If you have a Leo Bodnar LBE-1421 GPS clock and a Mac, MacGPSDO does what the Windows config tool does, plus sky plots for GPS, Galileo and GLONASS, Allan deviation, 1PPS sawtooth, RF health, and a 1 Hz log you can scroll back through. rfspace.com/RFSPACE/MacGPSDO…

Remote HF, no PC at the radio: @Icom_Inc_Japan IC-7300MK2 → Ethernet → pocket travel router → Tailscale → Starlink Mini → SpectraRemote on an M4 Mac mini. Three UDP ports, hand-rolled keepalives, your own sequence numbers. None of it documented. You find out by sniffing packets and diffing against a client that already works. Every 90 seconds the radio asks if you're still there. Miss one reply and it keeps streaming a gorgeous waterfall while ignoring every command you send. Not broken. Offended. Recovery procedure: power cycle. Trivial, unless the radio is in Zimbabwe and you are not. A 2026 mesh VPN carrying a protocol that still thinks it's on a LAN in 1996. And it works! 😂🤣

IC-7300 MK2 over ethernet now stable.

Grok 4.6 is on it.

Every open source AIS demodulator I could find is GPL. Here's one released under MIT. libaisdemod: complex IQ in, AIVDM sentences out. Both channels from one tune. C99, no dependencies. github.com/ibelinp/libaisdem…

MIT-licensed FT8/FT4 decoder in Rust. Every other one I found is GPL or has no license at all. One dependency, runs in the browser via wasm. github.com/ibelinp/ft8

New display for my ADS-B tracker: azimuth/elevation instead of a map. I wanted one display I could reuse across the satellite tracker, spherical waterfall, GNSS monitor, and passive radar apps. With a scanning receive array, passive radar returns come in as az/el, so this gives me a way to match returns to aircraft. Multi-site passive obs solve straight to lat/lon, which is what the map is for. Pluto SDR on an indoor antenna, so signals are weak, but that's real traffic. Runs on iPad too, with the Pluto over USB. Nice feature to be able to apply all my waterfall colormaps to flight level, speed, RSSI or range.

I wanted my LBE-1421 to display Glonass and Galileo

Watching airplanes do touch-and-gos at PDK from my desk tonight, with a single active vertical antenna (R&S HE600) sitting inside my room and zero watts transmitted. The illuminator is Atlanta's ATSC 3.0 TV tower, 7 km away. The airplane is the faint diagonal streak. It took a complete ATSC 3.0 receiver written from the spec (bootstrap sync, L1 decode), then using the broadcast's scattered pilots as a free channel sounder, about 400 soundings per second. Stack 96 of those into a range-Doppler map, integrate 4 seconds, run CFAR, and an echo some 60 dB below the direct signal.

A slot antenna is a hole that radiates. Cut a narrow rectangle out of a large conducting sheet and feed it across the short dimension. The radiation pattern looks almost exactly like a dipole of the same shape, except E and H are interchanged and the polarization is rotated 90°. This is Babinet’s principle (optics to antennas via Booker, 1946). Take any thin conducting screen and its exact complement (metal where there was free space, free space where there was metal). Illuminate both with the same wave. The fields they produce, E₁ and E₂, must satisfy: E₁ + E₂ = E₀ where E₀ is the field that would exist with no screen at all. In the geometric shadow the two diffracted fields are equal in amplitude and opposite in phase. Everywhere else they add to the unobstructed wave. That’s why a slot and its complementary strip dipole are duals: the hole and the cover together recreate free space. Their impedances are locked by Z_slot · Z_dipole = (η/2)² (~35 000 Ω²). A 73 Ω half-wave dipole becomes a ~480 Ω slot. The metal isn’t doing the radiating. The absence of metal is. And the sum of the structure and its hole is required to be nothing more exotic than ordinary free-space propagation. Nature’s neatest antenna trick: the thing you remove is just as important as the thing you leave.

Quick test of Skywave Web SDR. The server sends compressed IQ, your browser does the demodulation. Runs on a Raspberry Pi, tested to 256 listeners. Right now it's playing an AO-40 pass I recorded 23 years ago on pi day 2003, with the @rfspace SDR-14. skywave.sdranywhere.com

25 Msps of FM band as .biq at 8, 6 and 4 bit pairs. Same ref level: the stations don't move, only the noise floor climbs. 4th shot is the 4-bit file with the ref level autoscaled and still decoding RDS. Same 500 MB: 5s at 16 bit pairs, 10s at 8, 13s at 6, 20 s at 4.