Monitoring broadcast signals
Continuous monitoring of broadcast signals is essential for maintaining service quality and operational continuity in transmission networks. Detecting, analyzing, and verifying FM, DAB, and DVB-T2 transmissions in real time is a core requirement for broadcasters, network operators, and critical infrastructure managers.
Broadcast networks are growing in complexity, and meeting high quality standards requires professional monitoring systems capable of operating continuously under any environmental condition. Choosing the right instrumentation is decisive for preventing service outages and optimizing network performance.
Broadcast technologies: FM, DAB, and DVB-T2
FM — Frequency Modulation (88–108 MHz)
Frequency modulation remains the most widely deployed audio broadcasting technology worldwide. Operating in the VHF band between 88 and 108 MHz, FM delivers quality audio transmissions over broad geographic areas. The technology uses frequency deviation proportional to the amplitude of the modulating signal, giving it greater immunity to interference than amplitude modulation.
From a technical standpoint, each FM station occupies approximately 200 kHz of bandwidth, with a maximum deviation of ±75 kHz for the main audio signal. Monitoring FM transmissions requires analysis of parameters including: received signal level (RSSI), frequency deviation, presence of the 19 kHz pilot carrier, and modulation quality.
DAB — Digital Audio Broadcasting (174–240 MHz)
DAB is the digital evolution of audio broadcasting and operates primarily in VHF Band III (174–240 MHz). The technology uses OFDM (Orthogonal Frequency Division Multiplexing) modulation with MPEG Audio Layer II coding in the original version and HE-AAC v2 in the DAB+ variant — today the on-air standard in Italy — enabling transmission of multiplexes carrying multiple radio services within a single 1.536 MHz frequency block.
The DAB signal structure is based on 96 ms transmission frames divided into OFDM symbols. Each DAB ensemble can carry up to 64 audio and data services, with variable bitrates from 8 to 384 kbps per service.
DVB-T2 — Digital Video Broadcasting Terrestrial 2 (470–694 MHz)
DVB-T2 is the second-generation standard for terrestrial digital television and operates in the UHF band between 470 and 694 MHz (following the 700 MHz band refarming completed in Italy in 2022, the 694–790 MHz range is allocated to mobile services). Compared to DVB-T, it delivers a 30–50% increase in transmission capacity through technologies including modulation up to 256-QAM, LDPC (Low Density Parity Check) coding, and constellation rotation.
DVB-T2 supports flexible configurations with channel bandwidths of 6, 7, or 8 MHz, multiple FFT modes (1K, 2K, 4K, 8K, 16K, 32K), and variable guard intervals. The signal structure is based on super-frames composed of T2-frames, enabling transmission of multiple PLPs (Physical Layer Pipes) with differentiated robustness parameters for HD, SD, and data services.
The three technologies compared
| Technology | Band | Modulation | Channel |
|---|---|---|---|
| FM | 88–108 MHz (VHF II) | Analog FM, ±75 kHz deviation | ~200 kHz |
| DAB / DAB+ | 174–240 MHz (VHF III) | OFDM | 1.536 MHz block |
| DVB-T2 | 470–694 MHz (UHF) | OFDM, up to 256-QAM | 6 / 7 / 8 MHz |
Parameters to monitor
Professional monitoring of broadcast signals requires continuous analysis of key RF parameters. Received signal level, expressed in dBm or dBµV, is the primary indicator of geographic coverage. Tracking how this parameter changes over time reveals propagation problems, interference, or transmitter faults.
Spectral analysis enables verification of channel occupancy, identification of spurious emissions, and detection of co-channel or adjacent-channel interference. The resolution bandwidth (RBW) of the measurement instrument must be matched to the signal type: typically 3–10 kHz for FM, 10–30 kHz for DAB, and 30–100 kHz for DVB-T2.
Monitoring methodologies
24/7 continuous monitoring
A continuous monitoring system requires equipment designed to operate uninterrupted under extreme environmental conditions. IP67 certification provides complete protection against dust and temporary immersion — an essential requirement for outdoor installations on towers, in tunnels, or at remote sites.
The monitoring architecture must include historical data storage for trend analysis and retrospective fault diagnosis. Recording parameters at an adequate time granularity (typically samples every 1–10 seconds) makes it possible to identify intermittent problems and correlate them with external events.
Alert and notification systems
An effective monitoring system must include multi-level alert mechanisms based on configurable thresholds. Alarms can be triggered by: carrier absence, signal level degrading below minimum thresholds, error threshold exceedance, or abnormal variation in modulation parameters.
Notifications must be distributed across multiple channels: email for non-critical alarms, SNMP traps for integration with network management systems, relay outputs for activating backup systems, and a web dashboard for real-time network status visualization.
Practical implementation
The TP-RFX system for broadcast monitoring
The TP-RFX is Teleproject's solution for outdoor monitoring of broadcast signals. Operating across the 15–2700 MHz band, it gives complete coverage of FM, DAB, and DVB-T2 frequencies. IP67 certification and an operating range of 0–50 °C ensure reliability in outdoor installations.
PoE power supply simplifies installation by eliminating the need for local power adapters, while the N-type connector ensures compatibility with professional antenna systems. The dynamic range from −130 dBm to +10 dBm, with protection up to +30 dBm, enables accurate measurements across a wide range of operating conditions.
The integrated web dashboard provides real-time spectrum visualization, configuration of multiple channels for simultaneous FM, DAB, and DVB-T2 monitoring, measurement history for time-based analysis, and a configurable notification system via email, SNMP, and relay.
Professional monitoring of FM, DAB, and DVB-T2 broadcast signals is essential for ensuring service quality and continuity. Dedicated RF analysis systems — designed for outdoor operation and equipped with alerting and historical logging functions — prevent service disruptions and optimize broadcast network performance.
Selecting the right instrumentation, paired with a sound monitoring methodology, is a strategic investment for broadcasters and network operators.
Frequently asked questions
What parameters need to be monitored in broadcast signals?
Received signal level (in dBm or dBµV), channel occupancy, and carrier presence; for FM also frequency deviation and the 19 kHz pilot carrier. How these parameters change over time reveals propagation problems, interference, or transmitter faults.
Can a single instrument monitor FM, DAB, and DVB-T2?
Yes — you need an analyzer with adequate frequency coverage. The TP-RFX covers the 15–2700 MHz band and simultaneously monitors multiple FM, DAB, and DVB-T2 channels from a single measurement point.
Where is a broadcast monitoring system installed?
At representative points within the service area: towers, elevated sites, tunnels, or remote locations. You need outdoor-rated equipment with IP67 protection and a simple power supply — PoE eliminates the need for a local power adapter.