QRPKits DC20A, Manual

Page: 13 / 18

2/14/2007 Page - 13
Group 4: Low pass filter
When winding the toroid cores, remember that one pass of
wire through the center of the core is one turn. Also try to
keep the wire snug to the outside of the core.
T2 is a bifilar wound transformer. This simply means you wind
two wires on the core. Two colors of wire are used to help
identify which is which. You can twist the wires together, or
simply lay them side by side as you wind the turns.
Wind 6
turns of the wire pair. When you are done, there will be a
red/green pair at the start and finish of the windings. Reverse
the red and green wires on one side of the core, so that both
ends of the red and green wires are opposite each other on
the core, as shown in the diagram above. Now trim back the
leads and tin them. Insert the wires into the board with the red
wires in the holes marked B B’ and the green wires into the
holes marked A A’, then solder into place.
location value markings √
C24 (All) .1 uF 104 Mono
T2 (All) See notes
40M
C23 68 p 101 Mono
C30 330 p 331 Mono
C29 680 p 681 Mono
C28 330 p 331 Mono
L2 21 turns T37-2 (red)
L3 16 turns T37-2 (red)
30M
C23 68 p 68 Mono
C30 220 p 221 Mono
C29 560 p 561 Mono
C28 220 p 221 Mono
L2 14 turns T37-2 (RED)
L3 12 turns T37-2 (RED)
20M
C23 33 p 33 Mono
C30 150 p 151 Mono
C29 330 p 331 Mono
C28 150 p 151 Mono
L2 17 turns T37-6 (YEL)
L3 13 turns T37-6 (YEL)