SP-210 Detector

(from TM 11-866)

16. SECOND DETECTOR. -- The 2nd detector (V8) is a twin
diode operated with both plates and both cathodes connected in
parallel. Its IF input is obtained from the untuned secondary of
coil L32 in transformer T4 in the plate circuit of the 3rd IF ampli-
fier (V7). To facilitate operation of the LIMITER tube (V9) the
diode load resistance totaling 475,000 ohms is divided into two
approximately equal parts. One part, 250,000 ohms (R30), is placed
between the paralleled cathodes and ground and is by-passed (for
IF) by a 50 micromicrofarad capacitor (C26). The other part, totaling
225,000 ohms is between the low-potential end of the secondary and
ground, and is made up of 100,000 ohms (R48), 75,000 ohms (R24), and
50,000 ohms (R25). The 100,000 ohm resistor (R48), together with
two 50 micromicrofarad capacitors (C44, C45), constitute a filter to
prevent IF voltages from reaching the 50,000 ohm resistor (R25) and
the AUDIO GAIN control (R26).