The Tektronix Type 191 Constant Amplitude Signal Generator is a precision sine wave source engineered for testing, calibration, and frequency-response measurements across 350 kHz to 100 MHz. Built around a Colpitts oscillator using 7119 dual triode vacuum tubes and hybrid transistor circuitry, it delivers stable, constant-amplitude output across its operating range and serves as a reliable calibrator for oscilloscopes and broadband device characterization.
Technical Specifications
Frequency Range: 350 kHz to 100 MHz in seven bands.
Output Amplitude: Adjustable in calibrated steps from 5 mV to 5 V peak-to-peak into a 50 Ω load. Maximum open-circuit voltage reaches approximately 11 V peak-to-peak.
Amplitude Accuracy (50 Ω load):
• 0.5–5 V range: ±3% of indicated amplitude
• 50–500 mV range: ±4% of indicated amplitude
• 5–50 mV range: ±5% of indicated amplitude
• At 50 kHz reference: ±2%
Amplitude Regulation: Less than ±3% variation from 50 kHz baseline across any frequency (5 mV to 5.5 V into 50 Ω or through ≤5 ns RG-8A/U cable). Between 42 MHz and 100 MHz, outputs of 5–55 mV exhibit variation less than +3% and −5%.
Oscillator Configuration: Colpitts topology, grounded cathode Class C with two 7119 tubes.
Power Supply: Unregulated 450 V internal supply. Selectable line input: 105, 115, 125, 210, 230, or 250 VAC. Fuses: 3AG, 0.4 A (slow-blow, 115 V) or 0.2 A (slow-blow, 230 V).
Warm-up Time: 5 minutes at 25°C ±5°C for specified accuracy.
Operating Temperature: 0°C to +50°C ambient.
– Key Features
• Seven-band frequency selection for precise tuning within 350 kHz–100 MHz window
• Three output ranges spanning millivolt to 5 V amplitude
• Aluminum-alloy chassis with anodized panel; glass laminated circuit boards
• 50 Ω optimized design; cable losses increase with RG-58A/U substitution at high frequencies
– Typical Applications
• Frequency-response testing of broadband RF and analog circuits
• Oscilloscope calibration and verification
• Signal source for receiver and amplifier characterization
– Compatibility & Integration
Output connector rated for 50 Ω coaxial loads. Amplitude regulation and accuracy specifications apply when terminated in 50 Ω or connected via short RG-8A/U cable runs.
