DEM Part Number 3456-144_____
9 cm Transverter Serial Number________
Specifications
Frequency: 3456.100 MHz. = ________ w/ A32 Synthesizer Installed
Noise Figure and Gain: 1.9 dB nom. > 17 dB Gain
Power Out: 20 mW 1 W Other_____________
DC Power Requirement: 10 - 15.5 VDC @ 1 Amp
IF Option: Common or Split
IF Drive Level Requirement Option: 10 mW 1-10W Other_____________
Keying Option: PTT - to ground TTL - Positive Voltage
Aux. Connection Output Option: Ground on TX + Voltage on TX_____________
TR Switching Option: None Installed Supplied
Operating Instructions:
This DEM 3456-144 transverter is a combination of circuit boards designed by Down East
Microwave Inc. All circuitry operates from a internal 9 VDC Regulated supply which makes it an
ideal portable rig or it can be easily implemented into an existing home station. Please review all
options installed in this transverter before interfacing to a standard 2 Meter IF rig. Interfacing can
be simplified by using one of the various interfacing options available from DEMI or simply
configure your 2M IF rig yourself to correspond with the options installed in the transverter. If you
are unsure of the options installed or of the correct way to interface your 2M IF rig, please consult
DEMI to avoid unnecessary damage to your transverter.
A block diagram is supplied to show the DC wiring of the transverter and the interfacing of
the various circuit boards used in the transverter. This is provided for information and location of
adjustment points to aid in your station integration. This will also aid you if you decide to add a
pre-amp, power amp, T/R switch or sequencer to your system or to install or disable the various
available options. Schematics and circuit board diagrams are also provided for all of the internal
electronics.
Once all interfacing is complete, operation is simple. Please note frequency calibration
listed on the top of this document. Remember the transverter should always be “hard-keyed”. It is
not RF sensed. If your 2M IF rig does not have an external keying line (Push to Talk to Ground,
PTT or Positive Voltage on Transmit, TTL) you will need to install one. You should consult your
manual or the manufacture for details.
Output power levels, receive gain and frequency may be adjusted internally by removing the
top four screws and opening the cover. Be careful because the local oscillator is attached to the
top cover and is connected to the main transverter board by coax and DC power connection.
/Built/3456asem.doc 1 Rev. B 8/2/10
TXIF RXIF
Common IF
TXRF +VTX PTT TXRF 13.8V RXRF
PCB
Mounting
Plate
Rear Panel Diagram
The 1 watt output version will have a extra SMA connector installed. The TXRF connector will be
mounted by the RXRF connector so that a common SMA type relay may be connected to perform
the TR function. The connector in the old TXRF position will be a dummy connector and will not be
connected to any circuitry.
Enclosure and PCB Mounting
MICR O LO PCB
or A32 PCB
9V DC
(Ground Pl ane )
Trimmer
Switch
LED
TC
PCB
RX
TX
LO ou tput
COAX
3456 PCB
Mounted on
Stand-Offs
Capacitor
SM A
RCA
BN C
RCA
SMA
Enclosure and PCB Mounting
/Built/3456asem.doc 2 Rev. B 8/2/10
TX RF
34 56 Tra nsve rt er PCB
RX RF
1104 MHz. LO
LO
+TX
+R X
+9 VDC
2M IF
10W Max.
M2 M1
RX IF
TC
+13.8VDC
TX IF
Wiring Block diagram
3456 Transverter Board Parts List
All components are Surface Mount components unless otherwise noted.
