DEMI Part Number L144-28_____ SN___________
Power Out Maximum:
25 W linear 50 W linear Other_______________
Noise Figure and Gain:
<1.0 dB maximum @ 17 dB conversion gain minimum
DC Power Requirement:
11.5 - 15.5 VDC @ 6 Amp Max. 12 Amp Max.
RF Option:
Common Separate TX and RX (Split)
IF Option:
Common Separate TX and RX (Split)
IF Drive Level Maximum:
Keying Option:
PTT-L ( to ground) PTT – H ( Positive Voltage)
Options:
IF Drive Sense
Negative Voltage Generator
Aux Connector Pin #
Transmit
Receive
1 (Sequencer step 1)
High Low Open
High Low Open
2 (Sequencer step 2)
High Low Open
High Low Open
3 (Sequencer step 3)
High Low Open
High Low Open
4
5
6,7,8
Ground
Ground
Oscillator Option:
Standard
Dual
Synthesizer Only
Transverter Configur a t ion
Transverter Sequencer Transverter Sequencer
Customer Specified Options: None See Below
__________________________
__________________________
__________________________
__________________________
/Built/L144-28rB.doc 1 Rev. B 4/2/2012
Configuration Overview: The DEMI VHF/UHF transverter line is designed to interface and
operate with most High Frequency transceivers that are available on the market today. Since you
choose to purchase an assembled unit, it has been configured by DEMI, per your specifications, to
interface with your desired transceiver. This configuration may be changed or altered at any time if
you desire to utilize a different transceiver or change you system configuration. Let’s review your
configuration and verify that your interface will be trouble free. Please refer to the front page.
DEMI Part Number Verification: All DEMI VHF/UHF transverters contain the operating
frequency within the part number, i.e., L144-28HP is equated to 144 MHz is converted to 28 MHz.
If you ordered a special frequency conversion, it will be listed here. Also, please understand that
the conversion is simple math. If you desire to operate on 145.500 MHz. with your L144-28, it will
require you to adjust you transceiver to 29.500 MHz.
Power Out Maximum: The part number will indentify the transverter as either a high power (HP)
or a standard power unit. The output power will be circled or marked other with a hand written
level on the line. This level, 25W, 50W or other, is the linear output power level that should not be
exceeded if linear operation is expected. The transverter may be capable of producing higher
output power but is not recommended because of excessive heating that will interfere with its
frequency stability while producing excessive “on the air” distortion products
Noise Figure and Gain: The noise figure and gain listed are nominal minimum requirements
and most transverters exceed these specifications. In utilizing the latest PHEMPT technology, we
have designed the complete receive section of the transverter with extra filtering, di-plexing, and
gain management in mind. Th ere is also a RXIF gain control that is adjusted by the user to set the
“S” meter level on the transceiver. External receive pre-amplification interfacing will be covered
later in this document.
DC Power Requirement: The DC power requirement is listed and should be used as a guideline.
The standard and High Power transverters do require different supply currents. Please include
some “Buffer” in your power supply to eliminate voltage drop delivered to the transverter. Basically,
do not utilize a 5-amp power supply for a 5-amp requirement transverter.
RF Option: The RF option is either a single port (Common RF) for both TX and RX or there will
be two separate ports, (Split RF) one RX and one TX. With the standard level unit, there will be a
PC board relay doing the Common RF switching. The HP unit will have a coaxial relay mounted to
the connector panel of the transverter and will be an additional cost option. The standard level unit
may be changed from Common to Split if the user desires. It will be covered in the manual. The HP
transverter will require additional components to change. The TR relays are controlled by the
Push-to-talk (PTT) circuit.
IF Option: The IF options are much like the RF option but in reverse. The transverter may be set
up as Split IF (separate TXIF and RXIF in/out lines) or can be configured as a Common IF. There
is on board relay that will switch the RX and TX to the correct direction and is controlled by the PTT
circuit.
IF Drive Level Maximum: Depending on your transceiver or your specific IF drive requirements,
the transverter will operate at its maximum linear output power with your specified maximum drive
level. There is a TXIF gain control with 15-20 dB of range to allow the user to set a specific output
power less than maximum. The overall drive level range is determined by different sets of
/Built/L144-28rB.doc 2 Rev. B 4/2/2012
attenuators and gain stage levels if required. The useful operating “Range” will be between your
specified maximum and approximately 20dB less.
