HEWLETT PACKARD 420C CRYSTAL DETECTOR

The Hewlett Packard 420C is a broadband crystal detector engineered for sensitive detection and measurement of microwave signals across a wide frequency span. It converts microwave energy into measurable DC voltage via a point-contact semiconductor diode, enabling precise power measurements in laboratory and field applications. The detector delivers repeatable performance with low noise and configurable output polarity, making it suitable for both general-purpose signal detection and specialized measurement tasks.

Technical Specifications

Frequency Range: 0.01 GHz to 12.4 GHz Sensitivity

• Low-level: >0.15 mV/µW


• CW: >0.4 mVdc/µW


• With load resistor: 0.1 mV/µW Input Impedance: 50 ohms Output Impedance: 15 kΩ shunted by 10 pF Reflection Coefficient (SWR)


• 10 MHz to 4.5 GHz: 0.091 (1.2 SWR)


• 4.5 GHz to 7.0 GHz: 0.15 (1.35 SWR)


• 7.0 GHz to 12.4 GHz: 0.2 (1.5 SWR) Maximum Power Input: 100 mW peak or average; 0.1 W short-term (<1 min) Frequency Response: ±2 dB overall. With video load: <0.5 dB variation from square law over ≥30 dB dynamic range to 50 mV peak output into 75 kΩ external load. Temperature coefficient: 0.015 dB/°C (0°C to 55°C) Output Noise: 200 µV peak-to-peak Output Polarity: Negative standard; positive available (Option 03) Detector Element: Point-contact type, field-replaceable Connectors


• Input: Type N (male or female per option)


• Output: BNC female Physical: 4.5 inches (144 mm) overall length

Key Features

• Flat ±2 dB response across 0.01–12.4 GHz


• Low reflection coefficient enabling minimal signal disturbance


• Square-law conformance option for envelope detection applications


• Field-replaceable point-contact diode element


• Configurable connector and polarity options

Typical Applications

• Pulse envelope observation and demodulation via oscilloscope


• Microwave signal detection and power measurement


• Reflectometer component integration


• Harmonic-frequency comparison measurements using mixer configuration

Compatibility & Integration Standard Type N input connector (male or female) accommodates industry-standard waveguides and coaxial transmission lines. BNC output enables direct connection to oscilloscopes, high-impedance measurement instruments, and signal-processing equipment. Matched-pair option (001) and video-load option (002) support demanding measurement scenarios. Stainless steel connector versions (options 012, 013) extend operational durability in demanding RF environments.