C1 8.2 ρF ATC C12 0.1 μF C25 0.1 μF R9 10 Ω
C2 0.1 μF C13 0.1 μF C26 10 ρF R10 10 Ω
C3 10 ρF C14 10 ρF C31A 10 ρF R11 130 Ω
C4 0.1μF C15 0.1 μF R1 10 Ω R13 130 Ω
C5 0.1 μF C16 100 ρF R2 51 Ω R18 130 Ω
C6 100 ρF C17 0.1 μF R3 150 Ω R20 130 Ω
C7 10 ρF C18 10 ρF R4 130 Ω
C8 0.1 μF C19 0.1 μF R5 51 Ω
C9 10 ρF C20 0.1 μF R6 130 Ω
C10 0.1 μF C21 0.1 μF R7 130 Ω
C11 10 ρF C22 100 ρF R8 150 Ω
U1 MGA86576
U2 ERA-1
U3 ERA-1
U4 ERA-1
U5 ERA-2
3456-144 PA SECTION
C27 0.1 μF
C28 10.0 μF
C29 0.1 μF C34 0.1 μF R22 51 Ω
C30 10 pF
C31B 10 pF
C32 10 pF R19 10K pot Q1 FLL 177
C33 10 pF
R21 51 Ω
C35 10.0 μF R23 1Ω, 1Watt
C36 10.0 μF
IC1 7660
+LO
U6 ERA-1
U7 ERA-1
U11 ERA-4
CR1 MA4E2054
CR2 MA4E2054
Optional ERA-1
“ 200 Ω
“ 130 Ω
2- sets of 2-56 screw & nut
/Built/3456asem.doc 3 Rev. B 8/2/10
Operating and use tips:
1. You will need to hard-key this transverter. It is not RF senesced! If you wish to have your
transceiver key the transverter, you will need to use the auxiliary contacts or a positive voltage
on transmit generated by your IF transceiver.
2. The transverter will accept a maximum IF drive level of what is indicated on the front page. If
the 10 watt IF drive version is ordered, a maximum of 25 watts may be applied momentarily
without causing damage to the transverter. If you wish to use a transceiver with an output
power greater than 10 watts, you will need to supply additional attenuation. A receive IF gain
stage may be added to the TC board to compensate for the additional attenuation. See that
enclosed document for details.
3. RX and TX levels may change slightly after adjustments when the enclosure is re-assembled.
4. Be sure to use high quality coax for all connections
5. This unit may be mast mounted but it is not weatherproof. Simple protection from the rain is all
that is required.
/Built/3456asem.doc 4 Rev. B 8/2/10
DEM TC
DEM TRANSVERTER CONTROL
The DEM Transverter Control (DEM TC) is the circuit board that controls all transverter
functions in the DEMI 2.3 GHz. -10 GHz. transverters. It was designed with many options and
depending on the configuration you have ordered (see configuration page of main transverter
document), the options may or may not be enabled in your transverter. This document will cover
all of the features available for understanding and make it possible to change the configuration at
any time to suit your requirements.
Circuit Description:
The DEM TC circuit board is mounted in the front of the transverter. It includes the DC
power switch and both the “Power On” and the “Transmit On” LED’s. The TC contains a 1.5 amp,
9 Volt regulator that supplies the transverter with all of the regulated DC voltage it requires and
allows some head room for other external circuits. The TC controls all of the IF switching functions
utilizing a high isolation RF relay that is rated through 1 GHz. It allows the use of any frequency of
IF up to 1300 MHz. On transmit it will allow the use of up to a maximum of 10 watts of drive
depending on configuration. The TC also incorporates adjustable attenuators for both transmit and
receive and has a provision for adding additional receive IF gain. The TC allows either a PTT High
or Low for keying the transmit and receive circuits. Another feature included on the TC circuit
board is a 24 Volt relay driver designed to operate most SMA relays used for Transmit and
Receive switching of the RF frequencies. This circuit may not work with certain types of relays but
will operate with any SMA relay supplied by DEMI. Other options include different auxiliary DC
switching schemes, keying the transverter through the IF coax, and supplying PTT keying signals
to external equipment. Connection and use of each circuit is explained below. Refer to schematic
and component list for all component designations.
RXIF Gain and Adjustment:
The installation of the receive IF gain stage is the most asked about device in the
transverter. If the transverter is to be installed at the antenna with a long run of coax for the IF line,
you may wish to install IC1. Understand that installing this gain stage will not improve the system
noise figure and in most cases it will slightly degrade it. If you wish to improve the system noise
figure, you should add a LNA at the RF frequency. Then depending on the gain of the additional
RF LNA, you may not need the RXIF gain stage even if the transverter mast mounted. If you wish
to install IC1, refer to the component placement to determine where it is installed along with its bias
resistor R9. Any low frequency MMIC may be used but select it for the correct amount of gain
required. Also consider the noise figure unless you have a RF LNA in the system. Select the
value of R9 for the MMIC to be used for 13.8VDC operation. To bypass the gain stage, install a
leaded 120pF capacitor in place of IC1. Keep the leads short.
