DEM Part Number 1296-144 PCB, K and CK
23 cm Transverter PCB, Board Kit, and Complete Kit
Specifications
Frequency range: 1296 MHz. = 144 MHz.
Noise Figure and Gain: <1.5 dB NF, > 17 dB Gain with >+5dBm IP3 Input
Power Output: 3 watts. Lower levels with different configurations
TXIF Drive level: 1 mW to 10 Watts maximum dependant on IF configuration.
DC Power requirements: 13.8 VDC nominal. 11 to 16.5 VDC operational.
DC Current drain: 500 mA to 2.5 Amps depending on output power level.
Operational Overview
The DEM 1296-144 is a 23 cm to 144 MHz transmit and receive converter. It has a linear
output power of approximately 3 watts and may be achieved with as little as 10 mW or a maximum
of 10 W of IF drive with the correct IF configuration. The highlight of this transverter is the receive
section. The design uses a PHEMT that has a high-pass tuned input circuit biased for High IP3
output performance. It is followed by two 3 pole helical filters, a high output IP3 MMIC gain stage,
and a high level mixer with a IP3 output of +30 dBm. This design provides a sensitive low noise
receiver with superior out of band signal rejection that will tolerate IP3 input signals > +5 dBm!
Other improvements over the previous versions of 1296 transverters are in the Local Oscillator and
TX section. The base oscillator of the local oscillator circuit is housed in a shielded enclosure on
the circuit board. This shield coupled with the higher frequency base oscillator operation, (192
MHz), reduces the amount of spurious output while providing greater temperature stability. The
transmit section has improved filtering to eliminate all other spurious emissions. The DEM 1296144 has a built in transmit / receive relay on the RF side with provisions for external switching for
adding a high power amplifier or preamplifier to your 23 cm system. The 144 MHz IF levels and
options are adjustable on both transmit and receive with a dynamic range of approx. 25 dB. This is
useful for adjusting your maximum output power and setting the "S" meter level on your IF
receiver. The IF connections are via BNC connectors. Options have been provided for a key line
input PTT-H (+1 to 15 VDC) or PTT-L (a closure to ground) and auxiliary contacts on either
transmit or receive with a common line for many applications. The control, power, and auxiliary
connections are via RCA jacks. The 23 cm connectors are Type 'N' or SMA if separate TX and RX
ports are chosen. The 1296-144 is housed in our standard 4.125" x 1.875" x 7.75" extruded
aluminum enclosure that matches all of our other microwave transverters.
General Information
The detailed technical design information is posted in the library section of the Down East
Microwave Web site. The paper stresses the receiver’s immunity to out of band signals and
covers the design stage by stage. The 1296-144 kits and PCB are supplied with a schematic and
component placement diagram. The PCB is made of 0.062” thick Fiberglass G10 material. It has
plated 1 oz. copper with plated through ground Vias and will only require a general understanding
of the circuit design accompanied by good construction practices to produce a great working
transverter. The circuit board alone may be assembled and used in many different configurations.
It is perfect for the experimenter in the 23 cm band and requires very little microwave expertise.
The PCB by itself doesn’t require external mechanical support but will require a special
mounting technique. Down East Microwave will guaranty the performance of our circuit board
with your configuration but will not repair any transverters built from the 1296-144PCB unless
/Kits/1296-144CK.doc 1 Rev. B 9/20/2007
all components used are specified on the component list that accompanies the PCB when
purchased!
For a higher probability of success, and 100% support of Down East Microwave Inc., we
recommend at the minimum, using the 1296-144K. The K (kit version) includes the PCB and all
components required to produce a low transmit level 23 cm transverter. If higher output power is
required, you may simply order the hybrid power module that the circuit was designed for but
physical mounting may be difficult due to components located on both sides of the circuit board.
For this reason, if you wish a 3 Watt unit, we recommend using the complete kit version. The
1296-144CK (complete kit) includes the board kit and the hybrid power module along with all the
necessary hardware, connectors and enclosure. Also included in the CK is a special mounting
plate that allows the mounting of the assembled PCB and hybrid module into the enclosure
provided. The circuit board mounting plate is machined so that the helical filters, PCB, local
oscillator shield, the hybrid power module, and all external DC and RF connectors are mounted
together as a complete assembly before installing in to the enclosure. This plate is the key to the
maximum reliability of the transverter (heat transfer and spurious oscillations) and allows complete
alignment before final assembly into the enclosure.
Circuit Description
A local oscillator of 192.00 MHz is multiplied X 6, filtered, and amplified to the +17 dBm level
then is injected into a high level mixer. In receive, the 23 cm signal enters through either the RX
port or the common antenna port. It is amplified by a high level, tuned input PHEMT low noise
amplifier that has approximately 16-17 dB of gain with <1.0 dB noise figure. The input circuit is
designed to attenuate all signals out side of the desired 23 CM band. The amplified signal then
passes through a 3 pole helical filter that allows approximately 30 MHz. of amplified bandwidth.
