DEMI L3-2ULNACK User guide

DEM L3-2ULNAK or CK

Noise Figure:

0.8 dB nominal

Gain:

22 dB nominal

Frequency Range:

10-10.5GHz

Input Voltage:

7 - 16 VDC

Current Drain:

<50 mA

Circuit board

Correct

Incorrect

Solder Fillet

Incorrect Component

Placement

10 GHz. PHEMT LNA amplifier Kit / Complete Kit ass embly guide

SPECIFICATIONS

Description:
The L3-2ULNAK or CK is a Kit or Complete Kit of our new L3-2ULNA 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 SMA connectors. The Kit version is
the PCB and components only. When completed, this 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 should 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, Q1and Q2. All other components are ESD resilient but are attached to
the circuitry which contains the active components.

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

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FIGURE 1.

with ohm meter. Next attach Q1and Q2. Follow the marking shown on the component
placement, align and solder the drain lead first (the output lead). 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 R5, R11 and U1. 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 C12-C14. It is indicated on the component placement guide.

When complete, check for missing solder, missing components, or shorts. Feel free to
use an ohmmeter for testing any conn ecti o n. To Test Q1a nd Q2 with a ohm meter, verify
that the drain lead is not shorted to the source. It should be between 3 and 15 ohms to
ground. Be sure to Zero your meter first. The gate should be in the Kilo-ohm region. Now
install U1 as shown
in Figure 2. U1 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 in
Figure 3. Then
install D2 if you
have a complete Kit.

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. 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

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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 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

R5 and R11 still not installed, the drain voltage will not be connected to Q1 and Q2 so voltage
may be applied to the feed through without endangering them.

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 R5 and R11 is to be assembled. If it is not there, find
the open circuit and repair. Now verify that the gate bias is functioning correctly. Measure
the Gate voltage on the Q1 and Q2. 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 R5 and R11

.

Final Testing:

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Install a 50 ohm load (of test equipment) to both input and output connectors. This

C1 1.0pF 50 mil ATC

C9 1000pF (0805)

IC1 7660 SMD

C2 1000pF (0805)

Q1 CE351K2

C11 1.0pF 50 mil ATC

Q1 CE351K2

R8 1K pot SMD

C4 1000pF (0805)

C6 1.0pF 50 mil ATC

R3 1K pot SMD

C7 1000pF (0805)

D1 MMBD914

U1 78L05

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

should be a good quality 10 GHz termination or test equipment. Apply the DC voltage to the
feed through connector and verify that the drain leads have voltage. It should be close to 2.0
VDC. Adjust R3 and R8 to obtain 2.0 VDC if not so. Now measure the drain current. This is
measured across R5 and R11 (220 and 240 ohm resistors with the use of Ohms law). The
drain current should be close to 10 -12 mA. If not check the values of R5 and R11. As the
gate voltage approaches 0VDC, the drain current will increase. If the gate voltage is adjusted
more negative, the drain current will decrease. The correct setting will yield Aprox 2.0VDC on
the drain with 10-1 2 m a of cur rent dr ain.

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 rather well but could be optimized for an additional 2 dB of gain with slightly better
Noise figure. If you desire to “Trim” the circuit to optimize, the stubs have additional pads to
be added or the subs may be trimmed or removed. Additional snow flaking on the output line
may produce additional gain. Also test with the Lid on. You may find interference in you test
environment. The lid may be installed with sealant after testing is complete if desired.

COMPONENT LIST

All resistors are 1206 size chips unless indicated. The white band is positive on the Tantalum
chip capacitors. All other capacitors are various sizes.

R6 51Ω (0805)

C10 0.1µF

R7 470 Ω

C3 0.1µF

C12 4.7 µF Tant R1 51Ω (0805) R9 12Ω (0805)

C5 0.1µF C13 4.7 µF Tant R2 470Ω R10 51Ω (0805)

C14 4.7 µF Tant

R11 220Ω

C15 0.1µF R4 51Ω (0805) R12 5.1KΩ

C8 0.1µF

R5 240 Ω

Hardware Parts List

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Component Placement

IC 1

+

L3-2ULNA SCHEMATIC

+

INP UT

OUTPUT

C1

D

R2

C3

R3

D1

C12

R1

C2

R12

R5

C15

C13

C6

S

G

Q1

8

2

4

5

3

R11

C14

C5

C11

U1

R9

R4

R6

D

S

G

Q2

R10

D C IN PU T

IN

OUT

C4

C7

R7

R8

C8

C9

+

C10

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