Rohde and Schwarz DDF255 Digital Direction Finder

The Rohde & Schwarz DDF255 Digital Direction Finder is a wideband signal localization system engineered for spectrum monitoring, interference hunting, and security operations. It employs correlative interferometer direction finding methodology to deliver high-accuracy bearings across VHF/UHF/SHF bands, with system bearing fluctuation of 2° rms. The instrument integrates the R&S ESMD monitoring receiver and supports realtime bandwidth processing up to 20 MHz (80 MHz with option), enabling rapid signal acquisition across its frequency range. Scan speeds reach 100 GHz/s. Hardware-accelerated multichannel signal processing and multichannel digital downconversion are available via optional boards.

– Technical Specifications

Frequency Coverage
• Base unit: 20 MHz to 3.6 GHz (DF mode to 3 GHz)
• With DDF255-HF option: 9 kHz to 3.6 GHz (DF mode 300 kHz to 3 GHz)
• With DDF255-SHF option: 20 MHz to 26.5 GHz (DF mode to 6 GHz)
• Combined options: 9 kHz to 26.5 GHz (DF mode 300 kHz to 6 GHz)

Direction Finding Performance
• Method: Correlative interferometer
• Bearing accuracy: 2° rms (VHF/UHF/SHF); 5° rms below 1 MHz with 250 Hz bandwidth and 5 s averaging
• Sensitivity: 10 µV/m to 4 µV/m (below 1 MHz)
• Polarization: Watson-Watt, vertical

Signal Processing
• Realtime bandwidth: 20 MHz standard; 80 MHz optional
• Scan rate: Up to 100 GHz/s
• DF antenna inputs: 4
• Monitoring antenna inputs: 2 HF (N-female, 50 Ω), 2 VHF/UHF (N-female, 50 Ω)
• IF2 output: 405.4 MHz

Power & Interface
• Supply: 10 V to 32 V DC, 1.0 A to 3.3 A
• Consumption: 16 V to 20 W typical
• External reference: 10 MHz, 0 dBm to 10 dBm
• USB: Two ports for peripherals
• Additional: GPS, compass, serial, trigger interfaces

– Key Features

• High-density integration for stationary and mobile deployment
• Class A DF accuracy per ITU recommendations
• Optional wideband processing to 80 MHz realtime bandwidth
• Multichannel signal extraction via digital downconversion
• Dual HF and VHF/UHF antenna paths

– Typical Applications

• Spectrum monitoring and interference location
• Security and signal intelligence operations
• Mobile and fixed surveillance systems

– Compatibility & Integration

The system accepts external 10 MHz references at 0 dBm to 10 dBm and integrates GPS, compass, and serial trigger inputs for synchronized operations. USB connectivity supports external recording and peripheral control.