AM Radio Simulator

Semantic type: AMRadioSimulator · Category: lo-fi

Models bandwidth, distortion, interference, and noise associated with AM radio.

This type has catalog telemetry metadata but no public observation API in v0.1. See Compatibility.

Contract

• Seeded: yes
• Catalog sample rates: not declared; this does not mean unsupported
• Assets: none
• Catalog-declared latency: zero
• Telemetry: catalog metadata only; observation API unavailable in v0.1

EffeTune app documentation

The following section is reproduced from the English EffeTune app documentation. Its parameter names and values describe the app UI and can differ from semantic API parameters through transforms or value maps. The generated contract above is authoritative.

AM Radio Simulator

AM Radio Simulator transforms the music through a modeled AM broadcast chain: transmitter processing and modulation, groundwave and skywave propagation, static and adjacent-channel interference, receiver tuning and detection, AGC, and an optional radio speaker. Use it to compare a strong local station with a fading nighttime signal, explore a crowded dial, or give music the bandwidth, distortion, fading, and interference of AM reception.

This effect requires an environment that supports its real-time processing. When that processing is unavailable, the audio remains unchanged and the HUD reports that the effect is unavailable.

How It Differs from Additive Lo-Fi Effects

• AM Radio Simulator changes the input signal by modulating, propagating, filtering, and detecting it. Its static, interference, and hum enter at modeled points in the radio chain, so they interact with tuning, the IF filter, and AGC.
• Noise Blender adds a general background noise texture, while Hum Generator adds a controllable hum layer. Choose them when you want those sounds without changing the music through a radio receiver.
• Vinyl Artifacts adds record-style surface noise without changing the original music signal. Vinyl Simulator is another signal-transforming physical model, but it models a record groove and stylus rather than radio transmission.

Sound Enhancement Guide

• Clear local broadcast: Use a strong Signal, little Skywave and Static, centered Tuning, and a wider IF Bandwidth. Select Table for a fuller radio-speaker response or Off for line output.
• Nighttime distant station: Lower Signal, raise Skywave, and use a moderate Fading Speed. Slow AGC makes level recovery more gradual, while Static adds occasional lightning-like bursts.
• Crowded dial: Raise Interference and set Interf. Offset to 9 or 10 kHz. Narrow IF Bandwidth rejects more of the adjacent station; small Tuning changes alter how much reaches the detector.
• Broadcast overload: Raise Mod Depth above 100% or lengthen Detector RC to hear AM-specific overmodulation and diagonal-clipping distortion. Reduce either control for cleaner reception.
• Fade depth: New instances use 1% Skywave for gentler level movement in Mono and a less pronounced nighttime fade. Raise Skywave to about 8% when you specifically want a deeper fade; larger values make the effect more extreme.
• Start with Mix at 100% when judging the radio model. Lower it only when you intentionally want some of the original stereo image to remain.

C-QUAM Blend and Static Model

In C-QUAM, automatic stereo blending observes qualified signal loss on two orthogonal receiver axes: the decoded sum and the 25 Hz pilot region of the quadrature difference signal. AGC is removed from both observations, and a loss lowers the quality term only when it coincides on both axes. This loss-coincidence rule keeps ordinary program changes on either axis from being mistaken for an RF fade. It runs only while the PLL is tracking and the pilot is accepted; otherwise, the quality observation is cleared.

The new-instance Skywave default is 1%, adopted after the integrated model checks passed. Saved presets keep their explicitly stored Skywave value. Compared with 8%, the 1% setting gives Mono mode calmer level movement and shallower fades; select about 8% when a more severe nighttime-fade effect is wanted.

The frozen response range begins at Fading Speed 0.05 Hz. Attenuation that changes much more slowly than the adaptive reference’s 60 s fall time is absorbed into that reference and is intentionally not retained as a continuing quality loss. The 0.75 dB residual-program allowance, 0.04 ratio offset, Q=4 pilot observation band, 0.05/0.2/0.5/60 s quality time constants, and the 0.5 dB deadband with 5.0 dB transfer span are empirical simulator calibration, not general C-QUAM receiver specifications.

This receiver-faithful observation has the same program ambiguity as pilot C-QUAM hardware. If a program contains both difference energy near 25 Hz and asymmetric sum/DC, ending both components together can briefly lower the stereo blend because it presents the same RF evidence as a fade. A coherent anti-phase residual can likewise drive the quality observation while the PLL remains in TRACK and the pilot remains accepted. These are intentional behaviors within the approved model boundary, not defects.

Static events use a carrier-relative vector-area calibration: each event is scaled from a 20.0 µs area referenced to the nominal desired carrier, with an empirical uniform 0.5-to-1.5 area distribution and random phase. Events are scheduled from double-precision absolute deadlines rather than rounded sample countdowns, so timing remains continuous across render blocks and multiple events due in one sample are accumulated. The 20.0 µs scale and its distribution are empirical simulator calibration.