Keying Option: The keying options are either PTT-L or PTT-H. PTT-L requires a connection
to Ground to transmit. This is the most common keying option. PTT-H requires a voltage between
1.7 and 17VDC to transmit. This option can also be placed on the IF coax if desired. If you desired
the sequencer to be utilized, the PTT connection will go directly to the sequencer to key it. It in turn
will key the transverter on the last step of the sequence. Now doing so creates other problems if
you choose to use a High IF drive level (above 200 mW). This is covered in the Options: section
of this document.
Options: The IF Drive Sense option will be installed with any IF drive level above 200 mW.
This circuit is a protection circuit that will prevent excessive IF drive levels from damaging the RXIF
circuitry and the Mixer. When utilizing a high- level IF drive transceiver, the IF drive is applied at
the same time as the PTT is energized (unless your transceiver has some sort of delay circuit built
in). If the transverters sequencer is utilized, the transverter will be keyed last in the sequence. This
will result in the high level IF drive being applied to the transverter’s RXIF section which could
cause damage to the circuit and Mixer. The IF drive sense circuit detects high- level drive and
enables the TXIF attenuator. This is done to protect the transverter’s RXIF section and Mixer. It
then holds and waits for the Transverter to “Catch up” in the sequence. This circuit will allow a user
to key the sequencer circuit with the standard PTT circuit of a transceiver without having an issue
or requiring external wiring or modifications to the PTT circuit.
This circuit will also protect the transverter in case the PTT circuit fails between the
transverter and the transceiver. If the transverter is keyed directly with the PTT (sequencer is
disabled) it will function normally.
The IF drive sense circuit should not be used to key the sequencer because it will produce
long delays between transmit and receive or chop off the beginning of a transmission. If the
transverter is configured with the IF drive sense enabled for any other purpose than protection, it
will be discussed with you before delivery to assure its proper operation.
The Negative Voltage option is utilized by transceivers without transverter ports and ALC
inputs to adjust the output power of the transceiver. If the transceiver has an ALC input, this
connection can be made through the AUX connecter and will be indicated.
Aux Connector Pin #: The AUX connector is just that. All other I/O’s of the transverter are
found in this connector. All transverters will have the sequencer pre-wired and will be indicated
how it is configured. There are extra pins in the connector and may be specified by the user for
various IN/OUT configurations. They will be indicated as such.
Oscillator Option: The standard Oscillator is crystal unit. If the Dual oscillator is requested, it will
include a Synthesizer that is switchable using the center off power switch. Up is the standard
oscillator and down is the synthesizer with indicated operation with the “LOC” led. The third option
is the synthesizer only of the local oscillator. The synthesizer requires a 10 MHz reference.
Customer Specified Options: All other customer specified options will be listed and identified.
If for the reason of installing, other options were eliminated, it will be specified and detailed with
any special instructions required for correct operation.
/Built/L144-28rB.doc 3 Rev. B 4/2/2012
DC POWER
TX
AUX
PTT
10 MHZ
TX IF
IF
ANT/RX
Installation
Theory of Operation: The basic principle of a VHF/UHF transverter is to convert a chosen
band of operation to the 28 MHz. band of a HF transceiver. Following the recommendations of the
HF transceiver’s operation manual for transverter use is the most important aspect of correct
transverter operation. If configured correctly, the transverter will convert both transmit and receive
signals to a new band of operation and seam “invisible” to your HF transceivers operation. In
simple terms, the transverter will not improve the performance of your HF transceiver but will not
cause any degradation of performance in any way.
Interfacing and Operation: The interfacing starts with a complete understanding of your HF
transceiver and manual. The manual should cover the setup for transverter operation and the
connections to be made to the HF transceiver. Some transceivers are simple and some are
complex. Some transceivers may have more than one correct way of interfacing. Hopefully, you
have decided on how this transverter is to be interfaced at the time of order so we were able to
configure the transverter to fit your requirements. If you find that this transverter is not configured
correctly, refer to the Option Setup section of this manual concerning changing of configuration or
contact us directly. All configurations are user changeable and detailed instructions are included.
