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trim to excactly -15V/15V by usage of the Powersupply Multiturn trimmer, measure between -V and 0 and +V and 0
use a 12V - 24DC powersupply at the input.
Ring modulator
Positive Null
01) Put switch in DC position
02) Raise VCO 1 slider only
03) Monitor output with oscilloscope and adjust POS NULL for minimum output
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