The coils are wound as described for Figure 9, and alignment of the two tuned circuits is also carried as described there. L1 has five turns, and L4 four turns, situated as explained for Figure 9.
TR1 operates with fixed gain. If a gain or sensitivity control is wanted, this can be added as shown in other circuits. An aerial input potentiometer may be added (Figure 7) or gate 2 voltage can be adjusted by a potentiometer
A gain control is not likely to be necessary when the stage is used before a receiver which has its own RF gain control. Otherwise, overloading of early stages of the receiver may arise with strong signals.
Alternative forms of output coupling are shown. If L4 is used, one end is grounded (see Figure 9) and Y is connected to the aerial input socket of the receiver. This method is preferred where the receiver has the usual medium or low impedance input. Some receiver have a high impedance aerial socket for end fed and similar aerials which are arranged for high impedance feed, and with these results will be improved by not using L4, instead, C4 provides capacity coupling to the aerial socket at X. Trimming and alignment of L2 and L3 should be checked after adding this connection and C4.
The 40602 or 40673 will perform well here, though other dual gate FETs can be fitted with satisfactory results.
Segregation of circuits is most easily achieved by using a small metal chassis, with L1/L2 on top, near VC1/2. A lead can then pass down through the chassis from VC1 to G1. TR1 and associated
items, including L3/L4, can be under the chassis. This screens L3 from L2. The RF connection from X or Y to the receiver should be short, and away from the aerial lead to L1.
