WP-20 MODULE DESCRIPTIONS
NOISE SOURCE (See figure 6)
The noise source is a simple reverse bias junction
technique. 18 volts is applied to the emitter of Q1 through
R1. The base of Q1 is grounded. An avalanche effect is
produced since 18 volts exceeds the emitter to base break-
down voltage of Q1. The resulting white noise signal is
buffered by IC2C which has a gain of about 20. This out-
put is fed to the Filter/Mixer circuit. (More noise gain
can be achieved if necessary by changing R4 to 1meg)
POWER SUPPLY (See figure 7)
Two 9 volt batteries (preferably alkaline) in
series provide 18 volts to the noise source tran-
sistor. There is no need to switch it off because
current draw is only a few microamps. 9 volts from
B1 switched through S1 provides power to the rest
of the circuit. Average current draw of the en-
tire circuit is about 25ma. As B1 wears down the
A.D. Repeat function may not operate. When this
happens, just interchange B1 and B2.
Capacitors Cl, C4, C7 and Cl0 bypass to
ground any spikes from IC's in the circuit which
perform switching functions.
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