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660_AND_1000_Hz_FOR_SSB_TESTING

2014-11-19 23:04  
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660_AND_1000_Hz_FOR_SSB_TESTING
Produces two audio frequencies with all harmonics and cross products down 40 dB or more, as required for accurate testing of amateur SSB equipment. Two sections of Raytheon 4136D quad opamp serve as Wien-bridge audio oscillators, one at 1000 Hz and one at 660 Hz. Silicon signal diodes in each bridge act as nonlinear stabilization elements. Third section of opamp adds sine waves, and fourth section is simple inverter with gain of n for push-pull or balanced output. With all four pots at midvalue, adjust R2 for 12 V P-P at TP2 and adjust R4 for 12 V P-P at TP2. Open X2 and adjust R3 to give 12 V P-P from either output terminal to ground, then close X2 and repeat for X1 and R4. Output should now be 660 and 1000 Hz added linearly as required, with no cross-products. Use regulated ±15 V supply.-H. Olson, A One-Chip, Two Tone Generator, CQ, April 1974, p 48-49.