Ritron RIT11-450 Two Way Radio Transceiver Module User Manual Instruction Manual
Ritron Inc Two Way Radio Transceiver Module Instruction Manual
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Instruction Manual
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 1 of 32
TYPE OF EXHIBIT:INSTRUCTION BOOK (PRELIMINARY)
FCC PART:2.983 (d) (8)
MANUFACTURER:RITRON, INC.
505 West Carmel Drive
Carmel, IN 46032
MODEL:DTX-454
TYPE OF UNIT:UHF-FM Transceiver
FCC ID: AIERIT11-450
DATE: February 2, 1999
Preliminary Instruction Book follows.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 2 of 32
RITRON, INC.
RITRON MODEL DTX-454
PROGRAMMABLE FM TRANSCEIVER
MODULE
MAINTENANCE
& OPERATING
MANUAL
FOR USE ONLY BY AUTHORIZED SERVICE/MAINTENANCE PERSONNEL
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 3 of 32
DTX454 SPECIFICATIONS
GENERAL
FCC Identifier AIERIT11-450 (pending)
FCC Rule Parts 22, 74, 90, 95
Frequency Range 400-420 MHz *
420-440 MHz *
430-450 MHz *
450-470 MHz
470-490 MHz *
490-512 MHz *
Number of Channels 8
Transmit/Receive Spacing 20 MHz max.
Mode of Operation Simplex or Half Duplex
Frequency Control PLL Synthesizer
Channel Increment (Synthesizer step size) 5/6.25 kHz
Emissions Bandwidth
Narrow Mode 11 kHz
Wide Mode 16 kHz
Frequency Stability (-30 to +65C) 1.5 ppm
Supply Voltage
6 watt version
w/o internal regulator 7.5 VDC
w internal regulator 11-16 VDC
10 watt version 11.5 to 15 VDC
RF Input/Output Connector BNC
Power/Data Interface 15 pin subminiature D type
Operating Temperature -30 to +65 C
Maximum Dimensions (L x W x H) 3.6” x 2.3” x 1.0” including connectors
Weight 6 oz.
* Not Available Yet
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 4 of 32
TRANSMITTER
Operating Bandwidth 20 MHz
RF Output Power
6 watt version 1 to 6 watts, adjustable
10 watt version 1 to 10 watts, adjustable
Duty Cycle 5 to 100 % depending upon heatsink and
power level
RF Load Impedance 50 ohms
Modulation Distortion (per TIA/EIA 603) 5 % max.
Modulation Frequency Response (+1/-3 dB ref 1 kHz)
At MIC IN (ref pre-emphasis curve) 50 Hz to 2500 Hz
At AUX IN w/o pre-emphasis 50 Hz to 2700 Hz
Transmitter Attack Time:
To within 2.5 ppm final frequency 10 ms max.
To within 0.5 ppm final frequency 15 ms max.
Spurious and Harmonics -20 dBm max.
FM Hum and Noise (per TIA/EIA 603)
12.5 kHz channel operation 40 dB min.
25 kHz channel operation 45 dB min.
Group Delay Variation (Within Frequency Response) 5 us max.
Current Drain
6 watt version at 7.5 VDC supply
1 watt 1.0 A max.
6 watts 2.4 A max.
10 watt version at 13.7 VDC supply
1 watt 0.7 A max.
10 watts 2.4 A max.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 5 of 32
RECEIVER
Operating Bandwidth 20 MHz
Sensitivity (12 SINAD w de-emphasis) 0.30 uV (-117.5 dBm)
RF Input Impedance 50 ohms
Adjacent Channel Selectivity
+/- 12.5 kHz w narrow IF 60 dB min.
+/- 25 kHz w wide IF 70 dB min.
Spurious and Image Rejection 70 dB min.
Intermodulation Rejection 70 dB min.
FM Hum and Noise (per TIA/EIA 603)
12.5 kHz channel operation 40 dB min.
25 kHz channel operation 45 dB min.
Conducted Spurious -57 dBm max.
Receive Attack Time 15 ms max.
Audio Distortion (per TIA/EIA 603) 5 % max.
Audio Response at AUX OUT (+1/-3 dB, ref 1 kHz)
12.5 kHz channel operation 100 Hz to 3.5 kHz
25 kHz channel operation 100 Hz to 5 kHz
Group Delay Variation (Within Frequency Response) 20 us max.
Receive Current Drain 75 mA max.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 6 of 32
DTX-154/454 INPUT/OUTPUT CONNECTOR
Pin Number Name Description Comments
1CS0 Channel Select low bit
2CS1 Channel Select mid bit
3CS2 Channel Select high bit
4MIC IN Microphone Input Input for microphone type signals
to be transmitted. Signals at this
input are pre-emphasized, limited,
and filtered.
5CSN Channel Select
6RAW SUPPLY Power Supply Input Positive Supply voltage input.
7AUX IN Auxiliary Input Wideband input for data.
8AUX OUT Auxiliary Output Wideband output for data.
9PGN IN/OUT Programming I/O External programmer connects
here.
10. CTS Clear to Send Active high when transmitter
can accept modulation.
11. RX MON Monitor Breaks squelch in receive.
12. AUDIO OUT Audio PA Output Output of audio PA.
13. DCD Carrier Detect Carrier detect output.
14. PTT RTS Push to Talk Activates transmitter.
15. GND Ground Negative supply point and
reference for all inputs.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 7 of 32
Pin Number Description
1 CS0-Least significant bit of the channel select lines. Active high 5 volt TTL/CMOS
level.
2 CS1-Mid bit of the channel select lines. Active high 5 volt TTL/CMOS level.
3 CS2-Most significant bit of the channel select lines. Active high 5 volt TTL/CMOS
level.
