Solid State Shortwave Receivers For Beginners - The Listeners Guide

Components List for Fig. 18
Resistors (¼ watt 5%).
R1 1k R5 220 ohms
R2 1k R6 220k
R3 8.2 Meg. R7 390 ohms
R4 5.6k R8 6.8k
VR1 10k log, carbon.
Capacitors.
C1 100mfd. 10v.w.
C2 10nf plastic foil.
C3 4.7nf ceramic.
C4 5.6nf plastic foil.
C5 10mfd. 10v.w. -
C6 100nf plastic foil.
C7 10nf ceramic.
C8 470nf plastic foil.
C9 470nf plastic foil.
C10 100mfd. 10v.w.
C11 100mfd. 10v.w.
VC1 50pf air spaced (C804).
VC2 365pf air spaced (type 0).
Semiconductors.
Tr1 2N3819.
Tr2 BC109.
Tr3 BC109.
D1 OA90.
Inductors.
T1 Denco Green D.P. coils Ranges 3, 4, and 5.
L1 10mH. (Repanco CH4).
Miscellaneous.
High impedance speaker. S.P.S.T. toggle switch (S1).
Chassis, panel, battery, etc.
Fig.18 shows the complete circuit diagram of the reflexive
receiver. The wiring to T1 has much in common with the previous circuit,
the main difference being that R8 and C2 have been included in the earthy
side of the tuned winding of T1. At R.F. these do not have any significant
effect as C2 provides a low impedance path to earth for R.F. signals.
Neither is the D.C. biasing noticeably affected since RB provides a suitable
path for the minute gate bias current for Tr1.
L1 forms the R.F. load for Tr1, and R1 and C5 - C1 in series form
an R.F. decoupling network which feed the positive suplly to the R.F.
amplifier circuit. The R.F. output from Tr1 drain is coupled by way of
C4 to the detector diode, D1. R8 now acts as the load resistor for D1
and C2 is the R.F. filter capacitor.
The audio signal developed across R8 is fed via the tuned winding
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