Start the interfacing with good quality 50 ohm cables for the IF (28 MHz.) and 10 MHz.
connections. These connections are low level (25 watts or less) and are BNC connec tor s on t he
transverter. Your HF transceiver may have various other types of connections. We find that simple
RG-58 type BNC cables work fine with or without adapters to your HF transceiver. All transverters
will require a PTT (to ground or positive voltage on TX) to enable the transmit mode of the
transverter. The PTT input to the transverter is a RCA connector. This cable does not need to be
shielded, but extra protection in a QRO station is a good idea! Most transverters have RCA
connectors for PTT outputs but others have various connections. Be sure to have whatever cable
that is required ready to go. The DC power cable is supplied with the transverter and needs to be
prepped on the power supply end. The AUX connector will contain all sequencer connections and
any other special customer requirements. The matching connector to the AUX connecter is
supplied and should be wired before interfacing unless further testing of your system is required.
Review the pictorial of the rear panel and/or the rear panel of the transverter.
Connect your transceiver to the transverter: Interfacing the transverter to the transceiver
is easy. After reviewing the front-page configuration and verifying that it is configured correctly for
your purpose, begin cabling. An Important note: It is recommended that during the initial setup of
the transverter, that it is not connected to your complete system with a HPA or mast mount LNA.
All aspects of the transverter’s performance should be tested before a complete installation is
/Built/L144-28rB.doc 4 Rev. B 4/2/2012
Rear Panel view
made. Drive levels need to be established and proper switching needs to be verified before
complete integration.
1. Connect the DC POWER to the transverter. It is supplied with the matching cable. 13.8 volts is
optimum but the transverter will operate normally from 11 to 15 volts. Verify the DC power
consumption of the transverter and use a power supply with some headroom. Cycle the power
switch on the transverter and verify the Green light. Leave the transverter powered off.
2. If one of the synthesizer options was indicated, connect a 10 MHz reference to the 10 MHz
connector and cycle the power switch. If you have the “Dual: option the switch will be a center
off and the synthesizer is active with the switch in the down position. Remove the 10 MHz
source connection to verify loss of loc while the transverter is powered up. It should produce a
blinking or no LOC light at all. Reconnect and cycle power to verify LOC performance.
3. If you ordered the Negative voltage option to use with your transceiver’s ALC circuit, refer to
the Option Setup section in this manual for details on set up and test your transceiver for
transverter operation.
4. Connect the IF cable/cables. The transverter may have a common IF port or two separate
ports, TXIF and RXIF for the IF connections. The connector labeled “IF” is either the common
port or the RXIF port depending on your requested configuration. Verify on the front sheet. The
IF cable is either connected to a transverter port connector or the main Antenna connection of
you transceiver. Refer to your manual.
5. Connect the “Push-to-Talk” line out of your transceiver to the transverter. It is a RCA connector
labeled PTT on the transverter. Refer to the configuration sheet for the type of keying required.
6. If separate TX and RX ports were ordered, the internal transfer relay option has not been
assembled. The separate ports are labeled TX and ANT/RX. If you have requested a common
RF connection, the “ANT/RX” port has both TX and RX functions. Connect your antenna
system or dummy load with a power meter to the appropriate RF connector on the transverter.
7. On the bottom of the transverter, verify the TXIF and RXIF gain controls in the transverter. Turn
the RXIF control fully clockwise and the TXIF control counter-clockwise. This is maximum
attenuation on Transmit and minimum attenuation on Receive.
8. Power your transceiver “ON”. If you transceiver cycles during power up, it may key the
transverter. This is indicated by the Red “XMIT” light and the sound of relays cycling. Verify that
the HF transceiver is in” receive” and that the red XMIT light is off on the transverter. If not, shut
off your HF transceiver and check the PTT connection with the IF cables disconnected from the
transverter. If both transceiver and transverter are in their receive modes, tune the transceiver to
a frequency between 28.100 and 28.250 Mhz. unless you ordered a “none standard frequency”
transverter and then depending on the conversion frequency, select an IF frequency in the
middle of you operation range.