Channel CS0 CS1 CS2
1 0 0 0
2 0 0 1
3 0 1 0
4 0 1 1
5 1 0 0
6 1 0 1
7 1 1 0
8 1 1 1
0 = Logic low
1 = Logic high
4 MIC IN-Microphone input. This input accepts microphone type input signals for
transmit The signal is amplified, passed through the clipper and the clipper filter and
then to the RF board. This input can be programmed to be disabled (muted) if desired.
5 CSN-When enabled through programming, this input selects between channels 1 and 2.
This input is TTL/CMOS level type input with a logic low required for channel 1 and a
logic high required for channel 2.
6 RAW SUPPLY- The positive supply voltage for the unit is supplied through this pin.
The actual supply voltage required depends upon model type. Ensure that the correct
supply voltage per the given model is used.
7 AUX IN-This is the broadband input for modulation. The gain through this input to the
modulator is programmable as is the use of pre-emphasis. This signal passes through the
clipper and clipper filter.
8 AUX OUT-This is the broadband output of the receiver. The gain from the receiver to
the output is programmable as is the use of de-emphasis. The choice of AC or DC
coupling from the RF board discriminator is also programmable.
9 PGN IN/OUT-Connect via Ritron RPT-PCPK PC Programming Kit to computer for
programming the unit.
10 CTS-Clear-To-Send output from the unit which indicates that the unit is transmitting a
carrier at the correct frequency and power level and is ready to accept an input signal to
be transmitted. This output would normally become active in response to a PTT RTS
(see pin 14 description below) activation. The polarity of this output can be programmed.
The output is active low 5 volt logic with an internal 10 k ohm pull-up to 5 volts. It can
source up to 10 mA when low.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 8 of 32
11 RX MON-This input breaks the squelch on the receiver i.e. allows for monitoring the
channel, even when a signal not strong enough to break squelch is present. Input levels
are TTL/CMOS; polarity may be programmed.
12 AUDIO OUT-This is the output of the audio power amplifier. This output can drive up
to ½ watt in to an 8 ohm load. This output can be enabled and its gain controlled by
programming.
13 DCD-Carrier Detect Output. This output becomes active when a signal strong enough to
exceed the programmed squelch threshold is present. The polarity of this output can be
programmed. The output is active low 5 volt logic with an internal 10 k ohm pull-up to 5
volts. It can source up to 10 mA when low.
14 PTT RTS-Push To Talk/Request To Send. This input commands the unit to transmit.
Input levels are TTL/CMOS; polarity may be programmed.
15 GND-System ground. All signals and voltages are referenced to this input. The negative
side of the power supply should connect here.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 9 of 32
RF BOARD J301 INPUT/OUTPUT
Pin Number Name Description
J102-0 PWR_SET When PC board jumper R185 is installed and R186 omitted (normal
with the loader board connected), the voltage on this pin controls the
RF output power. When R186 is installed and R185 omitted(normal
for stand alone RF board), the RF output power is controlled by R187
on the RF board and this pin has no function. When this pin is used,
the voltage should range between about 1 and 4.5 VDC to vary the
output power from 1 to 5 watts. The relationship between output power
and voltage is non-linear and may vary as a function of operating
frequency. The input resistance at this pin is approximately 15 k-ohm.
J101-1 GND System ground. All voltages are referenced to this point.
J102-2 FB+ Power supply input for the RF PA module. Voltage at this pin depends
upon model and should be either +7.2 VDC +/- 10% or 11 to 16 VDC,
and filtered . Current drain can be as high as 2.5 amperes at maximum
RF output.
J102-3 TX_EN Active high, 5 volt CMOS logic level input used to enable the
transmitter driver stage and PA pin diodes. Timing circuitry exists
on the RF board to ramp the PA power up or down to control keying
spurious outputs.
J102-4 RX_EN Active high, 5 volt CMOS logic level input used to enable the receiver
stages and to set the VCO to the receive frequency range.
J102-5 XCVR_EN Active high, 5 volt logic level input used to enable all stages of the
board except the PA and PA driver stages. This pin can be used to
conserve current consumption in a battery save configuration.
J102-6 MOD_IN Modulation input for the transmitter. The modulating signal must be
superimposed upon a very stable and low noise 2.5 VDC level.
Modulation sensitivity is approximately 14 kHz/V. The input
resistance is approximately 17 k-ohm. Note: The DC voltage at this
pin directly controls the frequency of the unit. Therefore, the DC
voltage must be well regulated and controlled over environmental
conditions.
J102-7 LOCK_DETECTLock detect output of the frequency synthesizer. Output is at 5 volt
logic level with a high level indicating lock.
J102-8 SYN_EN Enable line for loading the synthesizer. Signal is at 5 volt CMOS logic
levels.
J102-9 SYN_DATA Data line for loading the synthesizer. Signal is at 5 volt CMOS logic
levels.
J102-10 SYN_CK Clock line for loading the synthesizer. Signal is at 5 volt CMOS logic
levels.
J102-11 +7.2V +7.2 VDC +/- 10 % input for powering all stages of the radio except
RF PA module. Current drain is approximately 45 mA in receive and
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 10 of 32
100 mA in transmit.
J102-12 RSSI Receive signal strength indicator output. This is a high impedance
output which is used to indicate the presence of a carrier. When R124
is installed (R125 omitted), the output will vary between
approximately 0.5 VDC and 3.0 VDC as the input signal level varies
between –130 dBm and –70 dBm. When R125 is installed (R124
omitted), the output will vary between approximately 2.5 VDC at 0
dB SINAD and 0.5 VDC at 20 dB SINAD. The loading on this output
must be kept above 100 k-ohm.