This signal is then amplified by a high level MMIC before being filtered by the next 3 pole helical
filter that restricts the receivers operation to a narrow segment of the 23 CM amateur band. This
signal enters the high level mixer and exits the IF port passing through a VHF low pass filter and
optional IF gain stage with a variable attenuator. Then depending on the configuration, it will pass
through the IF switch or not before becoming available to the 28 MHz. receiver.
On transmit, it is a reverse process. The 2 meter transceiver applies a signal of up to 10
watts of drive and it is then attenuated and filtered before entering into the mixer. The 23 cm
transmit signal then exits the mixer and is filtered by the 3 pole helical before being passed through
the transmit gain stages. It is then amplified up to approximately +15 dBm before it is filtered again
to narrow the pass band energy. At this point the signal can be used as is or be amplified up to the
3 watt level before either exiting the TX port or the common antenna port.
Other LO input, RF and IF frequency schemes may be used with the 1296 transverter such
as our other 28 MHz IF versions or the 1268/9 transmit converters. Simply do the math. There are
a few limiting factors for different frequencies of operation. The IF will operate on any frequency
between 28 and 188 MHz. With the correct LO filters. The RF filters will cover the whole 23 cm
band. The LO filters in this kit will not tune to a 28 MHz IF range. All filters included in the kit may
need to be re-tuned or replaced and the levels will need to be checked. Therefore, if attempting a
large frequency change or using an odd IF frequency, is not recommended unless you have a
known signal source and a spectrum analyzer to determine your desired outcome of the
transverter.
For a more detailed circuit description about any component or circuit in particular, or if you
have questions about a desired scheme, we recommend you contact Down East Microwave before
proceeding with a modification to the kit.
/Kits/1296-144CK.doc 2 Rev. B 9/20/2007
s
Assembly Tips
It is recommended to read the entire document before you begin to assemble the kit, but the
following few paragraphs is a compilation of assembly techniques used and required to assemble
this kit. These various assemble techniques will be used for more than one component and may
determine the outcome of this kit. Review the examples shown and become familiar with the
components described in the text.
Soldering surface mounted active components
The dots or angle cut leads on the MMICs IC1-IC3, IC5-IC7 are as shown on the
component placement diagram and determine their correct orientation. IC10 is a 3 leaded
package with a solder tab. Its orientation is shown on the component placement diagram. The
MMIC’s must be positioned correctly prior to soldering. Removing a MMIC without damage is
difficult. The PHEMT Q3 has a wide lead for one of the source leads. (See figure 1B) Leads on all
active surface mounted components should be somewhat flat against the mounting surface, if they
are not, a small tool such as a small bladed screw driver can be used to flatten them before
attempting to solder (See Figure 2). After verifying that the leads are flat to the surface, you will be
ready to solder.
1. To begin to solder, pick one pad on the circuit board that you wish to attach the active
device to. Without the component in place, heat one side of the mounting area and Tin the area by
flowing a small amount of solder on it. Allow it to cool.
2. Align the desired component on the circuit board based on the placement diagram. While
holding the component in place, apply heat to the tinned pad and re-flow the existing solder until
the component lead “drops” into the solder. Allow to cool and observe the alignment of all of the
leads.
3. If the alignment is acceptable, solder the remaining leads. You need enough solder to cover
the lead and mounting surface of the entire lead length. (See Figure 2 shaded areas) If
necessary, re-solder the original lead.
Input Lead is
angle cut
03
SD
ATF34143
G
S
Figure 1A Figure 1B
Leads flat to trace, 4 places
Some spring back is OK
Typical side view of four leaded surface mounted device, lead bending close to body.
Solder shown in shaded areas
Solder full length of lead, 4 place
PCB Trace
Figure 2
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Soldering surface mounted passive components such as chip resistors and capacitors:
1. Determine the component mounting position based on the assembly diagram.
2. Without the component, tin one of the mounting pads not shared by another component.
(Flow a small amount of solder on it)
3. After cooling, place the component in the correct position per the assembly diagram, it
should now have one end over the tinned area.
4. Holding the component in place with tweezers or other soldering aid, heat the tinned area
and allow the solder to flow around the component. Remove the heat.
5. Once solidified, remove holding tool and heat and flow solder to the other side of the
component only if it is not shared by a second component. If so, solder the component that
shares the pad first. You are done! See examples in figure 3.
Incorrect Component
Placement
Correct
Solder Fillet
Incorrect
Circuit board
Figure 3. Proper SMD Assembly.
Soldering leaded components (resistors, capacitors, diodes, and inductors) :
Depending on your available tools, you can solder your transverter's leaded components
from either the top or bottom of the PCB. It is suggested for the home assembler to use a method
that is comfortable. A simple holding vise can be utilized to allow the components to be 'dropped
in' from the top side and soldered on this side without flipping over the assembly. As an alternate
method, you can insert one component at a time in the correct mounting location and gently push
down to the circuit board, while holding the component, flip over the circuit board and bend the
leads over in opposite direction to hold the component in place. Although this is the most reliable
method, there are some drawbacks if the component must be removed when the PCB is installed
in the enclosure.
Some leaded components may need to be surfaced mounted either on one or more leads.