9. Observe the noise level in the transceiver on the “S” meter and by ear. If it is too high, adjust
the RXIF gain control in the transverter counter-clockwise until a slight noise increase is heard in
the transceiver or just a slight movement in the “S” meter is detected. Power the transverter on
and off to verify the change. The RXIF gain may be increased beyond this point, but it will start
to degrade the dynamic range of your transceiver. It is all user preference. If you plan to use an
external or mast mount LNA, this level will need to be re-adjusted. Find a signal on the band or
use a signal generator to determine correct frequency, or minimum signal level.
10. It is now recommended to test the transverter’s transmit section in the CW mode because most
transceivers have carrier level or power level controls in this mode only. If your transceiver
requires the use of the “negative voltage option” you may not have a power adjustment ability
on your transceiver. Do not use full or semi break -in if possible. Do not use FM, SSB or AM
because it may not be possible to obtain maximum output power with a transceiver in these
/Built/L144-28rB.doc 5 Rev. B 4/2/2012
modes. Set the carrier/output power control to minimum or “0” output power (if you can). Place
the transceiver into transmit. If the PTT circuit is connected correctly, the red “XMIT” light on the
transverter will switch on. While observing the built in relative power meter or an inline RF
power meter, slowly increase the carrier control (with key down) or increase the power output
control to the maximum desirable IF drive level obtainable by your transceiver (maximum of 25
watts!) If this level is not what is indicated on the front page of this document, do not exceed
that level. If you find that the transverter is not set-up for your transceiver’s range, go to the
Option Setup section and re-configure the transverter before further testing.
If the transverter is configured correctly for your transceiver, minimal power may be detected
on the power meter. With the transceiver’s drive level at maximum specified for the transverter,
slowly adjust the TXIF control in the transverter in a clockwise direction while observing the
power meter. Set it to any desired level between 0 and the maximum specified output power.
The relative power meter is set to show 9 bars lit for the specified maximum linear output power.
This may vary with a bad VSWR but will be true into a 50 ohm dummy load. Switch the
transceiver to USB and make a transmission. The power output and current drain should
correlate to your speech pattern.
11. You may re-adjust both RXIF and TXIF again if desired. The receive amplifier section and local
oscillator frequency should not need to be adjusted but you may if you wish. Do not adjust any
of the helical filters unless you have access to a spectrum analyzer at the minimum.
12. The AUX connector mate may be now wired for your installation. If you require something other
than what is indicated on the front page, please see the Option Setup
section for further details .
Also read further about interface and testing a mast mounted LNA in that section.
Basically, the transverter is ready to use and may be integrated into your system. Connect as
you wish to use it in your system. If your system requires the use of the sequencer or you desire to
implement it please refer to the Option Setup
section of this manual.
General Operation: General operation of the transverter, if everything is adjusted correctly,
should be transparent to the transceiver and the user. Except for the frequency read out, (if your
transceiver doesn’t allow its display to be adjusted for transverter operation) it will be like operating
on 10 Meters. All of the functions of the transceiver (filtering, DSP, split band operation, dual VFO)
will be transposed to the frequency band of the transverter.
Some cautions should be taken when operating CW or VOX. Operating the transverter in a
“Full Break-in” mode is not recommended. Because of the mechanical relays in the transverter,
there will be too much delay to operate “Full Break-in” effectively. AND—the relays would be
abused if “Full break-in “is enabled. It is best to operate in “semi break-in” and adjust the delay of
the PTT on your transceiver to match your comfortable CW operating speed in a way that the delay
will hold the PTT until your transmission is complete. Since all transverters will be delivered with
the sequencer enabled, this delay will need to be longer to allow all components within the system
(Power amplifier, LNA, relays,) to complete their transition if utilized. It the stock transceiver is to be
used alone, the transceiver PTT signal may be connected directly to the transverter’s PTT input if
the sequencer is bypassed. This will shorten up the delay but will not allow “full break-in” without
relay chatter. See the Sequencer Operation in the Option Setup section of this document.
