Narda 643

The Narda 643 is a precision standard gain horn antenna engineered for C-Band operation across 3.95 GHz to 5.85 GHz. It delivers 16.5 dB gain at mid-frequency with ±1.5 dB variation over the total band, making it suitable for RF and microwave measurement systems, antenna testing, and signal level calibration applications requiring accurate, predictable radiation characteristics.

– Technical Specifications

Frequency & Waveguide
• Frequency Range: 3.95 GHz to 5.85 GHz (C-Band)
• Waveguide Size: WR-187
• Input Flange: UG-407/U

Electrical Performance
• Gain (Mid Frequency): 16.5 dB (referenced to isotropic radiation)
• Gain Variation: ±1.5 dB over total band
• VSWR (Maximum): 1.15

Antenna Pattern
• Beamwidth (E-plane and H-plane): 23° at highest frequency, 34° at lowest frequency
• H-plane Side Lobes: >20 dB down
• E-plane Side Lobes: First at 13 dB down, second at 18 dB down, all others >20 dB down

Physical
• Weight: 2.3 lbs (1.1 kg)

– Key Features

• Controlled directional gain pattern across full C-Band span
• Low VSWR ensures minimal reflections at waveguide interface
• Predictable gain slope enables reliable signal level measurement and antenna characterization
• Frequency-dependent beamwidth behavior documented for pattern analysis

– Typical Applications

• Antenna gain reference standards
• RF power measurement and calibration
• Microwave system testing and alignment
• Signal source characterization in C-Band systems
• Waveguide-based measurement setups

– Compatibility & Integration

The 643 interfaces directly with WR-187 waveguide systems via UG-407/U flanges. Adapter components such as the 613A (Type N to WR-187) enable connection to external RF and microwave equipment, facilitating integration into mixed waveguide and coaxial measurement configurations.