Audio Recording and Analysis

with on-screen video demodualtion


Audio Demodulation, Recording and Analysis

RadioInspector automatically records all detected AM and FM signals while scanning. Demodulation is possible over any frequency range provided by the instrument, from the maximum down to 200 Hz. For AM signals, phase- locked loop techniques may be possible. For receivers with audio output recording, analyzing and editing low-frequency demodulated audio signals is performed by the computer’s sound card. Scanning never stops to perform audio analysis while signals are captured, and their audio content is derived from the continual digital stream of the receiver. All analogue signals and analogue components of digital signals are demodulated using the built-in audio tuner, routed to the computer sound card for the operator to hear and are also recorded and stored for audio analysis by RadioInspector. Audio files can also be transferred across the network via the internet at operator selected sample rates. Audio can be recorded manually or automatically for signals that break an operator determined threshold. When starting a recording manually, RadioInspector saves the audio track for the 5 second period before recording was selected by the operator. An uncompressed wav format is used for recording to avoid the loss of quality and to allow complete processing of data including noise removal.


An unlimited number of audio files can be automatically collected and stored in the integrity protected database where they can be reviewed by the operator at a single button push via RadioInspector’s intuitive ‘Point and Click’ GUI. Using the audio analysis program, multiple audio files can be selected and played back sequentially, greatly facilitating the search for full duplex audio transmitting devices. The audio track editor enables analysis and editing of recorded audio tracks. Any portion of an audio file can be isolated and reviewed separately and saved as a new audio file.

Low Frequency Oscilloscope

A low frequency oscilloscope program displays the demodulated audio waveform and operators can select a bandwidth and choose a modulating signal recurrence period (auto correlation function) and display the resulting ACF spectrum wave form.

Audio Spectrum Analyzer

A demodulated audio spectrum analyzer can be added to the oscilloscope display with markers and cursors and an additional 1/3 octave spectrum bar graph can also be displayed.

RadioInspector’s low-frequency oscilloscope and demodulated audio signal spectrum analyzer feature enables analysis of temporal and frequency characteristics for a signal duration of up to 5 seconds. Using spectrum analysis techniques with different weighting functions, variable-length time, FFT conversion, averaging and multi-level auto-correlation processing of demodulated audio, it detects signals that are 20-30 dB below the noise floor.

Cursors support performing measurements in time and frequency domains and research of demodulated audio signals with periodic characteristics can be performed using the integrated auto-correlation signal technique.

Enhanced Digital Demodulators – Apco25 / DMR  / TETRA

Audio demodulation is provided for Apco25, DMR and TETRA communication standards (where encryption is not used), improving analysis capability during on-site or remote monitoring and spectrum surveillance applications.

A variety of additional information is also provided and displayed, where applicable, in the audio tuner and demodulation window including the date and time, frequency, communication standard identified, channel number, mobile or base station identification, condition (presence of audio, open channel, inactive channel, text / message transmission, private or group call etc.), source and destination identification, network color code, mobile country code (mcc) and mobile network code (mnc). For DMR (2 channels) and TETRA (4 channels) the operator can select a channel manually for monitoring and analysis or set the system for automatic channel switching.

RadioInspector can also be programmed to analyze, classify and automatically record audio for APCO25, DMR and TETRA signals that break an operator determined threshold. Programmed settings include adjusting the recording quality (sample rates Hz) and recording duration. The operator can also analyze signals manually by selecting a signal of interest from the main scanning GUI. The information displayed for each signal in the audio tuner and demodulation window can be saved and stored to individual files and re-loaded at any time for display. The information and can also be sent to a Microsoft Word document for print out and reporting applications.

Video demodulation (NTSC, PAL, SECAM)

RadioInspector’s built-in audio tuner and demodulation window can also be used to extract and demodulate video content from NTSC, PAL and SECAM signals. Demodulated video is displayed in a separate window with adjustment settings.

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