HP 774D Dual Directional Coupler 215-450 MHz -20 dB N-Type Connectors

HP 774D Dual Directional Coupler 215-450 MHz -20 dB N-Type Connectors

The HP 774D is a passive dual directional coupler designed for RF signal sampling and power monitoring across a frequency range of 215 to 450 MHz. It provides two coupled output ports — one sampling the forward wave and one the reflected wave — making it well suited for simultaneous incident and reflected power measurement without interrupting the main transmission line. Manufactured by Hewlett-Packard, the 774D is a rugged, compact inline device built to HP's precision RF component standards.

Specifications & What's Included

• Manufacturer: Hewlett-Packard (HP)
• Model: 774D
• Type: Dual Directional Coupler
• Frequency Range: 215–450 MHz
• Coupling: -20 dB (nominal across band, per label chart)
• Coupling flatness: approximately -18 to -22 dB across 200–500 MHz (per top-panel chart)
• Connector Type: N-Type (main line and coupled ports)
• Housing: Gray anodized aluminum, inline form factor
• Coupler only — no cables or adapters included

Applications

Dual directional couplers like the HP 774D are standard passive accessories in RF and microwave test setups. They are used to sample a small, calibrated fraction of the RF power flowing in both the forward and reverse directions on a transmission line — enabling simultaneous measurement of incident power, reflected power, and return loss without breaking the main signal path. The 215–450 MHz range covers the upper VHF and lower UHF spectrum, making this coupler relevant to communications testing, antenna matching, amplifier characterization, and general RF lab work in that band. HP's 774-series couplers were widely used alongside HP signal generators, spectrum analyzers, and network analyzers through the 1970s–1990s, and are still sought after for legacy bench setups and calibrated RF test systems. The -20 dB coupling factor provides a 1/100th power sample — a common ratio that keeps coupled port levels manageable for detector or power meter inputs while leaving the main line signal largely undisturbed.