Elecraft K1 - Manual (Page 33)

32
E
LECRAFT
Locate the dark gray (ferrite) toroid cores. You should have
four smaller cores (type FT37-43) and one larger core (FT50-43).
The three inductors to be wound in the following steps, L2, T1, and
T2, all use the smaller ferrite cores.
i
Review the toroid winding and lead preparation instructions
if necessary (page 14).
Wind L2 using 16 turns of red enamel wire (11 inches, 28 cm).
L2 should appear similar to Figure 4-3, on page 14 (the figure
shows 14 turns rather than 16). Recall that each pass of the wire
through the core counts as one turn.
Prepare L2's leads as before (page 14). Remove the insulation
to within about 1/8" (3 mm) of the core, then tin the leads.
Install L2 vertically, at the back edge of the RF board between
the on-off switch (S1) and the antenna jack (J5).
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T1 is a toroidal transformer, with two numbered windings.
These numbers are printed next to each pad on the PC board. T1's
windings are 1-2 and 3-4.
T1 is wound on an FT37-43 ferrite core (dark gray) and has
windings similar to those shown in Figure 6-8a. Wind the 3-4
winding first, using 20 turns of red enamel wire (13", 33 cm). This
winding should occupy 80 to 90% of the core. Note: the drawing
shows only 14 turns.
Wind the 1-2 winding on top of the 3-4 winding, using 4 turns
of green enamel wire (6", 16 cm). These turns should be wound
tightly, and will overlap the turns of the first winding. (The drawing
shows the turns interleaved, for clarity, but this is not required.)
Strip and tin all four of T1's leads carefully.
Install T1 flat against the board, between U1 and U2. Insert
the leads into its numbered holes as shown by the component
outline. Pull the leads taut on the bottom, then solder and trim.
1, GRN
4, RED
3, RED
2, GRN
4, RED
1, GRN
2, GRN
3, RED
(a) T1 (b) T2
Figure 6-8
T2 is wound on the same core type as T1. Start with the
3–4 winding, which uses 20 turns of red enamel wire (13", 33 cm).
The 1-2 winding uses 5 turns of green enamel wire (6", 16 cm).
Strip and tin T2's leads.
Install T2 flat against the board, to the right of U2. Pull the
leads taut, then solder.
Using your DMM, check for continuity between the pads of
L2. If the DMM doesn't indicate a short (< 5 ohms), you may not
have fully removed the insulation from one or both leads. Since the
insulation can be heat-stripped, you can usually improve the
electrical connection by re-heating each lead for 4 to 5 seconds.
Similarly, check T1’s two windings (1-2 and 3-4) for
continuity. Then check T2's windings.
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Toroidal inductor L1 (VFO) will not be installed until the
VFO is aligned in Alignment and Test Part I (page 36).