Unless the Synthesizer option is in use, the transverter will experience frequency drift
through aging. The frequency of the transverter’s local oscillator has been “Netted” on our test
bench at its normal operating temperature after a 24 hr burn-in. This will minimize its frequency
shift from ageing but may need to be re-adjusted after prolonged operation. This is because of the
/Built/L144-28rB.doc 6 Rev. B 4/2/2012
physical nature of crystal ageing. As the hours of operation time increase, this “Zero Offset”
frequency will be less and less and will not require adjustment to “Net” the frequency.
As for frequency drift during operation, great care has been taken to minimize it. The
oscillator section of the transverter board is “Ovenized” and the speed of the cooling fan on the
heat sink is controlled by the actual heat sink temperature. The problem still arises from the
internal air temperature of the transverter and the heat conduction of the heat sink to the oscillator
section of the transverter board. Frequency drift is slight for SSB and CW operation but carful
understanding of the drift is important for digital mode operation. Our testing was done with 30
second transmit and receive times at the transverter’s full rated output power. This has shown that
the most extreme drift will occur during the first few transmissions while the transverter reaches its
stable operating temperature. If the room temperature is less than 75 degrees F (approximately 25
degrees C) the fan may not be running. The first transmission will cause the Fan to cycle and if the
heat sink temp rises, it will remain running slow. This first cycle will cause the largest frequency
shift of about 10 Hz. The next 3-4 transmissions will stabilize the frequency drift after moving no
more than 25 Hz. After a total of 5 transmissions, the frequency drift will be 1 Hz or less if all
conditions remain the same during 30-second cycles of transmit and receive. Of course this may
better or worse depending on the transmit power and duty cycle. An operation recommendation
would be to start your digital schedule a few minutes early and you will achieve frequency stability
at the actual start time of the schedule.
Removal of the fan from the 25-watt transverter will allow the transverter to drift as much as 150
Hz over a ½ hr. schedule. This may be acceptable for SSB and CW operation but we have found
the ambient fan noise of the transverter to be un-noticeable. The removal of the fan on the 50-watt
transverters will allow the transverter to overheat and damage the output power module. Because
of the heat sink structure of the High power transverter, the ambient noise of the cooling fan is
greater but still not annoying in our opinion.
Option Setup:
Common or Split IF Option: The IF configuration may be change at any time according to the
type of transceiver you are utilizing. Refer to the Component placement or schematic for
clarification. The component designators are also screened on the circuit board.
K3 is the common IF relay. To split the IF lines into separate RXIF and TXIF, remove the IF
coax from its position on the board (junction of C93 and C94) and re-attach the center conductor
between C95 and K3. You may need to scrape a little solder resist from the pad before soldering.
The shield may be now soldered where it was on the ground pad marked COM. The TXIF cable
can be prepped and soldered to the pad between K3 and C92. Again scrape the solder resist if
required. The shield can be soldered to the ground pad labeled TXIF. Install a BNC connector in
the rear panel (TXIF) and attach the TXIF coax. Reverse the procedure if you want to change to or
back to Common IF.
Please not that if you have a separate IF configuration, the IF drive sense option will no
longer function. It is not necessary with the split IF. It is to protect the RX circuit and Mixer.
TXIF Drive Level Range: The TXIF drive level range can be changed at anytime to conform to
your transceiver type. Basically, there are three configurations. For high IF drive levels, (250 mW25 watts) the 50 Ohm load will be installed with a low value capacitor in the C91 position (10 pF or
less for 25 watts). Mid level drives between 1mW and 250 mW will not have the load installed and
will have a 1000 pF capacitor installed for C91. For the low drive levels (-20dBm to 0dBm or 1mW)
IC7 will be installed. If you desire to change the drive level for whatever reason, just duplicate the
info above. To install IC7, cut the ribs in the trace before installing. -10 to -6dBm inputs, use a
/Built/L144-28rB.doc 7 Rev. B 4/2/2012
MAR-3 for IC7. For -20dBm, use a MAR-6. Other MMIC’s may be used but the bias resistor R33
may need to be changed. Adjust R36 to obtain desired level in all cases.
IMPORTANT NOTE: Do not assume that since your output power of the transverter is low
that it is because you do not have enough IF drive. Please consult DEMI if you have problems
obtaining full output power with your specified drive level.
