AM Broadcast Processor

Share on Facebook Share on Twitter


The Model 235 incorporates all audio processing needs for AM broadcasting in a single, easy-to-use package. "Gain-riding" AGC is followed by variable low- and high-frequency EQ, 3-band compression, an asymmetrical, integrated limiter/clipper peak controller, and a low-pass function that satisfies NRSC or other "audio mask" specifications. A rear-panel RS-232 data port allows the processing presets to be programmed or updated by computer or modem; the necessary software is included.

"...Used in AM broadcasting, this small processor packs an audio punch..."


  • One-box audio processing for mono-AM broadcasting

  • Variable equalization and asymmetrical peak control

  • NRSC-compliant & AMAX-certified

  • Gated-AGC (Automatic Gain Control)

  • 3-band Compression/Equalization

  • Limiting and low-pass filtering

  • Full remote control by computer or modem (RS-232 interface)

  • Optional cutoff frequencies available (9kHz, 6.4kHz & 5kHz)



..."Inovonics’ AM processor is the 235. It’s a single-rack unit box, with AGC, a three-band compression and equalization section, peak limiting and low pass filtering. It’s NRSC-compliant but also offers other cut-off frequencies: 9 kHz, 6.4 kHz, or 5 kHz. Control of the 235 can be accomplished by rs-232, meaning use of a local PC (which of course can give you remote access assuming your transmitter site has IP access)."...

- Doug Irwin, CPBE AMD DRB There’s an Art to On-Air Processing


Frequency Response

±1dB, 50Hz–9.7kHz* (taken through NRSC de-emphasis network and with processor EQUALIZATION set “flat”). * US NRSC (10kHz) version. Alternative cutoff frequencies for CCIR channel spacings and for various short-wave protocols are optionally available at slight additional cost.


Typically under 1% THD at any PROGRAM DENSITY setting, and at PEAK PROCESSING settings which maintain negligible clipping depth.


Better than 60dB below full carrier modulation (assuming NRSC de-emphasis).

Fixed Pre-Emphasis

The US version follows the “truncated” 75μs curve specified by the NRSC transmission standard. Alternative versions employ pre-emphasis appropriate to the cutoff frequency.

Variable Equalization

  • HF: –3dB, 0dB (flat), +3dB, +6dB, MAX. (These figures are independent of, and in addition to, the NRSC or alternative fixed pre-emphasis).

  • LF: –9dB, –6dB, –3dB, 0dB (flat), +3dB

Processing Variables

  • PROGRAM DENSITY controls “blending” within the triband compression section, as well as the compressor release characteristic. Eight incremental settings range from a slow, single-band function to fast, fullyindependent 3-band operation.

  • PEAK PROCESSING programs the action and interrelation of the peak limiter and clipper circuits in eight MIN to MAX increments.


Active-balanced, bridging; accepts nominal program line levels between –15dBu and +15dBu.


Active-balanced, 200-ohm resistive source; delivers 0dBm to +15dBm into 600 ohms.

Output Asymmetry

Positive peak amplitude is continuously variable between +100% and +130%.

Remote Control Provision

An RS-232 serial data port (DB9 connector) allows all processing presets to be programmed by an IBMcompatible computer, directly or via modem. Supplied software runs under Microsoft Windows® 95/98.

Power Requirements

105-130VAC and 210-260VAC; 50/60Hz; 20W.

Size and Weight

  • 23” x 16” x 2” (2U); 10 lbs

  • 584mm x 406mm x 51mm ; 4.5 kg