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