draft: false
Name: OffAir
short-description: AM/Shortwave/Longwave radio simulator with heterodyne whistles, SSB detuning and swelling static
summary: >-
  Tune across a virtual shortwave band the way you tune a real receiver. Two Stations and three
  interference signals are scattered across the dial and re-randomised on every band change.
  Approaching a Station you hear a sliding heterodyne whistle, the audio pulls into tune and the
  static ducks away; off-tune it frequency-shifts on SW and LW or distorts on AM. Knob X sets IF
  bandwidth and brightness, Knob Y the noise floor. Tap the switch down to cycle AM, SW and LW.
  Hold the switch up for dead air in baked-in mode, or a Pulse In 1-keyed morse Station 2 in
  audio-input mode. Pulse In 2 fires curated Insta-ference one-shots. Boot with the switch held
  down to swap the live inputs for baked recordings and make it self-contained.
Language: C++ (Pico SDK + ComputerCard)
Creator: Andy Jenkinson (uglifruit)
Version: 1.0.1
Status: Released
License: MIT
date-created: 2026-06-27
date-updated: 2026-08-04
repository: https://github.com/TomWhitwell/Workshop_Computer/tree/main/releases/95_offair2
discussion: https://discord.com/channels/1210238368898879569/1520467972089577623

contact:
  email: andyuglifruit@hotmail.com
  social:
    github: https://github.com/uglifruit

tags:
  - radio
  - sampler
  - noise
  - effect
  - generative

uf2:
  - path: offair.uf2
    name: OffAir v1.0.1

panel:
  inputs:
    - id: AudioIn1
      name: Station 1 In
      type: audio
      description: Station 1 source in audio-input mode; replaced by a baked recording in baked-in audio mode
    - id: AudioIn2
      name: Station 2 In
      type: audio
      description: Station 2 source in audio-input mode; becomes a keyed morse tone while the switch is held up
    - id: CVIn1
      name: Tuner
      type: cv
      description: Tuning offset added 1:1 to the Main knob, where ±5V covers roughly half the dial each way
    - id: CVIn2
      name: Noise
      type: cv
      description: Adds to the Knob Y noise level for voltage-controlled static
    - id: PulseIn1
      name: Shuffle Signals
      type: pulse
      description: Rising edge re-randomises the Station and interference layout. In audio-input mode with the switch held up it becomes the morse key instead
    - id: PulseIn2
      name: Insta-ference
      type: pulse
      description: Rising edge fires a one-shot from the curated Insta-ference bank, restarting if retriggered
  outputs:
    - id: AudioOut1
      name: Output
      type: audio
      description: Full mix of tuned audio, whistles, static and Insta-ference
    - id: AudioOut2
      name: Just Noise
      type: audio
      description: Noise and static only, for processing independently
    - id: CVOut1
      name: Signal Strength
      type: cv
      description: Envelope that rises as you tune onto a Station
    - id: CVOut2
      name: Station 1 CV Offset
      type: cv
      description: Station 1's offset from the Main knob — patch back into CV In 1, through a slew or direct, to hunt or lock onto Station 1
    - id: PulseOut1
      name: Station 1 Tuned Gate
      type: pulse
      description: Gate high while tuned to Station 1
    - id: PulseOut2
      name: Station 2 Tuned Gate
      type: pulse
      description: Gate high while tuned to Station 2

controls:
  switch:
    up:
      name: Dead Air / Morse
      description: Held. In baked-in audio mode this mutes both Stations while the interference and their CV and gate outputs continue; in audio-input mode Station 2 becomes a 600Hz morse tone keyed by Pulse In 1
    middle:
      name: Normal
      description: Standard tuning behaviour
    down:
      name: Baked-in Audio Boot
      description: Held at power-on until all six LEDs flash, this replaces the live inputs with baked recordings for a self-contained radio
    tap:
      name: Cycle Band
      description: A tap cycles AM to SW to LW, re-randomising the dial layout each time
  knobs:
    - main:
        name: Tuning
        description: Scans across the dial, summed with CV In 1
      x:
        name: Brightness
        description: IF bandwidth — sets both the Station capture width and the audio brightness, from narrow and muffled counter-clockwise to wide and bright clockwise
      y:
        name: Noise Level
        description: Static floor, silent fully counter-clockwise. Swells and swishes on its own, heaviest on LW, and ducks away when you tune onto a Station
  leds:
    - display: list
      items:
        - id: led0
          name: Station 1 Signal Strength
          description: Brightness rises as you tune onto Station 1
        - id: led1
          name: Station 2 Signal Strength
          description: Brightness rises as you tune onto Station 2
        - id: led2
          name: SW Band
          description: Lit on SW. With LED3 both off the band is AM
        - id: led3
          name: LW Band
          description: Lit on LW. With LED2 both off the band is AM
        - id: led4
          name: Unused
          description: Not used in this firmware
        - id: led5
          name: Tuning Position
          description: Indicates the current position across the dial

host:
  notes: |
    Audio-input mode boots with the switch in any position other than down, or released within
    the first 200ms, and the two live audio inputs become Station 1 and 2. Baked-in audio mode
    boots with the switch held down until all six LEDs flash, replacing the live inputs with
    baked recordings.

    The baked audio lives in clips.h, generated from your own source files by convert_clips.py —
    the source audio is not included in this repo. See the README for the conversion workflow and
    the roughly 2MB flash budget.