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The Kanga Products FOXX-3 20m QRP Transceiver
Assembly Instructions
Stage 5: The power amplifier and filter.
In the FOXX series of transceivers the power amplifier (PA) transistor also functions as the receiver mixer. In the
FOXX and FOXX-2 the changeover was made with a switch. The FOXX-3 uses a relay to give semi-break-in keying. The
PA transistors collector is coupled to the antenna via a low pass filter. The base is driven by the crystal oscillator. The
emitter is connected by the relay to the volume control on receive and to the keyed +12v line on transmit.
Inductors L3, 4 and 5 are wound on toroid (ring) cores. L2 a ferrite bead, but the winding method is the same for
both types. L2 is wound with 14 turns of the thinner wire supplied in the stage 5 packet. The diagram on the
following page shows the appearance of a wound toroid. The number of turns on the coil equals the number of
times the wire passes through the central hole. In the case of L3, 4 and 5 using the thicker wire supplied, the turns
should be evenly spaced, not over lapping, with a gap between the first and last turn as shown. Wind these in the
direction shown so that the wires line up with the holes in the board.
When the winding is complete, trim the wires to a length of around 10mm measured from the edge of the toroid. To
tin the end of the wires, form a bead of molten solder on the tip of the soldering iron and pass the end of the wire
through it. After a few seconds the enamel will melt and the solder will wet the wire. Add more solder until the wire
is properly tinned. Avoid breathing in the fumes produced when soldering enamelled wire.
Solder all the components into place, press the heat sink onto TR6 and examine all solder joints before testing the
completed transceiver.
NOTE:
The BNC socket remains hot for a long time after soldering
.
Part Type
Markings
Notes
C26
100nF
104
C27
100nF
104
C28
180pF
180p
If possible, polystyrene capacitors
C29
390pF
390p
will be supplied for C28 to C31.
C30
390pF
390p
If they are not available, ceramic
C31
180pF
1800p
capacitors will be supplied instead.
TR6
2N2905A 2N2905A
L2
14 turns
Ferrite bead
Use the thinner wire for L2
L3
16 turns
Yellow Toroid
Use the thicker wire for L3, 4 and 5
L4
17 turns
Yellow Toroid
L5
16 turns
Yellow Toroid
CON4 Vertical BNC Socket