Common or Split RF connections: The common RF connection will be different depending on
the output power model you have. If it is a High Power unit, the common relay will be installed on
the rear panel of the transverter. Follow the cables from the relay to the circuit board. The relay
may be removed and two separate type “N” or UHF connectors may be installed in the rear panel
with coax to the C62 pad for RX and the C57 pad for TX. The relay may be left installed and used
on the RX side. Just remove the TX side coax of the relay and install the connector of choice in the
TX hole in the rear panel. Coax it as required.
If you have separate ports and wish to make them common, you can order a relay to be
mounted inside of the transverter. This requires drilling holes in the rear panel. OR—DEMI can do
it for you for a minimum charge.
BUT- a relay may be purchased to be mounted on the outside and it may be wired through
the AUX connector. The relay’s DC power is found on the pad labeled TXON by CR1. This setup is
also the most versatile.
The Standard power unit (25-Watt model) is similar. The common relay is K2 and is
mounted on the circuit board. The common por t is mar ked AN T on t he boar d. The spli t co n nect ions
are the same positions as the High power model. There is no need to remove the relay for the split
connections. Depending on which way you are going, install/uninstall cables and connectors as
required. And as in the high power unit, if you have separate ports, they may be combined with an
external coaxial relay to provide versatility.
Negative Voltage Option: If you have ordered the negative voltage generator, an approximate
-9VDC will be available on the AUX connector pin indicated on the front page. To set this up with
your transceiver, connect the pin and ground to your transceiver’s ALC input. With both the
transverter and Transceiver powered on, measure the output power of the transceiver on
somewhere in the 28 Mhz. band to verify that the ALC circuit within your transceiver is operating
correctly. With the negative voltage applied, there should be minimum power output (less than 1
watt or as low as a few mW’s depending on what type of transceiver it is) With the power meter
still connected, if the transverter is powered off, the transceivers output power should come back to
normal. Be careful if you are using a mW power meter!! If it all checks out, continue with Step 3 of
the Installation section.
You may now connect the RF drive to the transverter and with the transverter switch on, you
may continue to adjust the TXIF drive level in the transverter.
IMPORTANT NOTE: If you are using the ALC (negative voltage generator) circuit and you
desire to use your transceiver for other than transverter use, operating it with the RF/IF cable
connected without the ALC voltage running will damage the transverter. What is suggested is to
place a coaxial relay (SPDT) between the transverter’s IF port and the Transceiver’s RF port. Wire
the relay so that it directs the RF path to the Transverter when energized. Connect the +13VSW
buss and ground to the relay through the AUX connector.
/Built/L144-28rB.doc 8 Rev. B 4/2/2012
When the Transverter is switch on, the relay will direct the RF path of the transceiver to the
transverter and the transverter will apply the negative voltage to the transceivers ALC port. Power
the transverter off will simply switch the transceiver back to normal .
Sequencer: The sequencer configuration may be changed at anytime. If it was specified to be
utilized, the transverter is connected to the 4th and last step of the sequencer. It is wired to the #4
point on the circuit boar d in the sequencer section. This is a “LOW” on transmit. The other
connections are indicated on the front page and wired to the AUX connector. The reasoning is:
Step 1 +12VDC on RX for a preamp @ 500 mA maximum
Step 2 +12VDC on TX for a TR relay (around the preamp) @ 500 mA max imu m
Step 3 Ground on TX to key a power amplifier. Sinks 100 mA maximum
Optional Sequencer Connections:
Step 1 and 2. They can be connected to switch higher DC voltages. The DC voltage is applied to
the DC1 and DC2 connections on the board (30VDC maximum).
Step 2 TL2 is a secondary connection to the second step. It is a “LOW” on transmit. It can be
used to drive a relay or key an amplifier but an external isolation device should be utilized. It will
sink 100 mA maximum
Step 3 and Step 4. They have secondary outputs that are both “High” on transmit. They are
labeled PH3 and PH4. These should be isolated from devices that require high currents and are
intended to drive low current devices or Pass transistors or FETs. They will source 5mA.
For mast mount LNA operation with the basic transverter or with an external high power
amplifier, all tests should be done without RF applied. Verify that the switching is completed in your
desired sequence and gradually add in external components as verified. The last should be the
transverter’s RF applied. All testing can be done without coaxial cables connected. Connect the
transverters IF or TXIF cable last.