If this is the case, the leads need to be pre-formed before soldering. If you see a leaded
component on the component placement diagram without a circle at the end of the lead such as
R25 and C49, those leads will need to be surfaced mounted as shown in the drawings below. DO
NOT install any leaded components in the ground via holes if it is shown as a surface mount lead.
The PCB mounts to a pallet and if there is any solder or extended lead interference, the PCB will
not be flush with the pallet.
Leads soldered to PCB surface
This end soldered to PCB surface
Circuit Board Surface
Circuit Board Surface
Figure 4.
Some inductors are pre-formed and some will need to be formed such as L1. It is suggested
that the coils be formed on the supplied wooden dowel. Winding coils is not an exact science and
you should not be intimidated by it. Using the enamel wire supplied, extend about ¼" in a
perpendicular direction off of the dowel and wind the wire around it, counting each revolution as
one turn. When the total number of turns is completed (see the component list) cut the wire an
/Kits/1296-144CK.doc 4 Rev. B 9/20/2007
additional ¼" beyond the dowel. Form the two ¼" leads so they are pointing in the direction as
shown in Figure 5.
1/4"
End view of formed coil
Solder Tinned Area
1/4"
Top view of normally formed coil, (4 turns shown)
Solder Tinned Area
Figure 5.
dowel. The coil forming is complete! To ensure a positive solder connection, the ¼" leads should
be solder tinned as follows. With a solder iron, flow a pool of solder on the tip. Place the desired
end of enamel wire in the pool of solder. It may take a few seconds depending on the iron
temperature, but the red enamel will melt and be replaced with a solder tinning. Also tin L5. It is
pre-wound.
Rework of soldered components if needed
The easiest method to rework soldered components is to employ a de-soldering braid that is
specifically designed for this purpose. It can be purchased at most electronics component
distributors. Place the de-soldering braid on the lead that you are removing and apply heat to it.
Without excessive pressure the solder will flow into the braid leaving the lead or component
ready to be removed.
Printed Circuit Assembly Notes
Your kit is provided with easy to read component placement diagram that details every
components placement and the reference designators that correspond to the provided component
list (Bag 1 - Bag 4). Each side of the printed circuit board (PCB) is also shown to eliminate mirror
image assembly errors. The top and bottom side assembly operation should always begin by
aligning the PCB outline with the out line of the component placement diagrams. The top side of
the circuit board is the side with the printed lettering on it. Most of the soldering will be done on the
topside. Again, when soldering on the ground plane, be sure that solder does not flow and pool on
the bottom side of the PCB.
This is a basic assembly instruction document. Every filter has been installed and tested in
the circuit board. Adjustment should not be required. As of now, this kit is for a average to
experienced RF circuit builder. To align this kit, it will only require a volt meter, a 23 CM signal,
and a power meter that will measure up to 5 watts maximum. If you have access a frequency
counter, a signal generator, and a mW power meter it would be a plus. Please note that this
document assumes the Complete Kit. If you have purchased the 1296-144K, only use construction
details that pertain to the circuit board.
Inventory the parts list. Every part in this kit is important and should be identified. Bag 1
contains resistors, Bag 2 contains capacitors, Bag 3 contains the inductors and Bag 4 contains the
semiconductors and relays. The filters are listed on the components list but are installed. Take
your time to get familiar with the kit contents and verify it is complete. There are extra chip
components packed in the vials, so no need to count them. Just verify that the value is included.
Dress the turns together if they are out of shape from winding, remove the coil from the
Start the Assembly
/Kits/1296-144CK.doc 5 Rev. B 9/20/2007
X
The hardware should be sorted and identified. There are some extras. But remember, No
substitutions or you are on your own!! Review the schematic and the component placement
diagram. Read through all of the assembly steps 1 - 13. Identify every component used. This will
ensure that you have the correct tools and supplies required to complete the transverter. It is also
time to make the last minute decision on building the kit or not. A full exchange towards an
assembled version will be provided if you do not go past this step. We want you to be on the band
and operating not struggling to assemble this because you were not aware of the effort and
techniques required takes to assemble this transverter!
At this time you may want to mark the component placement diagram with the associated
component values by the designators. Simply transpose the component list values to the
component placement document. We do not do this because the values will change over time
depending on availability, engineering changes, or obsolesces. The component list is easier to
update and maintain providing all users the latest improvements or changes to the design.
Updates to the design will be maintained on the DEMI web site in the future. Now! Start the
assembly!
1. Install all bottom side components of the PCB. K1-K3, Q1, and Q2. Do not solder the
cans of Q1 and Q2. All 5 filters are already installed and adjusted!
2. Install all active surface mount active components, Q3, IC1- IC3, IC5- IC7, and IC10 on
the topside of the circuit board per the topside component placement diagram. Do not install IC4,
VR1-VR4, or D1-D9
3. Install all surface mount capacitors and resistors and L31 per the topside component
placement diagram. Review the assembly tips if necessary pertaining to multiple components
sharing the same pad. Be sure of the placement of C57and C59. They are dependent of the
configuration of the transverter you require. Common antenna port (C57 and C59) or split transmit
and receive (C57A and C59A).