J102-13 DISC_OUT DC coupled discriminator output. The polarity of this output is
controlled by R131 and R132. For positive polarity i.e. an increase
in carrier frequency causes the DC level to increase, R131 should be
installed and R132 omitted. For negative polarity, R132 should be
installed and R1431 omitted. The output is low impedance with a
modulation sensitivity of approximately 0.5 V/kHz for narrow band
units and 0.25 V/kHz for wide band units. The DC level at this pin
is typically between 2 and 4 volts.
J102-14 VCO_MOD When R179 is installed and R178 omitted (normal with loader board
attached), a signal at this pin will modulate the VCO. When R178 is
installed and R179 omitted (normal for stand alone RF board), theVCO
receives its modulation from the MOD_IN pin and this pin has no
function. This pin is provided to allow the modulation balance to be
controlled through an external board rather than R180 on the RF board.
If this pin is to be used, the DC level should be approximately 5 VDC
and from a low noise source. The DC voltage at this pin does not affect
the transmit frequency. The modulation sensitivity is approximately 20
kHz/V.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 11 of 32
DTX-154/454 SYNTHESIZER LOADING
The following information describes the DTX-154/454 synthesizer programming format. This information
can be used for designing programming software for the DTX-154/454 RF board synthesizer when the
DTX-154/454 Loader board is not used.
Note: The user must obtain FCC Type Acceptance when the Ritron RF board is not used with the
Ritron Loader board in the DTX-154/454 enclosure.
The DTX-154/454 RF board uses a PLL (Phase Locked Loop) frequency synthesizer which compares the
phase of the outputs of two digital frequency dividers. One divider divides the VCO (Voltage Controlled
Oscillator) frequency and the other divides the reference frequency. If the two divided outputs differ in
frequency, an error signal is generated which, after filtering, is used to control the frequency of the VCO.
The net result is that the VCO is locked in frequency to an integer multiple of the reference. To control the
frequency, the divider values must be determined. These values are converted to binary and become part of
four control words which must be loaded to the synthesizer IC for proper operation. The steps for
determining the frequency control part of the control words is as follows:
1. The RF R register counter value is first determined. This integer is the reference oscillator
frequency (14.4 MHz in this product) divided by desired reference frequency. The reference
frequency is 16 times the desired synthesizer step size. Typical step sizes are 5 kHz and 6.25 kHz.
For a 6.25 kHz step size and a 14.4 MHz reference oscillator, the R register counter value would
be 144 decimal. When converted to binary, this value is substituted for the R in the State column
in the RF_R_Register table.
2. The RF N register counter values are then determined. This is accomplished by taking the desired
VCO frequency and dividing it by the desired synthesizer step size value used above. The
resulting integer is converted to binary. The least significant 4 bits become the value for the
FRAC_CNTR. For frequencies below 500 MHz, bit 21 (PRESC_SEL) must be set to 0 with the
next 3 significant bits of the integer used to fill in the 3 least significant bits of RF_NA_CNTR
(bits 6,7,and 8). The two most significant bits of RF_NA_CNTR (bits 9 and 10) are loaded with
0. The remaining bits of the integer are loaded into RF_NB_CNTR (bits 11 through 20). For
frequencies above 500 MHz, bit 21 (PRESC_SEL) must be set to 1 and the 4 bits following the 3
loaded into FRAC_CNTR are used for RF_NA_CNTR with the most significant bit of
RF_NA_CNTR (bit 10) set to 0. The remaining bits of the integer are loaded into RF_NB_CNTR.
3. In transmit, the VCO frequency is equal to the operating frequency. In receive, the VCO
frequency is 43.650 MHz below the receive frequency. When calculating receive values, ensure
that 43.650 MHz is subtracted from the desired frequency before beginning the above calculations.
4. Example:
For a frequency of 461.750 MHz in transmit with a 6.25 kHz step size, the RF_R value is 144
decimal or 0000 0000 1001 0000 binary. The RF_R register would therefore become 1000 0110
0000 0010 0100 0010 (MSB first). The VCO frequency divided by the step size is 73,880 decimal
or 0001 0010 0000 1001 1000 binary. The RF_N register would therefore become 0001 0010
0000 1000 0110 0011 binary. For 461.750 MHz receive, the VCO frequency would be 418.100
MHz, which yields a divider of 66,896 decimal or 0001 0000 0101 0101 0000 binary. The RF_N
register would become 0001 0000 0101 0001 0100 0011 binary.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 12 of 32
The four registers of the synthesizer, their bit definitions, and required states are shown below:
IF-R Register
Bit Name State Comments
23 OSC 0External reference oscillator
22 FRAC 16 1Fraction = 16
21 FoLD 0RF digital lock detect
20 FoLD 1RF digital lock detect
19 FoLD 0RF digital lock detect
18 CP_GAIN_8 XDon’t care (1=IF charge pump current=8X)
17 IF_PD_POL XDon’t care (1=positive polarity on IF charge pump)
16 IF_R_CNTR XDon’t care (IF reference divider MSB)
15 IF_R_CNTR XDon’t care
14 IF_R_CNTR XDon’t care
13 IF_R_CNTR XDon’t care
12 IF_R_CNTR XDon’t care
11 IF_R_CNTR XDon’t care
10 IF_R_CNTR XDon’t care
9IF_R_CNTR XDon’t care
8IF_R_CNTR XDon’t care
7IF_R_CNTR XDon’t care
6IF_R_CNTR XDon’t care
5IF_R_CNTR XDon’t care
4IF_R_CNTR XDon’t care
3IF_R_CNTR XDon’t care
2IF_R_CNTR XDon’t care (IF reference divider LSB)
1 0Identifies register
0 0 Identifies register
Notes:
1. The IF part of the dual synthesizer is not used. Only those bits which affect the RF part of the
synthesizer have importance.