The RXIF gain can be adjusted with R7. There should be approximately 20 dB of range.
With your system completely connected, R7 may be adjusted to an acceptable level determined by
your ear. For best results, keep the gain to a minimum. Only a slight noise increase should be
noticed by cycling the power switch of the transverter. If your “S” meter of your IF radio is at half
scale, you have lost half of the dynamic range of your system. For the same reasoning, adding the
gain stage and then adjusting the RXIF to maximum will degrade the dynamic range further.
(All functions mentioned may or may not be enabled in your transverter)
/Built/3456asem.doc 5 Rev. B 8/2/10
TXIF Drive Level and Adjustment.
The TXIF drive level adjustment (R2) has approximately 20 dB of range. Depending on the
configuration ordered, this adjustment range may not be acceptable. If so the fixed attenuator may
need to be installed, removed, or adjusted. If you wish to use less than 50 milliwatts of IF drive
power, install a short jumper wire in the R4 position and remove the large 50 ohm termination that
may be installed on the front panel. If you wish to use up to 2 watts, install R4 as shown with the
large 50 ohm termination. If you plan to use 1 - 10 watts of IF drive, install a 1pF capacitor in the
R4 position with the 50 ohm termination. If you need to experiment with other drive levels, any
combination of variable capacitor or resistor may be used in the R4 position. You may also adjust
the values of R1 and R3 as needed. Input power to the TXIF adjustment is dependent on the
attenuation installed on the C3 side of the K1 relay. The 50 ohm load resistor is designed to
handle 35 watts with proper heat sinking. When mounted to the front panel of the transverter, it
will not tolerate more than 10-12 watts reliably for a long period of time. You may experiment with
external heat sinking if you desire. External attenuation may also be used in the transceive path.
Remember that the added attenuation is also on the receive signal but may be overcome by the
additional gain of the RXIF gain stage. The level then may be adjusted with the RXIF adjustment.
Split Transmit and Receive or Common IF Configuration:
If you wish to use your transverter with separate TX and RX ports, first remove C3 and C5.
Then attach coax from the IF connectors to the corresponding TXIF and RXIF connections at the
C3 and C5 locations. If you are converting a split IF to a common IF, C3 and C5 may or may not
be already installed. Select the coax you wish to keep as the common and connect it to the
common input of K1.
PTT-H and PTT-L
The TC has the option of either using a PTT-H or PTT-L keying circuit. The PTT-H requires
+1.5 to +18VDC to activate it and will sink up to 2 mA. If using this circuit, be certain that the sink
current will not exceed your transceivers rating. The PTT-L circuit requires a connection to ground
to be activated. It is connected to the K1 relay and will source up to 25 mA to ground when keyed.
If this exceeds your transceivers rating you may modify the TC as shown in our design note DN0??
Found in our library on our web site or call for a copy.
PTT Keying Through the IF Coax:
Some transceivers such as certain models of the Yeasu FT290 supply a positive voltage on
it’s RF output connector during transmit or receive. This voltage may be used for keying the
transverter. After verifying or modifying your transceiver for this function, the transverter may have
the option installed. Select a choke of 1.0 μh or larger and install it in the L1 position of the TC.
Then connect a short wire jumper from the DC side of L1 to the PTT-H connection. When the
transceiver is keyed, the voltage in the coax will key the PTT-H of the transverter. This is the most
fool proof connection of the PTT line that can be made with any transceiver and is highly
recommended by DEMI.
If the PTT-L connection is connected to the PTT connector, it will not affect the operation of
the system. Just do not key both lines at the same time! If you will never use it, it may be
disconnected and the external connector may be used for any other auxiliary connections.
/Built/3456asem.doc 6 Rev. B 8/2/10
+DC Switching Functions:
Relay K2 controls all of the +DC switching functions in the transverter. One side of the relay
switches the raw +DC supply voltage to the transverter and the other side switches the regulated
+9 volts. There are extra connection holes on the PCB if you require any additional switched
voltage. Be sure not to exceed the 1.5 amp limit on the 9 volt regulated supply. The transverter’s
current drain is listed on its configuration page and allow for some overhead when the oscillator is
not warmed up.
The switched voltages may be used for external LNA’s, switching circuits for power
amplifiers or relays. You may need to add an extra hole for a connector if the AUX connector is
used. Be sure to fuse any external connections. The relay’s contacts (K2) are rated for 3 amps.