4. Wind inductors L1, L3, L9 and L10 as specified in the Bag 3 parts list. Then install all
inductors L1-L31. L5 or L5A placement is dependent on the placement of C59. The molded
chokes L2, and L30 should be surface mounted. L12 is optional and should be installed if you wish
to activate the PTT circuit through your Transceiver’s IF cable.
5. Now install all left over leaded components, pots, resistors, capacitors, diodes, Q4 and
regulators. Do not
install IC4, IC9, Y1, SW1, PTC1, R22, C72, or the LED’s. Do a surface mount
installation of C49, VR3, VR4, R25, R24, R10, R18, D2, D3, D8, and D9. When soldering the
leaded surface mount components, do not allow solder to leak through the ground plane of the
PCB. It will pool up and interfere with the pallet assembly. If you have a question, place the PCB
on the pallet to check.
6. Install the crystal as shown in Figure 6. Do not install the PTC1. It will occur later in the
assembly instruction after testing. The topside component placement shows the crystal standing
up but lay it down over L2 as shown in this pictorial. Again, do not install the PTC.
9Volt Supply
Solder Wire to
Ground and Xtal
~1/8” Space between
PC Board and Xtal
CRYSTAL
tal leads
Figure 6. Crystal and PTC-60 installation detail.
/Kits/1296-144CK.doc 6 Rev. B 9/20/2007
7. Attach the PCB to the pallet. Use two 4-40 x 3/16” screws by the antenna connector and
two 4-40 x 1/4 screws with #4 flat washers by the oscillator section. If you find solder interference
between the PCB and the pallet, remove it by wicking or filing!
8. Attach the connector panel to the pallet. Review the configurations below. Your panel
has all of the holes in it. You may install all of the connectors or just the connectors you desire.
Trim the Teflon on the connectors flush with the panel. Use the 3-48 screws for the SMA
connectors or 4-40 screws for the N connector. The longer 3/8” screws go through the connector
and panel, then into the pallet. The short 3/16” screws hold the connectors to the panel. You may
use the screws to plug the holes if you do not use the connector. After the connectors are
installed, verify that the panel is a flush mount with the pallet and then solder the pins. If you need
to re-position the PCB for the panel to be flush, do so.
9. Use the bottom side component placement as a guide and wire the connections with the
supplied #24 Teflon wire. Install them all as shown. The connection from the +13 VDC connection
and the RCA connector is done with the heavier green wire. Make the connection from the PTT
connector to the PCB. Install the ground lugs as shown with the short 1/8” 4-40 screws and solder
the 1000 ρF caps in place.
10. Find the bottom half of the enclosure (the one with the holes in it) and line up the pallet
with the mounting holes. Insert any two 4-40 x 7/16” screws and start them. Install 2 flat head
screws in the rear panel. Be sure the wires are clear of the ribs and filters and tighten all screws.
If the pallet wobbles, something is being pinched!! Insert the switch into its position but do not
solder. Install the switch panel with 2 flat head screws then solder the exposed leads of the switch.
Install the LED’s. The short lead is ground. Now remove the pallet from the enclosure and trim all
excess leads from the bottom side of the PCB and solder the mounting leads of the switch.
11. Attach the M67715 to the pallet. Use the thermal compound supplied, line up the pins
with the PCB and use the 4-40 x 1/4 “ screws. Solder the 5 pins. Now make a determination of
what keying scheme you will use, PTT-H (+ voltage) or PTT-L (Ground to transmit) and make the
appropriate jumper connection from the PTT connection on the top side of the PCB.
12. Using the matrix below, make a determination of the required IF drive level and decide
if you want a common or split IF. All IF drive levels may be achieved from 1 mW to 10 watts by
following the supplied schematic, matrix, and simplified component layout. The 50 ohm load
(R36) is mounted on the front panel and is installed after the pallet is aligned with the front panel
during final test.
13. Install the IF coax between the IF connector (s) on the rear panel and their proper
locations on the PCB. Refer to the custom pictorial for the correct configurations.
/Kits/1296-144CK.doc 7 Rev. B 9/20/2007
144 MHz. IF Configurations
1-250 mW Drive 200 mW-2W Drive 1-10W Drive
C72
Not Installed
R36 Not Installed
R22
220Ω, 1/4W 220Ω, 1/4W
Not Installed
1ρF
50Ω, 30W 50Ω, 30W
Not Installed
IF Connections, Common or Split
Start the Testing Procedure
1. All of the initial testing of the transverter is done with the pallet assembly only. Before you
start verify that all components are installed except for the mixer, IC4 and the 50 ohm load.
Connect a 13.8VDC supply capable of 3 amps to the +13.8VDC connector. Flip the switch to the
on position (Up) and verify that the LED lights.