Parameters

Station

• Stereo Mode (Mono or C-QUAM) - Mono uses a traditional envelope-detector receiver. C-QUAM provides stereo reception, with lower stereo S/N than mono, and automatically blends toward mono when the signal is weak or mistuned. Because the receiver uses a physically different detector, switching modes can also change the timbre; Detector RC and its diagonal clipping apply only to Mono and have no effect in C-QUAM. C-QUAM stereo operates at sample rates up to 192 kHz; at higher rates, reception is mono. The simulation models only the FCC C-QUAM c(5) modulation-phase limit and does not represent a complete compliance test.
• TX Bandwidth (2.0 to 10.0 kHz) - Sets the transmitter’s audio bandwidth. Lower values sound darker and more restricted; higher values preserve more detail.
• Pre-emphasis (0 to 100%) - Boosts upper audio frequencies before transmission. Higher settings add presence but also drive bright peaks harder through the broadcast chain.
• Mod Depth (10 to 125%) - Sets AM modulation depth. Values above 100% create overmodulation and negative-peak clipping.
• Compression (0 to 20 dB) - Sets the depth of the broadcast limiter. Higher settings restrain peaks and make modulation more consistent.

Path

• Signal (-50 to 0 dB) - Sets received signal strength. Weaker settings expose more receiver noise and require more AGC gain.
• Skywave (0 to 100%) - Blends stable groundwave reception with delayed ionospheric paths. New instances default to 1% for gentle movement; around 8% gives a more severe nighttime fade, and higher values make the frequency-selective fading deeper.
• Fading Speed (0.05 to 2.0 Hz) - Sets how quickly skywave conditions vary.
• Static (0 to 100/s) - Sets the rate of lightning-like events. Each carrier-relative event follows an absolute-time schedule and rings through the receiver’s IF filter rather than being added after reception.
• Interference (-80 to 0 dB) - Sets adjacent-station strength. -80 dB switches it off; values closer to 0 dB make it stronger.
• Interf. Offset (5 to 10 kHz) - Sets adjacent-station spacing and the resulting carrier beat frequency. 9 and 10 kHz represent common channel spacing.

Receiver

• Tuning (-30.0 to +30.0 kHz) - Offsets the receiver from the desired station. Small offsets reduce clarity and increase asymmetric filtering distortion; at large offsets, the station falls below the receiver noise floor.
• IF Bandwidth (2.0 to 20.0 kHz) - Sets the receiver’s total IF passband. Narrow settings reject more noise and interference but remove more treble; wide settings retain more detail.
• AGC Speed (Slow, Mid, or Fast) - Sets how quickly automatic gain control follows signal changes. Slow emphasizes gradual recovery and pumping; Fast controls rapid fades more tightly.
• Detector RC (20 to 500 µs) - Sets the envelope detector’s discharge time. Longer values smooth the envelope more but increase high-frequency diagonal-clipping distortion at strong modulation.
• Hum (-80 to -20 dB) - Sets power-supply hum. -80 dB switches it off. Unlike an added hum layer, most of this control modulates receiver gain before detection.
• Hum Freq (50 or 60 Hz) - Selects the simulated power frequency.

Output

• Speaker (Off, Small, or Table) - Selects line output, a restricted pocket-radio speaker, or a fuller tabletop-radio response.
• Output Gain (-24 to +24 dB) - Adjusts level after receiver and speaker processing.
• Mix (0 to 100%) - Blends the original stereo signal with the simulated mono reception. 0% is unchanged stereo; 100% sends the same wet signal to left and right. Only 100% Mix makes the output fully mono.
• In C-QUAM, the wet signal is stereo when reception permits; the mono description above applies to Mono mode. Its FIR delay remains within the wet receiver path. Mix does not delay the dry signal to align it, so intermediate settings combine dry and wet signals with that timing difference.

Reading the HUD

• S METER shows, on an S1-to-S9 scale, the in-band signal strength the receiver has before AGC. Like the S meter of a real set it reads everything inside the passband, so the adjacent station, noise, and static lift it along with the station you want.
• AGC GAIN shows how much gain the receiver is currently applying. It normally rises as Signal falls or a fade deepens. It stops at +42 dB, so deeper fades and weaker signals remain quieter instead of being fully compensated.
• MODULATION shows the effective transmitter modulation percentage after transmitter filtering.
• FADE / EVENTS shows the current propagation gain change in dB and flashes with recent static and clipping rates. Frequent clipping suggests reducing Mod Depth or Detector RC when a cleaner result is wanted.
• STEREO follows the decoded stereo blend. It brightens as stereo reception opens and dims as the receiver automatically returns toward mono.

Recommended Settings

1. Strong Local Station
   • TX Bandwidth: 6.0 kHz, Mod Depth: 90%, Signal: -10 dB, Skywave: 5%, Fading Speed: 0.1 Hz, Static: 0.5/s
   • Interference: -80 dB, Tuning: 0 kHz, IF Bandwidth: 12 kHz, AGC Speed: Fast, Speaker: Table, Mix: 100%
2. Nighttime Distant Station
   • TX Bandwidth: 4.5 kHz, Signal: -35 dB, Skywave: 75%, Fading Speed: 0.3 Hz, Static: 6/s
   • Interference: -55 dB, Interf. Offset: 9 kHz, IF Bandwidth: 6 kHz, AGC Speed: Slow, Detector RC: 150 µs, Speaker: Small, Mix: 100%
3. Crowded Adjacent Channel
   • Signal: -25 dB, Skywave: 40%, Fading Speed: 0.5 Hz, Static: 3/s
   • Interference: -28 dB, Interf. Offset: 9 kHz, Tuning: +0.5 kHz, IF Bandwidth: 6 kHz, AGC Speed: Mid, Speaker: Small, Mix: 100%

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