The transverter’s sequencer may be by-passed to eliminate switching time delays but is only
recommended if the transverter is to be used without any other system components such as LNAs
or power amplifiers. In this case the external PTT input of the transverter may be connected
directly to the transverter’s PTT input (see component placement document) near C100 (PTT-H) or
C102 (PTT-L) bypassing the sequencer.
Relative Power Meter: The bar graph display is a relative power meter and is driven by the
directional coupler and RF detector circuit found in the Low pass filter section of the board (CR11,
R76,R75,C108) RF is detected and converted to DC voltage and conducted to the Bar graph
display on the front panel. If you find that you operate the transverter at any other level than what
we have calibrated it to (either 25 or 50 watts = 9 bars) you may change it by adjusting VR1 on the
display board.
Other Adjustable Circuits: Other adjustments that may be made are the LO and RX front
end. The Local Oscillator (LO) frequency may be adjusted through the hole on the Can covering
the LO on the transverter. C3 is accessible and may be adjusted with a small blade screwdriver.
Frequency may be monitored at the junction between C29 and M1. Adjust as desi red! Be sure the
transverter has been “ON” for at least 15 min before measuring frequency. Frequency will shift
over time so adjustment is expected.
The Receiver front end (the FET Circuit) should not need adjustment. It is aligned and
tested into a 50-ohm test setup and optimized on a Noise figure meter. No, you can’t screw it up
/Built/L144-28rB.doc 9 Rev. B 4/2/2012
R1 1K
R23 470
R40 220
R55 10K
R70 10K
R2 470
R26 24
R41 10K
R56 10K
R71 10K
R3 470
R27 5.6
R42 10K
R57 10K
R72 1M
R4 1.5K
R28 51
R43 470
R58 1M
R73 10K
R5 100
R29 51
R44 10K
R59 10K
R75 100
R6 51
R30 51
R45 220K
R60 220
R76 51
R7 100
R31 12
R46 1M
R61 10K
R77 1K
R8 470
R32 51
R47 10K
R62 10K
R78 220
R9-R15 NA
R33 1K
R48 10K
R63 1M
R81 5.6K
R17 470
R34 330
R49 1K
R64 10K
R82 5.6K
R18 39(1210)
R35 220
R50 5.6K
R65 220
R84 5.6K
R19 470
R36 1K POT
R51 5.6K
R66 10K
R20 330
R37 220
R52 22K
R67 10K
R21 150 ½ LEAD
R38 1K POT
R53 470
R68 1M
R22 51
R39 220
R54 10K
R69 10K
C1 1000
C41 1000
C64 2-6pF
C90 1000
C2 0.1µF
C42 1000
C65 0.75
C91 1000
C3 4 piston
C43 1000
C66 0.1 µF
C92 1000
C4 1000
C44 1000
C67 0.1 µF
C93 1000
C5 18
C45 1000
C68 1000
C94 10
C6 33
C46 1000
C69 0.1 µF
C95 1000
C7 0
C47 0.1 µF
C70 36
C96 1000
C8 0.1 µF
C48 0.1 µF
C71 12
C97 1000
C9 0.1 µF
C49 1000
C72 1000
C98 0.1 µF
C10 1.0 µF T
C50 1000
C75 1.0 µF T
C99 10 µF T
C11 1000
C51 0.1 µF
C76 0.1 µF
C100 1000
C12 1000
C52 100
C77 0.1 µF
C101 47 µF T
C24 1000
C53 100 µF E
C78 1000
C102 1000
C25 33
C54 27
C79 1000
C103 22 µF T
C26 39
C55 33
C80 1000
C104 10 µF T
C27 33
C56 27
C81 56
C105 10 µF T
by “Tweaking” it but unless you experience instabilities or outside interference, no adjustment
should be necessary unless the FET is replaced.
All filters are aligned by the manufacture for input/output match and pass band ripple.
Adjustments are not recommended or required. Its rare to have a failure of a passive component
unless excessive “tweaking” has occurred.