2. Test the receive voltages of the transverter first. Use the RX matrix below.
/Kits/1296-144CK.doc 8 Rev. B 9/20/2007
LOCATION RX VOLTAGE Matrix referenced to Ground
Junction of C47 and C48 +13.8 VDC
Output of VR1 (+9)
Output of VR4 (C66)
Junction of IC1 and C7 Between 1.5 and 2.5. Depends if Oscillator is running or not
Junction of IC1 and C9 Between 3.5 and 2.5. Depends if Oscillator is running or not
Junction of IC2 and C12
Junction of IC2 and C13
Junction of IC3 and C13
Junction of IC3 and C16
Junction of IC5 and C29
Junction of IC5 and C31
Junction of IC10 and F5 0 VDC
Junction of IC10 and C70
Junction of Q3 and R30
Junction of Q2 and C6
Junction of Q1 and C3
+9.0 VDC ±0.2V
+5.0 VDC ±0.2V
2.5 VDC ±0.3V
3.5 VDC ±0.5V
2.5 VDC ±0.3V
5.0 VDC ±0.5V
2.8 VDC ± 0.3V
5.0 VDC ± 0.3V
5.0 VDC ± 0.3V
3.8 VDC ± 0.5V
8.5 VDC ±0.5V
9.0 VDC ±0.5V
If any voltages are found to be out of tolerance, check for assembly errors, opens, shorts, or
wiring mistakes on the bottom of the pallet. Some voltages may exceed the tolerances listed. This
is because MMIC’s vary lot to lot. MMIC’s will exhibit a current drain if working. They will either
drop all of the voltage across the resistor if shorted or not draw any current if inoperative. If the
test voltages are close, assume the MMIC is working correctly for now.
3. Be sure to read all of the RF testing procedure. If you have test equipment like a signal
generator, spectrum analyzer, and mw power meter, you may decide not to install the mixer to
complete the testing. The test procedure will cover both methods of testing.
If you do not have the mentioned test equipment, install the mixer, (after verification of the
RX voltages). If you have an mW meter, connect a coax pigtail to the open pad on C17. This will
be the LO circuit’s output and the Mixer’s LO input. This pigtail should have a SMA or BNC type
connector so it can be used for measuring the power level and frequency. Start the oscillators tune
up by spreading the turns of L1 to 1 wire diameter. Probe the junction of R6 and C7 with a
voltmeter. There should be minimum voltage of approximately 0.4 VDC. Adjust C2 to peak the
voltage. You may need to compress L1 if you cannot find a peak. If you have a power meter
connected, verify that the output is +17 dBm (+15 dBm minimum). You may want to slightly
“Tweak” F1 and F2 for maximum power. Do not adjust F1 or F2 after the mixer is installed! After
the voltage is peaked, verify the frequency of operation if you have a frequency counter. If you
installed the mixer, you can probe C17 with a frequency counter. The frequency should be
approximately 1152.000 MHz. You may not be able to adjust C2 to net the frequency. It is not
important at this time and will be adjusted after the final assembly. Just be sure the voltage is
peaked.
4. After the LO has been tested, remove the DC power from the pallet and solder the cans of
Q1 and Q2 to the ground plane. Next find and un-solder one lead from PTC1. Attach the PTC to
the crystal as shown in figure 6. Attach a wire from the crystal case to ground. Keep the lead as
short as possible. The voltage lead is attached to the output pad of VR1, labeled on the component placement as +9. Power up oscillator to verify operation. If OK, attach the shield over the
oscillator with the two 4-40 x 1/4” screws and two #4 flat washers. Be sure not to short the output
/Kits/1296-144CK.doc 9 Rev. B 9/20/2007
of F1 to the case. Position the shield as shown on the component placement diagram. If you are
unsure about the shield shorting the F1 filter, you may cut a small notch in the shield by C12.
5. The RX testing is as follows. Install IC4 now if not previously done. Connect the IF port of
the transverter to a 144 MHz transceiver or spectrum analyzer and adjust R14 counter clockwise.
Inject a 1296 signal into the antenna or RX port (-30 dBm or so) with a signal generator or use a
signal on the 23 CM band. Adjust C59 and C60 for maximum signal strength on the spectrum
analyzer or in the 144 MHz transceiver. Tune for max gain. This will be very close to best noise
figure. When complete, cycle the transverter power on and off to detect the gain in the receiver. A
final adjustment will be made after the final assembly is complete so you do not need to make it
perfect. Just verify that the receiver has gain. If you have a analyzer, this would also be the time to
“Peak” F5 and F3 but it shouldn’t be necessary.
6. Transmit testing is next. Disconnect all cables from the transverter and install the pallet into
the bottom enclosure Start all 6 of the 4-40 x 7/16” screws. Do not tighten. Start the rear panel
screws. Then install the front panel and gradually tighten all of the 10 screws together to ensure a
good fit. Tighten everything evenly to be sure that the pallet is resting on the ribs in the enclosure.
