The Agilent/Keysight 85680B RF Preselector is a front-end accessory that enhances spectrum analyzer measurement performance by integrating tracking filters and preamplifiers. Designed for the 8568B and 8566B spectrum analyzers, this unit reduces out-of-band signal overload and boosts system sensitivity to enable accurate weak-signal detection in high-interference environments. The preselector operates across three distinct frequency ranges and includes a transient limiter on the low-frequency input for LISN protection. It is fully programmable via HP-IB (IEEE-488) and delivers the measurement precision required for EMC testing, radiated emission surveys, and conducted immunity assessments.
Technical Specifications
• Frequency Range (Input 1): 20 Hz to 50 MHz
• Frequency Range (Input 2): 20 MHz to 2 GHz
• Bypass Mode: DC to 18 GHz
• Preamplifier Gain: 20 dB nominal (at 0 dB RFP attenuation)
• Stopband Attenuation: >40 dB nominal
• Power Requirements: 100, 120, 220, or 240 V RMS ±5%, −10%; 50–400 Hz; 35 VA nominal
• Operating Temperature: 0° to +55°C
• Storage Temperature: −40° to +75°C
• Warm-up Time: 30 minutes after cold start; 2 hours for thermal equilibrium
• Dimensions: 133 mm H × 425 mm W × 508 mm D
• Weight: 19 kg net
– Key Features
• Tracking filters attenuate out-of-band interference and reduce dynamic range compression
• Dual-input architecture supports both low-frequency (conducted) and RF (radiated) measurements
• Transient limiter on Input 1 protects against LISN-generated impulses
• Built-in calibrator ensures ±2.0 dB absolute amplitude accuracy
• Linearity check function detects system overload and harmonic distortion
• Full programmability via HP-IB for automated test sequences
• Compliant with CISPR 16 for EMI receiver systems
– Typical Applications
• EMC/EMI testing (FCC and VDE radiated emission surveys)
• Conducted emission measurements (commercial and MIL-STD standards)
• Signal surveillance in presence of strong interference
• Low-level signal detection requiring high selectivity
– Compatibility & Integration
The 85680B interfaces directly with Agilent/Keysight 8568B and 8566B spectrum analyzers. Optimal EMI receiver performance is achieved when paired with the 85650A QPA. Firmware compatibility spans multiple versions: 8566B (all versions), 8566A (any version), 8568B firmware ≥14.1.85, and 8568A (any version).
