DEM L13ULNAK or CK
Noise Figure:
< 0.6 dB
Gain:
> 16 dB
Frequency Range:
2300-2450 MHz
Input Voltage:
7 - 16 VDC
Circuit board
Correct
Incorrect
Solder Fillet
Incorrect Component
Placement
2.3-2.45 GHz. P HEMT LNA am plifier Kit / Complete Kit assembly guide
SPECIFICATIONS
Description:
The L13ULNAK or CK is a Kit or Complete Kit of our L13ULNA low noise amplifier
designed by W5LUA and Down East Microwave Inc. The complete kit comes with a
machined electro plated enclosure, the PC board kit, and connectors of choice (SMA or “N”).
The Kit version is the PCB and components only. The LNA may be installed anywhere in your
system but it is a receive only preamplifier and requires coaxial relay switching for transceive
operation.
Before starting assembly, read through the entire assembly guide. Review all of the
assembly and test procedures and inventory the components. If you have the CK, sort the
hardware and trial fit any of the hardware if a screw or connector hole looks questionable.
When you are sure of all of the kit contents begin the assembly with confidence and have fun!
Begin Assembly:
The document assumes that the complete kit version is being assembled. If you have
the board kit only, use only what pertains to its assembly.
Start by fitting the circuit board into the enclosure. The board s hould drop in and fall
out when flipped upside down. If it “Sticks”, sometimes the corners of the board are not cut
correctly or have excess material left over from the machine cut. Simply trim to fit. When in
place, the 5 mounting holes s houl d line up. The RF connector pin holes should also center on
the input and output RF circuit traces
The board assembly is easy but follow standard ESD precautions when handling
components. Use a grounded solder iron if possible. Be sure you are discharged of static
before handling IC1 or Q1. All other components are ESD resilient but are attached to the
circuitry which contains IC1 and Q1.
After reviewing Figure 1 and referring to the comp onent placement diagram and the
components list, begin to assemble the PCB by installing IC1 first. Pin 1 is marked on the
placement diagram. Solder pin 3 first. This is the ground pin. Check for alignment of the
other pins and if OK, proceed to solder the other 7 pins in any order. Check for solder shorts
with ohm meter. Next attach Q1. The leads of Q1 may be “Pre” solder tinned. Follow the
/Kits/L13ULNACK.doc 1 Rev. A 3/9/2021
FIGURE 1.
marking shown on the component placement, align and solder the drain lead first (the ou tput
lead or the lead connected to R1). Check the alignment and then solder the source leads
(the 2 leads on the ground plane with the via holes). You may find the source leads difficult
to solder because the heat from the iron is sunk away through the via holes to the ground
plane. Solder the gate lead last. Install all other components on the circuit board in any order
except R1, C4, and VR1. All ground connections have multiple ground vias and may be
difficult to solder. Solder multiple connection pads last. Be sure to check the polarity of C4,
C5, and C6. It is indicated on the component placement guide. Lastly, install the L1 Inductor
using a 0.400” length of a single strand of wire that is supplied. Save the surplus. See figure
2.
When the component installation is complete, notice that DC bias choke may be
touching the mounting hole. If you do not require DC bias through the coax, simply cut the
choke from the RF trace. If you plan on using it, shorten the middle with a wire jumper. Use
the same wire strand as on the input inductor. Feel free to use a ohm meter for testing any
connection. To Test Q1 with a ohm meter, verify that the drain lead is not shorted to the
source. It should be
between 6 and 15
ohms to ground. Be
sure to Zero your
meter first. The gate
should be in the
Kilo-ohm region.
Now install VR1 as
shown in figure 2.
VR1 is installed by
cutting the leads
short and soldering
them to the circuit
laying flat with the
labeling facing up.
Then after soldering,
bend the package
up to depict the
component
placement
document or as
seen in Figure 2.
FIGURE 2.
Hardware Assembly:
The mechanical fit is very important to the function of this LNA. This is the reason for trail
fitting the board before assembly. Trimming the PC board now would crack some installed
components. BUT—some solder may have wicked through the plated through vias. The bottom of
the board needs to be flat. You can solder wick any excess solder or file smooth with a small fine
file. Just be sure the bottom is flat!
The board again should drop in the enclosure and line up with the mounting holes. Mount
the board with the 3-48 Phillister head screws. Then install C4. It is a very awkward fit but it will
/Kits/L13ULNACK.doc 2 Rev. A 3/9/2021
work. Be sure of the polarity (See Fig 3). Next install the RF connectors first by cutting the Teflon
back to 0.200” total length with the center pin extending 0.050” more . Be sure to file any sharp
edge off of the center pin after cutting. OR—you can eyeball the lengths using the enclosure wall
as a guide. Insert both RF connectors in the holes on the enclosure being careful that the center
pin does not catch the circuit board on the way in. The pin should rest on top of the circuit. Be
sure that the connector flange is flush with the enclosure. If not, the Teflon is too long. Re-trim if
needed. After fitting, if you require weatherproofing, you may apply a sealant before bolting the
connectors in place with the 4-40 x 1/4” screws.
