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About

Two callsigns, one operator

I'm James Xue — a student, developer, and amateur-radio operator working as BD1DMB from the Beijing region (grid OM89) and KD3CSB from New Castle, Delaware (grid FM29).

BD1DMB
KD3CSB
Beijing · OM89
Biography

A student who fell in love with the spectrum

I'm a high-school student and self-taught developer who got pulled into amateur radio the first time a handful of watts carried my voice to a stranger on the other side of a mountain. That little miracle — that radio works at all — has shaped almost everything I've built since.

By day I write code: web applications, data pipelines, and increasingly the retrieval-augmented AI systems that are quietly rewiring how software answers questions. By night I'm in the shack, chasing weak signals, decoding satellite telemetry, and logging contacts that turn a map of the world into a list of people I've actually spoken to.

The two halves aren't separate. Radio taught me to respect physics and noise floors; programming gave me the tools to bend them. Somewhere in the overlap — SDR, DSP, embedded systems, and the maths of orbits — is the work I most want to do, and the reason this station exists in the first place.

At a glance

Operator
James Xue
Callsigns
BD1DMB · KD3CSB
Grid
OM89
QTH
Beijing region, China
Mode
FM · SSB · CW (CWO)
Roles
Student · Developer · Ham
Education

Learning, formally and at the bench

The classroom matters, but most of what I know about radio and code came from breaking things and fixing them again.

Secondary school

Currently a high-school student focused on mathematics, physics, and computer science — the foundation under every link budget and flowgraph I touch.

Self-directed RF & software

Licensed amateur and self-taught developer: antenna theory, DSP, GNU Radio, full-stack web development, and the AI systems I build to learn the rest faster.

Technical interests

Where radio, code, and space overlap

The recurring themes across the projects, the logbook, and the late nights.

Satellites & the ISS

Working FM and linear birds — SO-50, the RS-44 transponder, and APRS digipeating through the ISS. Doppler-corrected passes are equal parts orbital mechanics and antenna craft.

Software-Defined Radio

Living in the waterfall with an RTL-SDR and an SDRplay: decoding weather satellites, hunting weak HF signals, and writing GNU Radio flowgraphs to demodulate the modes commercial rigs ignore.

RAG & applied AI

Building retrieval-augmented systems that ground large language models in real documents — vector search, embedding pipelines, and evaluation harnesses for answers you can actually trust.

Audio & DSP

From SSB filters to room acoustics: digital signal processing is the thread connecting radio, music, and code. I build small tools for analysis, filtering, and clean monitoring.

Orbital mechanics & KSP

Kerbal Space Program turned delta-v budgets and Hohmann transfers into intuition. It is the most fun anyone can have learning why rockets are hard and rendezvous is harder.

Space science

Tracking launches, reading mission profiles, and understanding the link budgets that let a few watts reach a spacecraft. Radio is how humanity talks to everything beyond the atmosphere.

Future goals

The roadmap from here

Concrete, dated-when-I-can-make-them ambitions for the station and for me.

01

Stand up the school amateur-radio station

Get a club callsign on the air with a working HF/VHF setup, train the first cohort of student operators, and run a satellite demo that turns a passing spacecraft into a classroom.

02

University study in engineering & CS

Read electrical engineering and computer science at a strong programme — formalising the RF, DSP, and systems knowledge I have been building hands-on at the bench.

03

Earn DXCC

Confirm 100 distinct DXCC entities from grid OM89 — a long, patient project across HF openings, satellite footprints, and careful logging and QSLing.

04

Operate KD3CSB from the US

Upgrade the US licence and put KD3CSB on the air from the field — bridging two callsigns, two regulatory worlds, and cross-continental contacts.

Timeline

Milestones on the air and off

A running log of the moments that built the station.

  1. Award

    Worked the ISS

    First contact through the International Space Station

  2. Radio

    Founded the school radio club

    Began mentoring students toward their licences

  3. Project

    Started the Industrial HMI RAG system

    Production retrieval-augmented assistant

  4. Radio

    Obtained US callsign KD3CSB

    Passed the FCC Technician exam

  5. Project

    Began the Caffeine app

    Started building my macOS focus app

  6. Radio

    First satellite QSO

    Made a contact through SO-50

  7. Project

    Started the AI Agent Experiments lab

    Began exploring tool-using LLM agents

  8. Radio

    First HF DX contact

    Worked Japan on 20m SSB

  9. Radio

    Licensed as BD1DMB

    Earned my Chinese amateur radio licence

Achievements

Awards & confirmations

Certificates, contest finishes, and the operating awards worth framing.

DXCC

DXCC (in progress)

ARRL

Worked 80+ DXCC entities across HF

Jan 2026

Award

Worked All Continents

IARU

Confirmed contacts on all six inhabited continents

Sep 2025

Satellite

Satellite Communicator

AMSAT

Multiple confirmed satellite QSOs incl. the ISS

Apr 2026

Milestone

CW operator milestone

Built reliable CW copy and logging practice across HF contacts

Dec 2025