Be sure not to pinch any wires. Connect a 50 ohm load either on the TXRF port or the antenna
connector. Then connect the DC voltage and power it on. To test the TX voltages, key the PTT
line (PTT-H or –L) and measure to verify against the TX voltage matrix. If any voltage is out of
tolerance, verify all surrounding components and recheck bottom side wiring. Remember, MMICs
draw a specified amount of current but may be a bit out of tolerance
LOCATION TX VOLTAGE Matrix referenced to Ground
Output of VR3 (C55)
Junction of IC6 and C38
Junction of IC6 and C39
Junction of IC7 and C39
Junction of IC7 and C42
Junction of R12 and D2
Junction of D3 and L10
Junction of D1 and K3 +13.8 VDC (if K3 is not installed, no need to test)
Junction of D7 and K1 +13.8 VDC (if K1 is not installed, no need to test)
Junction of L30 and C53
+9.0 VDC ± 0.3V
+2.5 VDC ± 0.5V
+4.5 VDC ± 0.5V
+1.5 VDC ± 0.5V
+6.0 VDC ± 1.0V
+1.6 VDC ± 0.3V
+0.7 VDC ± 0.3V
+9.0 VDC ±0.3V
7. To RF test the transmit section, If you need to use your 2 meter transceiver, install the 50
ohm load if it is required for your configuration. Connect a power meter that can measure 5 watts
@ 1296 MHz to the TXRF or ANT connector Connect your IF drive source to the BNC connector
(common IF or TXIF). Check your drive power level before applying drive. Adjust R20 clockwise
for maximum attenuation. Key the PTT line and apply TX drive either from your generator or
transceiver and adjust the R20 to obtain a desired output power. The output power will depend on
the IF drive level setting of R20. If you cannot obtain the correct output power by adjusting R20,
check your configuration and measure your drive level. Do not assume that there is too much
attenuation in the IF section if the unit will not make the output power specification and change the
attenuation values. If the IF is configured for a lower drive level, damage may occur to the mixer if
it is over driven even for a short period of time. If you have variable output power on your 2 meter
transceiver or generator, set it to the minimum and raise it until saturation occurs. This is when the
output power does not increase when the drive level is increased. If this happens, suspect a
/Kits/1296-144CK.doc 10 Rev. B 9/20/2007
problem in the TXRF section of the transverter. If the transverter does not appear saturated,
suspect a problem in the IF section.
Final Assembly
Check all screws and connectors for tightness. Place the top lid on the enclosure
and allow the unit to operate in receive for 1 hour with either a load or an antenna connected. The
unit will become warm to the touch. If you have a 23 cm signal and the IF transceiver connected,
you may notice some frequency drift. After the first hour of operation, the majority of frequency drift
is complete and the oscillator will be stable enough for netting the frequency if required. Remove
the cover and adjust C2 to match the frequency of a know signal or measure the LO frequency at
C17. If the desired frequency cannot be obtained before the oscillator either shuts off or becomes
unstable, determine if it is to high in frequency or to low. If it is to high, remove the LO shield and
compress the L1 inductor and readjust C2. If the frequency is to low, spread the coil slightly and
re-adjust C2. If the frequency is still to low a circuit modification will be required. The circuit
modification is described below but technical details are covered in our Design Note #16 found in
the library section of DEMI web site (www.downeastmicrowave.com). The modification is simple.
After the shield is removed from the base oscillator section, remove the crystal and L2. Do
not remove the PTC form the crystal!! Cut and remove the now empty pad still connected to R5
and R4 between the placement of L2 and the R4, R5 combination. Install a 10 pF chip cap across
the gap in the cut pad. See figure below.
The chip cap becomes a series cap between the L2 /crystal and the R4/R5 connection.
Then re-install L2 and the crystal and retest. You may need to spread or compress the L1 inductor
for best results. Net the frequency, install the shield and allow the unit to warm for 10 minutes
before the final adjustment is made.
/Kits/1296-144CK.doc 11 Rev. B 9/20/2007
When complete you may retest the RX and TX section and re-adjust the IF levels as
desired. If complete, attach the lid and the 4 screws or you may also wish to install some or all of
the user options. They are listed starting on the bottom of this page.
Completion
This completes the assembly and testing of the 1296-144CK. You now have enough
knowledge of how this assembly works that implementing it into a complete working transverter
system should not be a technical problem.
The receive conversion gain is limited for a reason. This receive section will not overload in
a RF dense environment. If the transverter is to be used in a high performance terrestrial or EME
set up, a mast mount LNA that has better noise figure performance will be desired. If so, additional
filtering may be required and the use of the IF amplifier may need to be omitted. Simply adding a
LNA to the front of the transverter will improve the noise figure but will degrade its dynamic range
by the amount of gain added. It is not recommended to add an LNA unless it is mast mounted. If
a higher power amplifier is added, also consider and additional filter and isolator.
DEM 1296 -144 User Options and performance Improvements:
Add an external preamplifier for noise figure improvement.
If a better noise figure is desired, simply placing a LNA with a modest gain at the antenna
will solve that problem. Understand that the addition of gain in front of this stock transverter will
degrade the IMD performance, and reduce the dynamic range of the transverter by more than the
amount of gain added. You may get a way with doing nothing more than adjusting the RXIF gain
control if you operate in a non-hostile RF environment. If your LNA is a ultra low noise unit, it most
likely will not have the IP3 performance the transverter has. It will overload before any component
in the transverter will. So, your receive system now becomes limited by it’s external LNA’s
performance. If you increase the gain performance of your external LNA, (25-30 db) you may
consider bypassing the transverters LNA completely because it’s IP3 performance is totally
controlled by the external LNA. To do so, remove L5, L31, C59, R31, and R30 from the circuit.