Synthesizer Installation: This is the newest option available. If installed, there will be a LOC LED
on the front panel. The option will be if you have the dual oscillator or not. If so there will be center
off power switch. If toggled up, it is the standard Oscillator. If the switch is down, it powers the
Synthesizer.
DEM 144-28 COMPONENT LIST
Resistors (R) values are in Ohms and chips unless otherwise specified. “LEAD” = Leaded Resistor.
All capacitors (C) are in pF and are chip unless otherwise specified. “E” = Leaded Electrolytic,
“T” = chip Tantalum
/Built/L144-28rB.doc 10 Rev. B 4/2/2012
C28 1000
C57 1000
C82 150
C106 10 µF T
C31 1000
C58 100
C83 150
C107 10 µF T
C32 0.1 µF
C59 0.1 µF
C85 150
C108 1000
C34 1000
C60 1.0 µF T
C86 56
C112 100 µF E
C35 1000
C61 0.1 µF
C87 1000
C115 22 µF T
C39 1.0 µF T
C62 1000
C88 1000
C121 3
C40 0.1 µF
C63 2-6pF
C89 0.1 µF
C158 100 ATC
L1 8 Turns PW
L12 1.0 µH
L21 1.0 µH
L2 330
L13 3 Turns #24 3/16” dia HW
L22 330
L3 1.0 µH
L14 5 Turns #24 3/16” dia HW
L23 150
L4 1.0 µH
L15 5 Turns #24 3/16” dia HW
L24 220
L7 56
L16 3 Turns #24 3/16” dia HW
L25 150
L8 120
L17 8 Turns small PW
L26 330
L9 120
L18 330
L27 330
L10 56
L19 120
L30 1.0 µH
L11 1.0 µH
L20 27
CR1 1N4000
IC2 PHA-1
Q8 MJD31
CR2 HSMP3814
IC3 MAR3
Q9 PMBT3904
CR3 MPN3404
IC4 MAV11
Q10 MJD32
CR4 MPN3404
IC5 SAV33 OR SAV36
Q11 PMBT3904
CR5 1N914 OR 4148
IC6 PHA-1
Q12 PMBT3904
CR6 1N914 OR 4148
IC7 MAR6
Q13 PMBT3904
CR7 HP2800
IC8 LM393
Q14 MJD31
CR8 HP2800
IC9 LM324
Q15 PMBT3904
CR9 MMBD914
IC10 7660
Q24 PMBT3904
CR10 1N4000
K1 G5V or D2n
Q26 PMBT3904
CR11 HP2800
K2 G6Y
VR3 78L05
CR12 MMBD914
K3 G6Y
VR4 78M05
CR13 MMBD914
M1 SYM18H
VR5 78S09
CR14 1N4000
Q1 2N5179
Y1 116.0000
CR21 MMBD914
Q2 2N5179
PTC-50 Thermistor
F2 144-3
Q5 PMBT3904
F3 144-2
Q6 FPD750
F4 144-2
Q7 PMBT3904
All inductors (L) are in ηH and 1008 chip unless otherwise specified. “PW”=pre-wound
“HW”=hand-wound using enamel wire
Solid State, Relays and Filter Components
/Built/L144-28rB.doc 11 Rev. B 4/2/2012
BAR1 BAR GRAPH DISPLAY
IC1 LM3914
C1 1000 DISC CAP
R1 2.7K 1/4W RESISTOR
C2 100µF ELECTROLYTIC CAP
VR1 10K POTENTIOMETER
X
X
X
1
+DC
GND
Power Meter
C3 0.1µF DISC CAP
/Built/L144-28rB.doc 12 Rev. B 4/2/2012
144MHz and 222MHz
Transverter Schem atic
02/2012
/Built/L144-28rB.doc 13 Rev. B 4/2/2012
VHF-UHF Transv erter
6/30/2010
/Built/L144-28rB.doc 14 Rev. B 4/2/2012
OPTION
x x
x
X
50 Ohm Load OPTION
NTC
XX
XX
X
X
X
X
X
X X
XX
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X X X
X
X
X
X X X
X X X
X
X
144MHz and 222MHz Transverter Assembly
02/2012
X
X
/Built/L144-28rB.doc 15 Rev. B 4/2/2012
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