24 Volt Relay Driver:
The TC is designed with a 24 Volt relay driver. A brief explanation of the circuit is as
follows. When the TC is in the receive mode, a 330 μF capacitor is charged to the raw input
voltage of the transverter (12-14 VDC). When the PTT circuit is activated, K3 switches this
charged capacitor in series with the TXON voltage and outputs a brief spike of 24-28 VDC at the
+R connection on the TC board. Depending on the current drain of the connected circuit (or relay),
the charged capacitor bleeds off down to the raw input voltage of the transverter. The spike is
enough to energize most SMA relays and the raw transverter voltage is enough to keep the relay
energized. This circuit will not work with all relays but will operate with all relays supplied by DEMI
in the optional WTR kit. If you wish to use a relay with a higher current drain, the 330 μF capacitor
may be increased. Just be sure that the relay being used will stay energized with +12 VDC. This
circuit will not operate latching relays unless additional circuitry is installed.
PLEASE NOTE! Even though this connection will bleed down to the raw voltage of the
transverter, the circuit should never be used on any electronic circuit that will not tolerate a
+28VDC input! It will damage most +12VDC circuits. It will also not operate any circuit requiring
voltage greater than the transverter’s supply voltage other than a relay.
If a switched +VDC is required, move the wire from the +R connection (if installed) to either
the +VTX, +RX, +9, +13RX, +13TX, or +13.8SW. Refer to the schematic for their functions.
RF Sensing Transverter Keying
The TC is not designed to be a RF sensed switch. It has 3 relays and it may be connected
to external mechanical relays. If any RF sensing scheme is added to the circuit, it will cause
excessive relay chatter that will not only ware out the relays prematurely, but could cause other
failures to external preamplifiers and or power amplifiers if used in your system. RF sensing
circuits are not recommended with any circuit that contain mechanical relays at RF frequencies!!
/Built/3456asem.doc 7 Rev. B 8/2/10
DEM TC Component List
C1 0.01 μF C10 2.2 μF elect.
C2 0.01 μF C11 2.2 μF elect. R1 220 Ω R10 5.1KΩ
C3 0.01 μF C13 330 μF elect.
C4 0.01 μF
C5 0.01 μF
C6 0.01 μF
C7 0.01 μF
C8 0.01 μF
C9 100 μF elect. L1 1.0 μh o R8 220 Ω
n To by-pass IF gain stage, install 120pF in place of IC1.
o L1 is used with transceivers that have + DC voltage on RF line during transmit
p Depending on the drive level used, R4 may be replaced with a short, a 1pF capacitor, or a
variable capacitor. See text for description.
D1 -D6 1N4000
IC 1 MAR6 n
K1 G6Y relay
K2 G5V relay
K3 G5V relay R7 1K pot
Q1 PN2222
R2 1K pot
R3 220 Ω R12 330 Ω
R4 220 Ω p
R5 1K Ω
R6 220 Ω 50 Ω load
R9 330 Ω
R11 5.1KΩ
2 - Red LED
VR1 78S09
1 ρF p
/Built/3456asem.doc 8 Rev. B 8/2/10
TX
RX
8
D
7
D
/Built/3456asem.doc 9 Rev. B 8/2/10
TX
J
ADJUST
TX
X
D
7
D
8
XX
RX
Caution:
Lift
Leads
RX
AD
LEDS
UST
/Built/3456asem.doc 10 Rev. B 8/2/10
PA Section
+9
+
C28
CR-2
TX IF
C22
3
R19
U1
5
U7
C36
+
4
8
2
+
C35
R22
U6
C31B
C33C34
Q1
C30
TX HIGH
R23
VTX
C29
U11
C32
R21
C27
C31A
TX LOW
RX IF
CR-1
C6
R13
C20C21
+VTX
U2
R4
R3
R10
C17
R2
C18
U1A
C25
R1
R11
U1
R20
R18
C19
C1
+VTX
C26
RX
C5
C4
C3
C2
+VRX
R5
C7
U3
C9
U4
R9
U5
C16
LO IN
C8
R6
C13
C12
R7
C11
C10
R8
C15
+9
C14
3456-144 TRANSVERTER SCHEMATIC
/Built/3456asem.doc 11 Rev. B 8/2/10
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