Then connect a short piece of coax between the RX antenna and C63. Be sure to keep it as short
as possible and solder the grounds.
Another option is to remove the IF amplifier. If you need to reduce the gain by less than 10
dB, remove IC5 and R18. Then you may use a 100 pF disc capacitor and place it from where the
input and output leads of IC5 was. You may then still adjust the RXIF control to your desire.
Install / Remove RXIF gain stages:
This was briefly discussed in the external preamplifier section. For whatever reason, you
may require additional gain or have too much IF gain. IC5 can be installed or removed at any time.
Be sure of your systems performance when deciding to make a change. You are also not limited
to the supplied ERA 6 MMIC. You may choose a higher gain unit. The ERA 6 was chosen for its
IP3 output performance. Using this MMIC doesn’t degrade the transverters overall performance. A
high gain MMIC will not only reduce the IP3 by the difference in gain but will also degrade the
system if a lower IP3 output device is used. In the future, this MMIC will change as soon as
something better become available.
If changing or removing the MMIC, be sure to add or remove the correct choke and bias
resistor for the desired MMIC. The RXON signal is the same voltage that the transverter operates
on so calculate the new bias resistor based on that voltage.
/Kits/1296-144CK.doc 12 Rev. B 9/20/2007
Additional RX selectivity:
If you find yourself requiring more selectivity from lower frequency out of band products, a
modification can be performed. The alignment is very critical and virtually cannot be done without
test equipment. A minimum of a steady level, signal source is required. In the factory, we would
not ever think about doing this with out a noise figure meter. The mod goes like this. In bag 3 of
your kit you will find a 2 turn red coil and a piece of buss wire. The coil is designated L6A. First,
remove L6 from the circuit. It is a single turn and blue. Install L6A and the same side as L6 but as
close to the gate lead of Q3 as possible. Do not stretch the coil! Solder the other end on the
ground. Then cut 0.400” of buss wire. This wire will form a shunt inductor. Put a slight bend in the
wire and attach it on the same side as L6A but as close to the FET side of C59 as possible. Tack
solder the other end to ground. Then push the wire close to the boars as possible without
touching. Now measure 0.250” from C59 and put a solder bead on the wire to ground. You may
now re-tune the front end for maximum gain. You may do an on the air test to check for additional
selectivity. It should perform better and if not there is little hope with out and external bandpass
filter! What is the noise figure? We have seen the best at 1.5 dB and the worst at 3.5 dB by tuning
for maximum gain. In the factory we assemble all of the transverters with this mod. They are all
tested on a noise figure meter and we find at some time we need to sacrifice some gain to improve
the noise figure. Good luck with this mod!
Auxiliary Switching contacts:
The auxiliary contacts in K2 are labeled C (common) NO (normally open) and NC (normally
closed). The C connection can be wired to ground or positive voltage such as the source +13.8
VDC. The K2 common connection will then be toggled depending on what state the transverter is
in. The contacts are marked for the receive mode. The NO or NC can be wired to the AUX
connector on the enclosure.
Peak Performance.
So you want the best possible performance possible? Unless you have a signal generator,
noise figure meter, spectrum analyzer, and a microwave power meter, you have given it your best
shot. If you do have this equipment, then have at it. Every filter can be optimized to your
operating frequency for maximum selectivity and minimum insertion loss. All of the filters have
been tuned into a 50 Ohm system. Once they are connected to the active components, they now
have some mismatches. Please understand that these mismatches are not crucial to the operation
of the transverter, but they can be minimized. Do what your engineering skills allow you to do. You
could always find a dB or two and reduce the amount of spurious emissions. You may also find
out that if you reduce your TX drive level, the spurious improve. A lesson well learned in mixer
saturation. Have fun!!
Frequency Stability
If the frequency stability is the problem, remove the shield and re-peak the voltage. When
adjusting for frequency, the oscillator is sometimes left on the edge of operating. When on this
edge, the frequency will be unstable. After the voltage is peaked, replace the cover on the LO and
allow it to warm. Check for stability. If stable, follow the frequency netting instruction (DN016)
found in the final assembly section of this document. If the voltage is peaked and you still
experience drifting (greater than 300 Hz. After a 10 minute warm up), record its tendencies and
consult DEMI with the problem. Stability is the function of temperature and component tolerance.
If you are sure the LO section is assembled correctly we can help.
/Kits/1296-144CK.doc 13 Rev. B 9/20/2007
Conclusion
We hope you had fun with this kit and that you enjoy many hours of operation with this
transverter. The goal of this kit was to economically provide the radio amateur with the highest
performance available in a 23 cm transverter while maintaining a compact and portable design.
We wish you years of fun and excitement working many contacts both local and DX!
Good luck on the band!
DEM 1296 -144K and CK Component List
BAG 1 CONTENT
Resistor (R) values are in Ohms and are chips unless otherwise specified.
