HP / Agilent 3708A Noise and Interference Test Set

The HP/Agilent 3708A Noise and Interference Test Set is a precision instrument for evaluating communication system performance by injecting calibrated white noise and interference signals into IF sections of digital and FM radio systems. It maintains constant Carrier-to-Noise (C/N) and Carrier-to-Interference (C/I) ratios independent of input carrier power variations, enabling accurate C/N and C/I versus Bit Error Ratio (BER) characterization for microwave radio, satellite, and digital TV forward error correction (FEC) systems.

## Technical Specifications

**Noise Generation**
• Noise Type: Band-limited white noise
• Noise Output Level: +6 dBm to −80 dBm (filter-dependent); −70 dBm/Hz to −154 dBm/Hz (filter-dependent)
• IF Output Level: 6 dB lower than Noise Output connector
• Noise Power Accuracy: ±0.25 dB (+6 dBm to −10 dBm at 23 ±3°C); ±0.5 dB (+6 dBm to −55 dBm)
• Noise Bandwidth Accuracy: ±0.15 dB ±2.5%
• Crest Factor: Typically 15 dB

**Carrier Path (Reference Tone)**
• Oscillator Frequency: 70 MHz or 140 MHz, crystal-controlled, front-panel selectable
• Oscillator Level: 0 dBm ±0.15 dB (factory-set to 0 dBm ±0.05 dB at 23 ±3°C)
• Carrier Path Gain (70 MHz): 0 ±0.4 dB (typically 0 ±0.1 dB)
• Frequency Flatness: ±0.2 dB (70 ±20 MHz); ±0.3 dB (140 ±40 MHz)
• Group Delay: Typically 0.2 ns
• Loss to IF Output: Typically 15 dB

**Interference Path**
• Input Frequency Range: 10 MHz to 200 MHz, broadband
• Valid Interferer Input Power: −30 dBm typical

**Impedance & Connectors**
• Standard Configuration: 75 Ω unbalanced
• Option 001: 50 Ω unbalanced

**Measurement Performance**
• C/N Power Ratio Range: −10 dB to 60 dB
• C/N Accuracy: ±0.5 dB

## Key Features

• Microprocessor-controlled power metering maintains constant C/N and C/I ratios under varying input carrier conditions
• Broadband interference mixing capability stresses systems deterministically with or without simultaneous noise injection
• Crystal-controlled reference oscillator with selectable 70 or 140 MHz operation
• Dual-impedance connector options (50 Ω or 75 Ω) support diverse radio platforms

## Typical Applications

• Modem performance characterization in microwave radio and satellite systems
• Digital TV FEC system tolerance evaluation
• Fading simulation and system resilience assessment in digital and FM radio receivers
• BER measurement versus noise and interference ratio in communication link analysis