©1995 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 10/23/02
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with solder as long as the three
leads are all soldered at the top.
e. Solder metal shield to ground
plane on top of pc board in position
shown in figure 2. Keep the shield
as close as possible to the transistor
to leave room for output coil L2.
First, tack solder the shield to the
board at each end. Once the shield
is aligned properly, run a bead of sol-
der the whole length of the shield.
Then, run a second bead of solder on
the other side of the shield. Solder-
ing on both sides of the shield pr o-
vides maximum mechanical support
for the shield.
f. Install output coil L2 in the po-
sition shown. Form the lead to be
soldered to the pc board so the coil
fits within the edges of the board.
Insert the other lead in the center of
ft cap C8. Solder both leads of L2.
g. Install C1, C2, and C3, keeping
leads short as possible. C2 should
have the rounded end to ground.
h. Install C7 and U1 in the holes
shown. The leads of C7 must be
formed to the narrower spacing of the
pads on the board.
i. Turn the preamp over, and ori-
ent it as shown in figure 3. Position
ferrite bead Z1 as shown. Note that
positioning the body of the bead
against the feedthrough capacitor
prevents its leads from shorting to
anything. Solder one lead to the in-
side metalization of ft cap C8, and
tack solder the other lead to the pad
for the left-hand lead of U1 as
shown. If there already is solder on
the bottom of C8, melt it and slide
the lead in.
j. Using #22 bus wire supplied
and the shank of a 1/8 inch drill bit
as a tool, wind coil L1 as shown. (It
doesn't matter which direction you
wind.) Consult the parts list for the
correct number of turns. Count com-
plete turns, from bottom to bottom.
For reference, the sample in figure 3
shows 5 turns.
After winding, use a knife to sepa-
rate the turns so they are not short-
ing together. The turns should be
barely spaced apart, just enough to
prevent shorting. Then, form the
ends of the leads so that the wire
coming off the bottom of the coil is
bent to go directly over to the holes
in the board. The bottom of the coil
should be 1/16 inch from the surface
of the board.
Be sure that the coil leads are in-
stalled in the correct holes: the one on the
left should connect to the junction of C1,
C2, and gate 1 of the transistor; the one
on the right should connect to the ground
plane.
Then, solder both leads.
k. This completes construction.
Look over all components and solder
connections. Check for shorts or
parts in the wrong places.
INSTALLATION.
The preamp can be mounted to
any flat surface. Simply drill two 1/8
inch holes 1-7/16 inch apart, and at-
tach the preamp with the 4-40
screws and standoffs or spacers as
desired.
Complete shielding of the preamp
is not required. However, some care
should be given to selection of the
mounting location with regard to
feedback from adjacent receiver cir-
cuits or rf pickup if mounted very
close to a transmitter circuit. Be-
cause the unit is small, make sure
that it isn't installed tight against
the rf ampl ifier or first mixer of the
receiver to minimize feedback ef-
fects.
Connect the input and output ter-
minals in the receive signal path
with miniature coax, such as RG-
174/u, as shown in figure 2. Be sure
to keep the stripped pigtails as short
as possible to maintain a 50
Ω
path.
Connections are made by inserting
the stripped ends of the pigtails into
the pads on the board and soldering.
Normally, the preamp is mounted in
some sort of enclosure with UHF or
similar connectors on the enclosure
and miniature coax installed be-
tween the preamp and the large coax
connectors. In some cases, the out-
put of the preamp can go directly to
the receiver with the miniature coax.
L
Caution: Don't connect the preamp
in the transmit signal path.
Connect power supply lead to E5.
The LNW requires fi10 to 15
Vdc. Current drain is about 10 mA.
Caution is advised in selecting a
power source. Solid state amplifiers
can be damaged by large voltage
transients and reverse polarity. Al-
Figure 2. Top View of LNW Board
E1
E2
C2
C1
C3
LONG DRAIN LEAD
SHIELD
C8
L2
Q1
R1
R2
U1
C7
GATE 2
SOURCE
GATE 1
E3
E4
E5
RF OUTPUT
COAX
RF INPUT
COAX
POWER
C5
Figure 3. Bottom View of LNW Board
Z1
L1
C8
C5
U1