R1 470 R9 130 R20 1K POT R28 24
R2 1K R10 56 1/2W leaded R21 220 1/4W leaded R29 24
R3 1.5K R12 1K 1/4 leaded R22 220 1/4W leaded R30 12
R4 100 R13 220 1/4W leaded R23 1K R31 330
R5 51 R14 1K POT R24 330 1/4W leaded R32 12
R6 100 R15 220 1/4W leaded R25 180 1/2W leaded R33 1K
R7 100 R18 150 1/2W leaded R26 1K 1/4W leaded R34 5.1K 1/4W leaded
R8 130 R19 220 1/4W leaded R27 470 1/4W leaded R35 5.1K 1/4W leaded
BAG 2 CONTENTS:
Capacitors (C) values are in ρF and are chips unless otherwise specified.
C1 0.01µF
C2 1 - 4 Piston C21 18
C3 0.01µF
C4 18 C24 100 C42 33 C63 33
C5 22
C6 0.01µF
C7 0.01µF
C8 0.1µF
C9 33 C29 100
C10 1.0 µF Tant. C30 0.1µF
C11 0.1µF
C12 33 C32 100
C13 33
C14 0.1µF
C15 0.1µF
C16 33 C36 100 C57, A 33
C17 33
C18 33 C38 33 C59, A 0.3-3 VAR.
C20 100 C39 33 C60 0.3-3 VAR.
C40 0.1µF C61 0.1µF 1008
C23 18 C41 33
C25 0.01µF C43 0.1µF
C26 100
C27 18 C48 100
C28 18
C31 100 C52 100 C70 33
C33 0.1µF OPT. C54 0.1µF C72 1 ρF leaded
C34 100
C35 100
C37 0.01µF C58 100µF Elect.
C47 0.1µF C65 0.01 µF
C49 2.2 µF Elect.
C50 0.1µF C68 0.1µF
C51 100
C53 1.0 µF Tant. C71 0.01 µF
C55 1.0 µF Tant. C73 0.1µF
C56 0.1µF
C62 0.1µF 1008
C64 33
C66 1.0 µF Tant.
C67 33
C69 0.01 µF
10 pF optional (1)
BAG 3 CONTENTS:
All inductors have the enamel wire size and turns specified. Identify the
Molded chokes by body color and band colors. All others are as indicated.
L1 3 Turns 1/8" ID #24 Wire (HW) L9 5 Turns, 1/8” ID #24 WIRE (HW)
L2 0.10 µH (Small body, brown-black)
L3 6 Turns 1/8" ID #24 Wire (HW) L12 1.0µH (brown/black)
L5, A 5 Turns 0.05”ID #28 Wire (pre wound)
L6 1T, BLUE Body (pre wound)
L6A 2T, RED Body (pre wound) optional 1” # 18 buss wire
L8 5 Turns #28 Wire (pre-wound) 1 - wooden dowel
L10 5 Turns 1/8" ID #24 Wire (HW)
L30 0.33 µH(Green body, orange bands)
L31 10 ηH (0603 chip inductor)
/Kits/1296-144CK.doc 14 Rev. B 9/20/2007
BAG 4 CONTENTS:
Note that all filters (F1-F5) are pre-installed in your PCB.
Q1 2N5179 D9 1N914 IC6 MAR3
Q2 2N5179 F1 112570C - Installed IC7 MAV11
Q3 ATF34143 F2 112570C - Installed IC10 AH31
Q4 KN2222 F3 123080C- Installed VR1 78S09
D1 1N4000 type F4 123080C - Installed VR3 78S09
D2 MPN3404 F5 123080C- Installed VR4 78M05
D3 MPN3404 IC1 ERA3 K1 G6Y-1
D4 HSMP 3814 IC2 ERA2 K2 G5V-2
D5 1N4000 type IC3 ERA5 K3 G6Y-1
D6 1N914 IC4 SYM-14H PTC1 PTC 60 Thermistor
D7 1N4000 type IC5 ERA 50 Y1 Crystal 192.000 MHz HC 18/U
D8 1N914
HARDWARE
(2) 1000ρF leaded R36 THC 50 Ω, 10 W Load
(1) Type ¾” "N" connector SW1 Power Switch
(2) SMA connectors (1) Shield- Prepped
(2) BNC Female UG1094/U Connectors (3”) #18 Teflon wire
(3) RCA Jacks (Control, Aux., Power) (3’) #24 Teflon wire
(4) 4-40 x 3/16” Screws (20”) Coax
(2) 4-40 x 3/8" Screws (1) 3/8” Hole Plug
(4) 3-48 x 3/16” Screws (4) Adhesive Backed Rubber Feet
(4) 3-48 x 3/8” Screws (1) Set of Labels
(5) 4-40 x 1/4” Screws (1) 1/4” Plate
(6) 4-40 x 7/16” Screws (1) Switch Panel
(2) 4-40 Nuts (1) Connector Panel
(2) #4 flat washers (8) Flat Head
(2) #4 lugs (1) Machined Enclosure
(2) LED, RED (1) Thermal Compound
(2) 4-40 x 1/8” Screws
Miscellaneous Loose Parts if required in you kit (1) RF Power Module IC9, M67715. (2)
Printed Circuit Board with filters
installed. (3) Enclosure, two halves.
/Kits/1296-144CK.doc 15 Rev. B 9/20/2007
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