IF_N Register
Bit Name State Comments
23 IF_CNT_RS 0Normal operation
22 PWDN_IF 1IF powered down
21 PWDN_MODE 0Asynchronous power down
20 Fastlock 1Fastlock enabled
19 Test 0Test bit-should be set to 0
18 OUT_1 XDon’t care in fastlock mode
17 OUT-0 XDon’t care in fastlock mode
16 IF_NB_CNTR XDon’t care (IF N register B counter MSB)
15 IF_NB_CNTR XDon’t care
14 IF_NB_CNTR XDon’t care
13 IF_NB_CNTR XDon’t care
12 IF_NB_CNTR XDon’t care
11 IF_NB_CNTR XDon’t care
10 IF_NB_CNTR XDon’t care
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 13 of 32
9IF_NB_CNTR XDon’t care
8IF_NB_CNTR XDon’t care
7IF_NB_CNTR XDon’t care
6IF_NB_CNTR XDon’t care
5IF_NB_CNTR XDon’t care (IF N register B counter LSB)
4IF_NA_CNTR XDon’t care (IF N register A counter MSB)
3IF_NA_CNTR XDon’t care
2IF_NA_CNTR XDon’t care (IF N register A counter LSB)
1 0 Identifies register
0 1 Identifies register
Note:
1. The IF part of the dual synthesizer is not used. Only those bits which affect the RF portion of the
synthesizer and the bits to shut down the IF portion are used.
RF_R Register
Bit Name State Comments
23 DLL_MODE 1Delay line loop calibration enabled
22 V2_EN 0Charge pump voltage doubler not enabled
21 CP_8X 0Charge pump current MSB
20 CP_4X 0Charge pump current MSB-1
19 CP_2X 0Charge pump current LSB+1
18 CP_1X 1Charge pump current LSB
17 PF_PD_PO 1Charge pump polarity is positive
16 RF_R_CNTR RRF R register counter MSB
15 RF_R_CNTR RRF R register counter
14 RF_R_CNTR RRF R register counter
13 RF_R_CNTR RRF R register counter
12 RF_R_CNTR RRF R register counter
11 RF_R_CNTR RRF R register counter
10 RF_R_CNTR RRF R register counter
9RF_R_CNTR RRF R register counter
8RF_R_CNTR RRF R register counter
7RF_R_CNTR RRF R register counter
6RF_R_CNTR RRF R register counter
5RF_R_CNTR RRF R register counter
4RF_R_CNTR RRF R register counter
3RF_R_CNTR RRF R register counter
2RF_R_CNTR RRF R register counter LSB
1 1 Identifies register
0 0 Identifies register
Notes:
1. CP_1X through CP_8X bits determine the magnitude of the charge pump current. The values
range from 100 uA for 000b to 1.6 mA for 111b in 100 uA steps. The values shown are for 200
uA. For fast loading algorithms, this current may have to be changed dynamically.
2. The RF_R_CNTR bits are determined by the desired reference frequency which is determined by
the synthesizer step size.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 14 of 32
RF_N Register
Bit Name State Comments
23 RF_CNT_RST 0Normal operation
22 PWDN_RF 0Powered up
21 PRESC_SEL 0Prescaler modulus set for 8/9 for 250-500 MHz operation
20 RF_NB_CNTR BRF N register B counter MSB
19 RF_NB_CNTR BRF N register B counter
18 RF_NB_CNTR BRF N register B counter
17 RF_NB_CNTR BRF N register B counter
16 RF_NB_CNTR BRF N register B counter
15 RF_NB_CNTR BRF N register B counter
14 RF_NB_CNTR BRF N register B counter
13 RF_NB_CNTR BRF N register B counter
12 RF_NB_CNTR BRF N register B counter
11 RF_NB_CNTR BRF N register B counter LSB
10 RF_NA_CNTR ARF N register A counter MSB
9RF_NA_CNTR ARF N register A counter
8RF_NA_CNTR ARF N register A counter
7RF_NA_CNTR ARF N register A counter
6RF_NA_CNTR ARF N register A counter LSB
5FRAC_CNTR FRF fraction counter MSB
4FRAC_CNTR FRF fraction counter
3FRAC_CNTR FRF fraction counter
2FRAC_CNTR FRF fraction counter LSB
1 1 Identifies register
0 1 Identifies register
Note:
1. The bits for the RF_NB_CNTR, RF_NA_CNTR, and FRAC_CNTR are determined by operating
frequency and reference frequency.
2. To conserve power, the synthesizer can be powered down with the PWDN_RF bit.
The four registers are loaded using pins 8, 9, and 10 of J102. Pin 8, SYN_EN is the synthesizer enable line.
Pin 9, SYN_DATA is the data line, and pin 10, SYN_CK is the clock line. Data is clocked into the
synthesizer most significant bit first and must be valid and stable on the rising edge of the clock. The clock
must be high a minimum of 10 ns and must be low a minimum of 50 ns before the next pulse. During
loading, the synthesizer enable line must be held low. At the conclusion of loading a register, the enable
line must be taken high for a minimum of 50 ns. The user should wait a minimum of 5 ms after board
power up before loading the synthesizer. This gives the power supply regulators time to reach stable
voltages. More complete information regarding the synthesizer IC may be obtained by referring to the
National LMX2352 data sheet.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 15 of 32
INTRODUCTION
General
The RITRON DTX-454 is a programmable 2-way radio module which operates in the UHF professional
FM communications band. Each of eight channels can be programmed to contain a unique set of operating
frequencies and settings.
