FAQ

FAQ

Answers for new operators and for hams evaluating Nexus against the tools they
already run. Nexus is in open beta: the FT8/FT4 core is production-grade and
verified against WSJT-X behavior; the newest features are fresh from the bench and
field reports are wanted.

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Operating and modes

Is this a WSJT-X replacement?

For FT8 and FT4 operating, that's the goal. The sequencer is built to
WSJT-X's behavior and verified against a 207-row parity matrix, and Nexus adds
things stock WSJT-X doesn't have — country and worked-before flags on every
decode, one-click "work it" that jumps band/mode/frequency together, and a Needed
board that ranks the stations on the air by what they're worth to your log.

But WSJT-X still has more modes (Q65, MSK144, WSPR, and others Nexus does not
implement), and it runs on macOS and Linux where Nexus ships Windows only today.
Nexus speaks WSJT-X's UDP protocol, so it isn't all-or-nothing — your
GridTracker / JTAlert / logger workflow survives either way.

What is FT1, in one sentence?

FT8's message set on a 4-second cycle with cellular-style retransmission combining
— keyboard chat at conversation speed, still down in the weak-signal noise (open
beta; simulation-validated).

Is FT1 more sensitive than FT8?

No — and this is the most important thing to understand about it. FT1 trades
roughly 6 dB of raw single-shot sensitivity against FT8 (about 2.5 dB against
FT4) for a nearly 4× faster cycle plus an IR-HARQ path that lets weak
retransmissions combine instead of being wasted. FT8's ~−21 dB threshold is the
most sensitive here; FT1's ~−15 dB sits about where FT4 does. Those numbers are
simulation-validated only. If you want maximum reach in one shot, use FT8; if
you want a conversation, use FT1. When the path is fading, use DX1.

What is DX1?

The robust tier: non-coherent 8-FSK on a 15-second cycle, built to shrug off the
fading that collapses coherent modes (a ~3.7 dB fading penalty in simulation,
where coherent modes lose 10+ dB). It gives up some raw sensitivity to stay
decodable on NVIS, polar, and rough paths.

Are the FT1/DX1 performance numbers proven?

They are simulation-validated — AWGN and Rayleigh-fading bench sweeps,
re-checked in the test suite and the Windows cross-build. They are not on-air
proven. Decode-rate-versus-SNR on real bands is the project's #1 remaining gate,
and it's what the open beta exists to establish. Every dB figure Nexus publishes
is labeled "simulated" for exactly this reason.

How do I help the beta?

Send honest on-air reports: band, dial frequency, which tier (FT1 or DX1),
distance and rough conditions, and what you decoded versus what you expected —
including the surprises (false decodes, retransmissions that combined, stations
you saw that others didn't). Field reports are the single most useful contribution
right now. Open a ticket on the SourceForge tracker at
https://sourceforge.net/p/nexus-ham-radio/tickets/.

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Setup and safety

Do I need to install Hamlib, WebView2, or drivers first?

No. Hamlib (for CAT and rotator control) and the WebView2 runtime are bundled
in the installer, so Nexus works on a bare PC with no separate installs. If Windows
is missing a USB bridge-chip driver for your rig's interface, the first-run wizard
detects that and gives you the right download link.

Will Nexus transmit on its own?

Never on launch. Nexus starts passive — it listens. Every transmission is an
explicit operator action (you send a message, answer, or call CQ). On top of that
there's a transmit watchdog and a license-class lockout (Technician / General
/ Extra per Part 97, including the 2026 60 m rules) — a software guard in every TX
path that blocks transmit outside your privileges. The presence beacon is off by
default.

About 50 rigs are "supported" — is mine one?

Around 50 rigs are curated out of the box (Icom including the IC-9700 and IC-705;
Yaesu FTDX10, FT-991A, FT-710; Kenwood; Elecraft; FlexRadio; Xiegu; QRP Labs QMX
and more), and Hamlib is bundled, so CAT and rotator control work offline. "Detect
my radio" scans USB and finds FlexRadios on the LAN, then fills in the model, port,
and paired audio in one click. See Rig Setup for the per-brand path.

Field-verified so far: the FTDX10 and FT-991A (on real hardware, by the
author). Other rigs use Hamlib's well-established support but haven't each been
bench-verified in Nexus specifically — this is a beta, and confirming your
particular rig is useful feedback.

What's the story with FlexRadio and Xiegu?

Both work today over Hamlib CAT — Flex via SmartSDR's network CAT, Xiegu over
serial — and Flex is discoverable on the LAN with one-click DAX audio pairing.
Honest status:

• FlexRadio: the FLEX-6400M CAT path is in final verification on hardware.
  The deeper native SmartSDR integration (slices, panadapter, DAX as first-class
  objects) is deferred to a later phase — today Flex is driven as a network-CAT
  rig, not through the native SmartSDR API.
• Xiegu: supported via Hamlib CAT (e.g. the G90), but not yet verified on
  hardware in Nexus. If you run one, a field report is welcome.

Why is the download about 210 MB?

Because everything is bundled: the WebView2 runtime, Hamlib (CAT + rotator), and
the whole DSP stack. That's the tradeoff for working offline on a bare PC with no
separate installs and no admin rights — a per-user install that just runs.

Why does the installer warn that it's unsigned?

Nexus ships unsigned today, so Windows SmartScreen will show a warning when
you run the installer. This is expected for a beta from an individual developer —
code-signing certificates are a paid, identity-verified process. To install
safely, verify the SHA-256 hash of the download against the value published on
the download page before running it, then click "More info → Run anyway". The full
walkthrough is on the Install page.

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Data, licensing, and platforms

Where does my data go?

Your log stays local, in an ADIF file on your machine. Uploads happen only
to the services you explicitly configure — LoTW, QRZ, ClubLog, eQSL, HRDLog.net —
and those credentials live in the Windows keychain, never in a plaintext
config file. Journey/achievement progress never leaves your computer. Nexus has no
telemetry or analytics phone-home; the only outbound traffic is the connectors you
turn on and, by default, PSK Reporter spot uploads (which you can disable).

Is Nexus really free? What's the license?

Yes — Nexus is free and open source under the GPL-3.0. There's no paid tier,
no subscription, and no "pro" upsell. The GPL means you get the complete source,
you can study and modify it, and any distributed derivative must also be GPL-3.0.
Nexus builds on WSJT-X's GPL heritage (the 77-bit message packing, LDPC FEC, and
FFTW infrastructure), which is why the shared message layer is compatible with the
modes you already run.

Where is the source code, and can I contribute?

The repository is https://sourceforge.net/p/nexus-ham-radio/code/ci/main/tree/. Contributions are welcome —
issues, field reports, and pull requests all help. The most valuable contributions
during beta are on-air decode reports for FT1 and DX1 and rig confirmations
for radios beyond the two the author has bench-verified.

Mac or Linux?

Not yet as a shipping build. The codebase is cross-platform Rust/Tauri, but only
the Windows installer ships today (built, in fact, by cross-compiling from
Linux). If you want a native macOS or Linux build, say so on the ticket tracker —
interest is what prioritizes it.

Will there be automatic updates?

Not in this beta — there's no auto-updater yet. Watch the download page (and verify
the SHA-256 of each new download) to update manually.

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More: Quick Start · Install · Rig Setup
· Documentation · the deep protocol docs on
SourceForge.

License: GPL-3.0 · by KD9TAW · Repository:
https://sourceforge.net/p/nexus-ham-radio/code/ci/main/tree/