The HP/Agilent 5351B is a continuous-wave microwave frequency counter delivering direct measurements from 10 Hz to 26.5 GHz without external mixers. Engineered for precision frequency measurement in microwave communication and radar system testing, this instrument combines fast acquisition with high sensitivity across its full operating range. Its automatic amplitude discrimination identifies and measures the highest-amplitude signal in multi-signal environments, while selectable resolution from 1 Hz to 1 MHz accommodates both coarse and fine measurement requirements. The counter achieves sensitivity to −40 dBm typical at 25°C in the 500 MHz to 12.4 GHz band, with improved performance available via optional configurations. Input impedance is user-selectable between 1 MΩ nominal (shunted by <70 pF) and 50 Ω nominal, supporting both DC-coupled and AC-coupled measurements through a replaceable BNC connector. Fast-acquisition tracking reaches 1 GHz/s with 60 ms automatic lock time; manual mode settles in 20 ms. HP-IB integration enables measurement throughput exceeding 100 readings per second in automatic mode, scaling to 120 readings per second in dump mode with 10 kHz resolution. Frequency accuracy is ±1 LSD ±(time-base error × frequency). The 5351B handles input signals from −32 dBm to +7 dBm at standard specification, with damage protection at +25 dBm. Option 002 and Option 006 configurations improve both sensitivity and maximum safe input levels across the full frequency range, enabling operation in demanding signal environments requiring extended dynamic range or protection against high-level interferers.
## Technical Specifications
• **Frequency Range:** 10 Hz to 26.5 GHz
• **Resolution:** Selectable 1 Hz to 1 MHz
• **Accuracy:** ±1 LSD ±(time-base error × frequency)
• **Sensitivity (500 MHz–12.4 GHz):** −32 dBm specification / −40 dBm typical @ 25°C
• **Sensitivity (12.4–20 GHz):** −27 dBm specification / −35 dBm typical @ 25°C
• **Sensitivity (20–26.5 GHz):** −16 dBm specification / −28 dBm typical @ 25°C
• **Maximum Input:** +7 dBm; +10 dBm (50 Ω BNC)
• **Input Impedance:** 1 MΩ nominal (100 measurements/second (automatic), 120 readings/second (dump mode)
• Option 002 and Option 006 configurations improve sensitivity and input handling across all bands
## Typical Applications
• Microwave communication system testing and commissioning
• Radar system frequency verification
• Component characterization and troubleshooting
• Low-level signal detection and measurement
## Compatibility & Integration
• HP-IB (GPIB) interface for remote control and data logging
• BNC female connector with user-selectable impedance
• AC/DC coupling modes support diverse signal sources