The DTX-454 module is made up of two PC boards, an RF board and a Loader board. These two boards
are enclosed in a metal case with two connectors on one end: a 50 ohm BNC connector for connection to an
antenna and a DB-15 sub-miniature connector for power and control input/output.
FCC Regulations
Licensing
The FCC requires that the radio owner obtain a station license for his radio before using the equipment to
transmit, but does not require an operating license or permit. The station licensee is responsible for proper
operation and maintenance of his radio equipment, and for ensuring that transmitter power, frequency and
deviation are within the limits specified by the station license. This includes checking the transmitter
frequency and deviation periodically using appropriate methods.
Type Acceptance
The unit is type accepted for transmission of either voice or data signals when aligned according to the
alignment procedure for the proper bandwidth and when operated as a complete unit in the metal case.
Operation of the RF board as a stand-alone unit or in combination with any other equipment, in any mode
outside the alignment procedure, or with the clipper filter electronically disabled will require the filing of a
new type acceptance application with the FCC by the user.
Safety Standards
The FCC (with its action in General Docket 79-144, March 13, 1985) has adopted a safety standard for
human exposure to radio frequency electromagnetic energy emitted by FCC regulated equipment.
RITRON follows these safety standards and recommends that you observe them also:
DO NOT operate radio equipment near electrical blasting caps or in an explosive atmosphere.
DO NOT operate any radio transmitter unless all RF connectors are secure and any open connectors are
properly terminated.
DO NOT operate the transmitter of a fixed radio (base station, microwave, rural telephone RF equipment)
or marine radio when someone is within two feet of the antenna.
Repair of RITRON products should be performed only by RITRON authorized personnel.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 16 of 32
ACCESSORIES
Note: Programming kits are for use by authorized service/maintenance personnel only.
Description Item Number
Programming Kit for DTX-154/454 radios (via compatible computer) RPT-PCKT
Includes:
1) 1 software installation instructions
2) 2 programming software diskettes, 3.5” and 5.25” (1 each)
3) 1 PC/radio adapter cable (DB25F connector to 6 pin modular connector)
Factory programming of channels and features is also optional.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 17 of 32
DTX-154/454 PROGRAMMING
CHANNEL FREQUENCIES
Enter the transmit and receive frequencies for the channels (1-8) in the area indicated. The entered
frequencies must be divisible by 5 kHz or 6.25 kHz and within the unit’s operating range.
ADJUSTMENTS
Name: TX Frequency Trim
Description: Used to trim the unit on frequency during transmit.
Value Range: -31 to +32
Adjustment Range: Approximately 5 kHz total.
Default Value: 0
Comments: Sets the reference oscillator frequency during transmit. Changes made to current
channel which is highlighted. Value can be transferred to common field for all
channels or the value can be programmed on a channel by channel basis.
Name: RX Frequency Trim
Description: Used to trim the unit on frequency during receive.
Value Range: -31 to +32
Adjustment Range: Approximately 5 kHz total.
Default Value: 0
Comments: Should be set equal to TX Frequency Trim. May be fine tuned away from TX
Frequency Trim value for better distortion, but should not be necessary.
Changes made to current channel which is highlighted. Value can be transferred
to common field for all channels or the value can be programmed on a channel
by channel basis.
Name: Modulation Balance
Description: Sets the relative levels of the modulation signals going to the reference oscillator
and the VCO for transmit audio response flatness.
Value Range: -31 to +32
Default Value: 0
Comments: Changes made to current channel which is highlighted. Value can be transferred
to common field for all channels or the value can be programmed on a channel
by channel basis.
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 18 of 32
Name: TX Deviation
Description: Set maximum deviation of transmit modulation.
Value Range: 0 to +63
Default Value: 20
Comments: Changes made to current channel which is highlighted. Value can be transferred
to common field for all channels or the value can be programmed on a channel
by channel basis.
Name: AUX IN Audio Gain
Description: Sets the modulation sensitivity of the AUX IN input.
Value Range: 0 to +63
Default Value: 20
Comments: Changes made to current channel which is highlighted. Value can be transferred
to common field for all channels or the value can be programmed on a channel
by channel basis.
Name: AUX OUT Audio Gain
Description: Sets the output level of the AUX OUT signal.
Value Range: 0 to +63
Default Value: 20
Comments: Changes made to current channel which is highlighted. Value can be transferred
to common field for all channels or the value can be programmed on a channel
by channel basis.
Name: AUDIO OUT Gain
Description: Sets the output level of the AUDIO OUT signal.
Value Range: 0 to +63
Default Value: 20
Comments: Changes made to current channel which is highlighted. Value can be transferred
to common field for all channels or the value can be programmed on a channel
by channel basis.
Name: TX Output Power
Description: Sets the RF Output Power
FCC Equipment Authorization Application Exhibit. RITRON, INC. FCC ID: AIERIT11-450
Page 19 of 32
Value Range: 1 to 15
Default Value: 12
Comments: Typical values are 5 for 1 watt output, 12 for maximum rated power. Changes
made to current channel which is highlighted. Value can be transferred to
common field for all channels or the value can be programmed on a channel by
channel basis.
Name: Squelch Lower Limit
Description: Sets the RF level at which the receiver audio is muted.
Value Range: 1 to 255
Default Value: 40
Comments: Determines operation of Squelch, Busy Channel Lockout function and DCD
output. Must be set if any of these three functions are to be used. Changes made
to current channel which is highlighted. Value can be transferred to common
field for all channels or the value can be programmed on a channel by channel
basis.
Name: Squelch Upper Limit
Description: Sets the RF level at which the receiver is unmuted.
Value Range: 1 to 255
Default Value: 45
Comments: Determines operation of Squelch, Busy Channel Lockout function and DCD
output. Changes made to current channel which is highlighted. Value can be
transferred to common field for all channels or the value can be programmed on
a channel by channel basis.
