C audio/CAT, embedded SDR receiver, CW/FT8/WSPR beacon. Honest notes on assembly density, sidetone quirks, and on-air performance on 20m CW and FT8.
Full review → aa7ee.wordpress.com/2026/04/07/the-qrp-labs-qmx-transceiver/
5. BrowSDR — Turn Your HackRF or RTL-SDR V4 Into a Browser-Based Remote SDR
SDR PROJECT
Released April 14. Connects via WebUSB — no drivers needed. Rust/WASM DSP, unlimited simultaneous VFOs, WFM/NFM/AM/SSB/CW, Whisper AI transcription, and WebRTC remote sharing from anywhere. Open source, AGPL-3.0. Live demo at browsdr.jlynx.net.
Write-up → rtl-sdr.com/browsdr-turn-your-hackrf-or-rtl-sdr-into-a-browser-based-remote-websdr/
6. Half Loop Antenna for 80, 40, 20 and 15 Metres — UR0GT Design
ANTENNA BUILD
Multiband half-loop fed at ground level — covers four HF bands without a complex matching network or tower. Mechanically stable and compact. UR0GT’s proven design with full dimensions, installation photographs, and construction notes.
Full guide → vu3dxr.in/half-loop-antenna-for-80-40-20-and-15-meter-ham-bands
7. Homebrew FRI-Match Antenna Tuner — Two Knobs, No Switches, 80–10m
CIRCUIT BUILD
VE2DPE builds PA0FRI’s modified Z-Match — an L-network far more efficient than the common T-network. Covers 80–10m with two variable capacitors and a tapped inductor. Full schematic, construction photos, winding details, and on-air test results included.
Build article → hamradiosecrets.com/homebrew-antenna-tuner.html
8. Propagation News — SFI Climbing, Geomagnetic Disturbance Settling, Tropo Building
PROPAGATION
NOAA forecasts SFI reaching 145 by April 23 as the coronal-hole disturbance fades. High pressure establishing across western Europe signals sustained tropo lift. Good 15m and 20m windows for TX9W from South Asia. International Marconi Day on April 25.
Full bulletin → norfolkamateurradio.org/propagation-news-thursday-16th-april-2026/
9. stream1090 — CRC-Based Mode-S Demodulator, Never Misses a Packet
SDR TOOL
Skips preamble detection entirely — maintains CRC shift registers so a corrupted preamble cannot cause a missed ADS-B message. Single-bit error correction included. Pure C++, no extra libraries, runs on Raspberry Pi Zero 2W. Pipes into readsb or dump1090-fa.
GitHub source → github.com/mgrone/stream1090
10. ESP32 DX Cluster and Propagation Monitor — CYD Touchscreen, No PC Needed
BUILD / TOOL
The ₹800 ESP32 Cheap Yellow Display running real-time HamAlert DX spots alongside solar data from HamQSL. Touchscreen navigation, Wi-Fi configured from browser, auto firmware-update. A compact second screen at the operating position without tying up a PC.
GitHub source → github.com/hf7a/ESP32-ham-combo
Want to contribute? Found an interesting circuit, a new SDR software, a helpful radio blog, or breaking ham radio news? Email me or leave a comment below. Your link might be featured in next week’s digest!
