Solid State Shortwave Receivers For Beginners - The Listeners Guide

Components List for Fig.20
Resistors (all ¼ watt 5%).
R1 680 ohms R5 680 ohms
R2 1k R6 2.2 Meg.
R3 47k R7 5.6k
R4 1k
VR1 10k lin. carbon.
Capacitors.
C1 100nf plastic foil.
C2 100nf plastic foil.
C3 5.6nf ceramic.
C4 100nf plastic foil.
C5 5.6nf ceramic.
C6 5.6nf ceramic.
C7 4mfd. 10v.w.
C8 100mfd. 10v.w.
VC1 365pf air spaced (type 0).
VC2 50pf air spaced (type C804).
Semiconductors.
Tr1 2N3819.
Tr2 3N140 or 40673.
Tr3 BC109.
D1 OA90.
Inductors.
T1 Denco Green D.P. coils Ranges 3, 4, and 5.
L1 10mH. (Repanco CH4).
Miscellaneous.
S1 S.P.S.T. toggle switch.
Chassis and panel, sockets, 9V. battery, etc.
in operation to a JUGFET. It does, however, have an even higher
input impedance, this being something in the region of 100,000 Meg
ohms.
Tr2 is used as a regenerative R.F. amplifier and it has L1 as its
drain load. The method of obtaining regeneration, and coupling the
input signal to the device is the same as in the three previous designs.
So is the method of basing the FET.
The gain of a dual gate MOSFET is controlled by the voltage at
its gate 2 terminal. Gain is at maximum with the g2 terminal biased
slightly positive of the source terminal. Reducing the g2 bias causes a
reduction in gain.
R3 and VR1 form a potential divider across the supply lines and
the g2 terminal of Tr2 is fed from the slider of VR1. When VR1 slider
is set towards the top of its track, the gain of Tr2 is at about maximum.
When it is set towards the bottom of the track, gain is at around minimum.
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