Name: TX Timeout Timer
Description: Sets the maximum length of time the transmitter may be keyed continuously.
Value Range: 0 to 255
Adjustment Range: 1 to 255 seconds or disabled.
Default Value: 60
Comments: Value in seconds; zero seconds disables function. Changes made to current
channel which is highlighted. Value can be transferred to common field for all
channels or the value can be programmed on a channel by channel basis.
Name: Microphone Mute
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Description: Enables or disables the MIC IN signal.
Value Range: Off (unmuted) or On (muted).
Default Value: Off (unmuted).
Comments: Common to all channels.
Name: Clipper Filter Enable
Description: Allows bypassing the filter which follows the modulation limiter.
Value Range: Off (filter bypassed) and On (filter in circuit).
Default Value: On.
Comments: Ritron’s FCC Type Acceptance not valid unless On. Common to all channels.
Name: RX De-emphasis Enable
Description: Enables or disables de-emphasis on AUX OUT signal.
Value Range: Off (no de-emphasis) or On (de-emphasis).
Default Value: Off.
Comments: Common to all channels.
Name: Audio PA RX Enable
Description: Enables or disables the operation of the Audio PA (AUDIO OUT signal) during
receive.
Value Range: Off (no audio) or On (audio present).
Default Value: On.
Comments: Common to all channels.
Name: Audio PA TX Enable
Description: Enables or disables the operation of the Audio PA (AUDIO OUT signal) during
transmit.
Value Range: Off (no audio) or On (audio present).
Default Value: Off.
Comments: Used for transmit sidetone. Common to all channels.
Name: RX AC/DC Coupled
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Description: Sets the coupling from the discriminator to the AUX OUT audio processing
circuits on the loader board.
Value Range: AC or DC.
Default Value: AC
Comments: Sets the coupling mode into the audio circuitry; AUX OUT output coupling is
always DC coupled at 2.5 volts nominal DC value unless the parts are changed
on the Loader board. Common to all channels.
Name: TX Pre-emphasis Enable
Description: Determines whether the AUX IN signal is pre-emphasized. (MIC IN is always
pre-emphasized.)
Value Range: Off (no pre-emphasis) or On (pre-emphasis).
Default Value: Off.
Comments: Common to all channels.
Name: AUDIO OUT Squelch Enable
Description: Determines whether the AUDIO OUT signal is ever muted on the basis of
receiver signal strength.
Value Range: Off (never muted) and On (muted on the basis of signal strength).
Default Value: On.
Comments: Common to all channels.
Name: AUX OUT Squelch Enable
Description: Determines whether the AUX OUT signal is ever muted on the basis of receiver
signal strength.
Value Range: Off (never muted) and On (muted on the basis of signal strength).
Default Value: On.
Comments: Common to all channels.
Name: AUDIO OUT MON Enable
Description: Determines whether the MON input is active on the AUDIO OUT signal.
Value Range: Off (not active) or On (active).
Default Value: On.
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Comments: MON function used to override squelch operation and allow receive audio to be
present. Common to all channels.
Name: AUX OUT MON Enable
Description: Determines whether the MON input is active on the AUX OUT signal.
Value Range: Off (not active) or On (active).
Default Value: On.
Comments: MON function used to override squelch operation and allow receive audio to be
present. Common to all channels.
Name: Busy Channel Lockout Enable
Description: Determines whether the transmitter is allowed to transmit when activity is
sensed on the channel.
Value Range: Off (transmit allowed when channel busy) or On (transmit inhibited when
channel busy).
Default Value: On.
Comments: Carrier detect for this function based upon squelch setting. Common to all
channels.
Name: DCD Polarity
Description: Determines polarity of DCD output.
Value Range: Normal (Logic high when carrier present) or Inverted (Logic low when carrier
present).
Default Value: Normal.
Comments: Output is collector with internal pullup to +5 volts. Common to all channels.
Name: PTT RTS Polarity
Description: Determines polarity of PTT RTS input.
Value Range: Normal (Logic low requests transmit) or Inverted (Logic to transmit).
Default Value: Normal.
Comments: Input has internal pullup resistor to +5 volts. If Inverted value is chosen and this
input is left unconnected, the unit will go into transmit. Common to all channels.
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Name: MON Polarity
Description: Determines polarity of MON input.
Value Range: Normal (Logic low unmutes audio) and Inverted (Logic high unmutes audio).
Default Value: Normal.
Comments: Input has internal pullup resistor to +5 volts. If inverted value is chosen and this
input is left unconnected, the squelch will not function. Common to all channels.
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THEORY OF OPERATION
RF BOARD
RECEIVER
RF amplifier and bandpass filters.
The incoming RF signal from the input connector J101 passes backwards through the transmitter lowpass
filter and the electronic T/R switch to a two pole bandpass filter formed around L101 and L102. This filter
is of Cohn type with 1.5 dB insertion loss and a bandwidth of 25 MHz. This filter is followed by a low
noise amplifier stage formed around Q101. This amplifier has a gain of about 17 dB with a noise figure of
2 dB and serves to amplify the incoming RF signal above the noise of the following stages. Following this
stage is a four pole Cohn filter formed around L103 through L106. This filter has an insertion loss of 4 dB
and a bandwidth of 25 MHz. The two filter sections are narrow enough to filter out the spurious responses
of the first mixer while wide enough to support a performance bandwidth of 20 MHz.
1st mixer, 1st IF filters, and 1st IF amplifier.