Warning: Do not
tighten any board
or connector
screws after the
center pins are
soldered! This
may tear the
center pin from the
circuit board. Be
sure that all screw
are absolutely tight
before soldering!
Solder the two
center pins when
ready. They should
be on center of the
circuit board trace.
FIGURE 3.
Install the 8-32 Feed-thru connector and ground lug (see Figure 3) in the remaining hole
of the enclosure. Again if you want a weatherproof enclosure, apply some sealant to the
connector before installing. Connect the 1N914 type diode between the DC feed-thru connector
and the point on the component placement labeled “+DC Input”. This is a reverse polarity
protection diode.
Pre-Testing and Final Assembly:
Preliminary testing is required before final assembly and testing the RF circuit. With
R1 still not installed, the drain and gate voltage will not be connected to Q1 so voltage may
be applied to the feed through without endangering Q1.
Apply a DC input of +7 to +17 VDC to the feed through connector and ground lug.
Measure +5VDC on the output side of VR1. Verify that the +5VDC travels through the drain
circuit biasing to the Junction of where R1 is to be assembled. If it is not there, find the open
/Kits/L13ULNACK.doc 3 Rev. A 3/9/2021
circuit and repair. Now verify that the gate bias is functioning correctly. Measure the voltage
C1 0.1µF (0805)
C7 0.1µF (0805)
IC1 7660 SMD
R4 51 (0805)
C2 8.2 pF ATC
C8 8.2 pF ATC
L1 0.4” Strand
R5 1K pot
C3 0.1µF (0805)
C9 8.2 pF ATC
Q1 NE3210
R6 100
C4 10.0 µF
C10 8.2 pF ATC
R1 15
VR1 78L05
C5 1.0 µF
CR3 MMBD914
R2 51 (0805)
PC Board
C6 10.0 µF
CR4 MMBD914
R3 5.1K
1 - Enclosure and Lid
12 - 4-40 x 1/4” screws
2 - RF connectors (SMA or “N”)
5 - 3-48 x 3/16” Fillister head
1 - #8 ground lug
1 - 1N914 type diode
1 - #8-32 feed-thru connector
on the Q1 side of C2. It should be less than -0.8VDC (Negative voltage). Adjust R5 to obtain
-0.4VDC. Again if any of the voltages can not be obtained, trace the circuit for problems.
There should be -5 VDC on pin 5 of IC1. If it checks out, remove the DC voltage from the
LNA and install R1.
Final Testing:
Install a 50 ohm load to both input and output connectors or your 50 Ohm gain
measuring equipment. This can be a termination, an antenna, or a receiver. Apply the DC
voltage to the feed through connector and verify that the drain lead has voltage. It should be
between 2 and 5 volts DC. Now measure the drain current. This is either measured across
R6 (100 ohm resistor with the use of Ohms law) or may be measured directly on the +DC
supply line. The drain current should be between 15 and 20 mA. The drain current can now
be adjusted by varying R5. As the gate voltage approaches 0VDC, the drain current will
increase. If the gate voltage is adjusted more negative, the drain current will decrease.
Adjust R5 for approximatel y 20-25 mA of drain current.
If the DC testing is correct, the LNA will be operating correctly and the RF adjustments
should not be attempted unless you have a way of measuring Gain and/or Noise Figure. Just
re-test the DC current drain to ensure proper operation. Even if you do have the equipment
available, there will only be minimal adjustments, if any, to be made to improve the
performance of the LNA. If it is assembled correctly and the bias is set correctly, the LNA will
perform correctly rather well.
If you desire to “Trim” the circuit to optimize, the trace directly connected to the Gate of
Q1 can be made narrower to improve the NF. The stub after R1 may be adjusted for
improved gain. Also test with the Lid on.
The lid may be installed with sealant after testing is complete if desired.
Component List
All resistors are 1206 size chips. The white band is positive on the Tantalum chip capacitors.
All other capacitors are various sizes.
Hardware Parts List
/Kits/L13ULNACK.doc 4 Rev. A 3/9/2021
C2
C3
Cr4
C10
C8
C7
C1
C5
C6
C4
Q1
R2
R3
R4
R1
+
+
+
Vr1
DC INPUT
Cr3
C9
L1
Cut when
Required
LMC76
60
K
IC 1
+
13ULNA SCHEMATIC
+
+
INP UT
OUTPUT
DC IN PU T
VR 1
C2
L1
D
R1
R2
C3
R5
Cr4
C4
R3
C5
CR3
C10
R6
R4
C7
C8
C6
C9
S
G
Q1
C1
IN
OUT
8
24
5
3
1N4000
DC IN PU T
Component Placement
/Kits/L13ULNACK.doc 5 Rev. A 3/9/2021
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