Elecraft K2 Owner's Manual - Manual (Page 55)

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LECRAFT ®
Solder C91 (.001 µF, "102") to the two pads shown in Figure 6-
14c. Use short leads.
Solder C88 (68 pF, "68" or "680") between pins 12 and 13 of U4
as shown above. Use short leads.
Locate the 100 µH RF choke, RFC15 (brown-black-brown). This
choke may be the same size, or nearly so, as the other chokes. When
installing adjust the leads to reach the pads shown in Figure 6-14c.
Solder RFC15 to the pads indicated above. Use short leads.
Examine C88, C91 and RFC15 closely. Their leads should not
contact adjacent pads or traces.
Locate the crystals used on the RF board: 12.096 MHz (1),
4.9152 MHz for BFO (2) and 4.9136 MHz for crystal filters (7).
Do not mix the BFO and filter crystals, which have different
characteristics.
The bag of 7 filter crystals should have a number written on it.
Record the number here: ___________. (This identifies the tested
frequency of the crystals, and can be used in aligning filters.)
Install the 12.096 MHz crystal, X1, at the lower left. The crystal
should be seated flat on the board before soldering (it is OK to bend
the pins to hold it to the board). X2 is not used.
To the left of X1 (along the edge of the board) you’ll find a pad
for grounding the crystal case. Use short lengths of bare wire to
ground the crystal on at the top of the can.
Install the BFO crystals at X3 and X4 (near J7). Important: trim
X3's leads, and fold them down flat against their pads, before
soldering. Then use a minimal amount of solder. This is necessary to
avoid interference between X3 and L33 in a later step.
Ground the cases of X3 and X4. The ground pads are to the left of
the crystals.
Install the 4.9136 MHz filter crystals at X5 through X11.
Ground the cases of X5 and X6. The ground pads are near where
the two crystals meet.
A special grounding technique is required for X7-X11. There
are two ground pads for each of these crystals, one on either side. Use
bare wires (10 total) for grounding the crystals as you did in previous
steps, but do not solder the wires to the tops of the crystals. The wires
must be soldered to the sides of the crystals, instead, about 1/4" (6
mm) up from the surface of the PC board.
Be very careful not to overheat the crystals. Use a temperature-
controlled iron, and limit soldering time to about 3 seconds per
soldering attempt.
i
In the following steps you’ll install several toroidal inductors.
Use the number of turns indicated. Do not attempt to alter the turns
to match inductances specified in the parts list.
Sort the black and dark gray toroidal cores into three groups to
avoid mis-identifying them in later steps. You should have eight FT37-
43 ferrite cores (3/8", 9.5 mm); four T44-10 iron powder cores (0.44",
11 mm); and one FT50-43 ferrite core (0.5", 12.7 mm). Ferrite cores
are dark gray; T44-10 cores are black.
Locate a 3/8" (9.5 mm) diameter ferrite toroidal core (type FT37-
43) as described above.