IC101 is an active double balanced mixer which converts the incoming RF signal to the first intermediate
frequency (IF) of 43.65 MHz. This mixer has a gain of 0 dB and a noise figure of 10 dB. Its differential
output is matched to the first IF filter, YF101, by L107, L108, C128, and C137. An IF amplifier based
around Q102 is used to provide gain. Its output drives another IF filter section, YF102, which is identical
to YF101. These two filters serve the double function filtering out the spurious responses of the second
mixer and, with the second IF filter, of removing signals at the adjacent and further removed channels.
2nd IF IC
The output of YF102 drives the mixer internal to IC102. IC102 is an integrated FM IF IC which contains a
mixer, high gain limiting IF amplifier, FM discriminator (detector), and other support circuitry. The mixer
in IC102 converts the RF signal at the first IF to the second IF of 450 kHz. The output of the mixer exits
the IC and is filtered by the second IF filter, YF103. The output of the filter re-enters the IC and drives the
high gain limiting amplifier. Because the discriminator inside IC102 is sensitive to both amplitude and
frequency modulation components, a limiter must precede it to remove any amplitude modulation. In
addition, the noise based carrier detection system available with this product requires that the RF signal at
the discriminator stay constant in amplitude as the RF input signal level varies. The output of the limiter
amplifier drives the discriminator. The resonator for the discriminator is YF104.
Receiver audio and carrier detection
The recovered audio from pin 9 of IC102 is filtered and DC shifted by IC103A and associated components.
IC103B is a simple inverter and is used to provide inverted audio for those applications which may require
it.
Two methods of carrier detection are available on this radio. One is based upon the absolute RF signal
level at IC102’s input and the other is based upon the magnitude of the ultrasonic noise on the recovered
audio. IC102 has circuitry which develops a DC current which is proportional to the input RF signal level.
Passing this current through a resistor (R115) creates a voltage which varies from about 0.5 volts at no
signal input to about 3 volts with –70 dBm at the antenna connector. In addition, a voltage can be
developed which is proportional to the amount of noise present on the recovered audio signal. This is
effected by filtering the recovered audio such that only frequencies above the normal modulation range
remain. This prevents modulation components from being detected as noise. The filter is formed around
an op-amp internal to IC102 between pins 10 and 11 and the components connected to these two pins. The
filtered output at pin 11 is rectified by Q103B and then filtered. The output varies from about 3 volts for a
0 dB SINAD signal to about 0.5 volts for a 20 dB SINAD signal.
2nd local oscillator.
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The two mixers in this radio act to produce an output signal whose frequency is equal to the difference
between the frequency present at the RF input port and the frequency at the local oscillator port. To
convert signals at the first IF frequency of 43.65 MHz to that of the second IF at a frequency of 450 kHz, a
local oscillator signal at a frequency of 43.2 MHz (43.65 – 0.45) is used. This signal is created by tripling
the output of the radio’s 14.4 MHz master reference oscillator, Y101. Transistor Q112 acts as a frequency
tripler. Its associated components are used to bias the transistor at an harmonic rich bias point and to filter
the output such that only the third harmonic remains for use as the 2nd local oscillator.
VCO and Synthesizer
The synthesizer is responsible for generating the carrier in transmit and the first local oscillator in receive.
A voltage-controlled oscillator (VCO) is an oscillator whose frequency can be controlled by an external
signal. The synthesizer, almost wholly contained within IC108, divides the VCO frequency by digital
dividers and compares the result with an accurate reference. An error signal, proportional to the frequency
error is created which is routed to the frequency control input of the VCO. This action locks the VCO to a
frequency which is equal to the reference frequency multiplied by the divider number. To set the VCO
frequency, different divider numbers can be programmed into the synthesizer. In most synthesizer designs,
the divider must be an integer, which forces the reference frequency to be equal to the synthesizer step size.
The synthesizer IC used in this radio, however, allows the use of non-integer values for the divider which
in turn allows the reference frequency to be much higher than normal. This creates a synthesizer whose
output has lower noise, lower spurious levels, and a higher switching speed s. The reference frequency is
derived by digitally dividing the frequency of the 14.4 MHz master oscillator. When locked, the VCO
attains the same relative frequency stability as that of the master oscillator.
The VCO itself is a voltage follower Colpitts oscillator formed around Q108. One of the elements in the
resonant circuit is a varactor diode, CR106, whose capacitance when reverse biased varies as a function of
the applied voltage. Since the oscillator frequency is controlled by the resonant circuit, varying the voltage
on the varactor diode effects a change in frequency. To serve as a local oscillator for the first mixer, the
VCO operates at a frequency 43.65 MHz below that of the desired receive frequency. In transmit, the
VCO’s oscillating frequency range is shifted upward by about 44 MHz by switching C190 and L115 into
the resonant circuit. The VCO has a tuning range of about 30 MHz when its tuning voltage is varied
between 1 and 4 volts. To frequency modulate the VCO for transmit, another varactor diode, CR105, is
lightly coupled into the resonant circuit.
The output of the VCO is amplified to a level of about 0 dBm by Q107 and Q106. Q111 with R172 and
C196 act as a very low noise power supply filter for the VCO.
TRANSMITTER
PA Driver Stages
The output of the last VCO buffer drives Q105 through R151. The signal level at this point is about –10
dBm. Q105 amplifies this signal to about +5 dBm. Q104 further amplifies the signal to +17 dBm, the
level required by the PA module. The supply voltage to these two stages is switched on in transmit by
Q113.
PA Module, Lowpass filter, and T/R switch
When driven by +17 dBm, the PA module is capable of producing 5 watts or more of power at the antenna
connector. Pin 2 of the module is used for power control. The output power level can be varied from less
than 0.5 watts to full power by changing the voltage at this pin.
To reduce carrier frequency harmonics of the PA module output to acceptable levels, a lowpass filter is
inserted between the module and the antenna connector. This filter is of elliptic design and formed around
a buried stripline transmission line and C164, C165, and C166.
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To isolate the PA module from the receiver, an electronic T/R switch is used. The switch is formed around
PIN diodes CR101 and CR104 which are turned on in transmit and are off in receive. CR104 switches the
PA module into and out of the circuit while CR101 protects and isolates the receiver input when the radio is
in transmit.
MISCELLANEOUS FUNCTIONS
Two on-board regulators are used to provide the 5 volts DC used by most of the circuitry in the radio.
IC106 is a low noise, low dropout regulator which provides 5 volts to all the portions of the radio which do
not get switched on or off as the radio changes from transmit to receive. This regulator is enabled by the
XCVR-EN (J102, pin 5) input. When this regulator is not enabled, the radio is essentially powered down.
IC107 is an identical regulator which supplies power to those circuits which are to be powered-up only in
receive and to the switches in the VCO which shift the VCO frequency range to that needed as the 1st local
oscillator. The regulator is enabled through IC105E and IC105F by the RX-EN (J102, pin 4) input.
The transmitter PA module driver stages and the T/R switch are powered by +7.2 volts through Q113.
Q113 is enabled by the TX-EN (J102, pin3) input through delay and sequencing circuitry formed around
IC105 and Q115 and Q114. The sequencing circuitry delays PA turn-on until the driver stages and T/R
switches are on and delays driver stage and T/R switch shutdown until the PA module has ramped down in
power. This prevents “keyclicks” from abrupt transmitter turn-on and turn-off.
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THEORY OF OPERATION
LOADER BOARD
The loader board is responsible for controlling the operation of the RF board and for processing the audio
input and output signals to and from the RF board.
Transmit Audio Chain
Two audio inputs are available to the user. One, MIC IN is, as its name implies, is designed to accept a
microphone-like input for modulation of the transmitter. The other, AUX IN, is designed to be more
flexible in terms of gain and pre-emphasis.
The signal at the MIC IN input is applied to pin 3 of IC308A after passing through a blocking capacitor,
C342. R378 is used as a bias source for those microphone which may require it e.g. electret, carbon, etc.
IC308A is configured as a unity gain buffer amplifier. Its output is fed through the pre-emphasis network
formed by C344 and R337 to IC308B. IC308B is an amplifier used to boost the level of the input signal.
The output at pin 7 is fed to an analog switch, IC309C. This switch is used to mute the signal in those
cases when the MIC IN input is not used. The output of the switch is routed to the input of the clipper
IC310A.
Signals at the AUX IN input are routed to IC308D. Provisions exist to either allow this input to be DC
coupled or AC coupled by installing R354 or R355. IC308D is a unity gain buffer amplifier. Its output is
fed to analog switch IC309B. This switch allows C361 to be inserted into the path from IC308D to IC308C
to work with R358 as a pre-emphasis network. IC308C is a unity gain inverting amplifier. Its purpose is to
insure that there is an even number of inversions between the AUX IN input and the modulation input on
the RF board. The output at pin 8 drives the AUX TX GAIN section of digital potentiometer IC307A.
The signal at the wiper of the digital potentiometer is routed to the input of the clipper, IC310A.
The clipper limits the amplitude of all signals at its input by virtue of the fact that the signal at its output
can not swing above the positive supply voltage or below ground. To prevent clipping in the following
stages, the signal level at the clipper output is reduced by R344 and R345. Following the clipper is an
analog switch, IC303 which is used as a mute gate. The output of the mute gate drives a fifth order pseudo-
raised cosine lowpass filter formed around IC310B and IC310C which removes harmonics created in the
clipping process. For those systems where the AUX IN signal is already limited in amplitude and
frequency, the clipper filter can be bypassed by enabling IC303C. The clipped and filtered signal at pin 8
of IC310C is fed through the DEVIATION section of the digital potentiometer, IC307B. The signal is then
routed to IC310D where it is summed with a DC voltage from the TX FREQ section of the digital
potentiometer and also inverted. The output at pin 14 is fed to the modulation input of the RF board.
To produce the signal for the VCO modulation input on the RF board, the output at pin 14 of IC310D is
also fed through the BALANCE section of the digital potentiometer, through a blocking capacitor and to
the VCO modulation input of the RF board. This allows the reference oscillator and the VCO on the RF
board to be fed with modulation signals whose amplitude can be independently controlled. This is
necessary to achieve a flat transmit audio frequency response on the RF board.
Receive Audio Chain
Two receive audio paths are available to the user. One is similar to that found on voice two-way radios in
that it can drive a low impedance speaker. The other has an output which is designed for line level at 600
ohms.
Discriminator audio from the RF board is passed to analog switch IC305C which determines whether the
signal is to be AC or DC coupled to the buffer amplifier IC306A. The output at pin 1 drives the two
receive audio paths. For the path which can drive a speaker, the output of IC306A is passed through a de-
emphasis network R330/C340 and then to a buffer amplifier IC306B. The output of IC306B is routed
through R332 and C341 to the RX AUDIO GAIN section of the digital potentiometer. The output of the
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digital potentiometer feeds the input to the audio power amplifier, IC301. The output of the audio power
amplifier at pin 5 passes through blocking capacitor C318 and on to pin 12 of J301. The audio power
amplifier is enabled and disabled by controlling its power supply voltage through Q310 and Q302.
Transmit audio sidetone is provided by passing the transmit audio signal through R309 to the audio power
amplifier.
The other receive audio path passes from pin 1 of IC306A through two analog switch sections is tandem.
The first, IC305A switches in or out a de-emphasis network formed with R330 and C340. The second
section, IC305B is used as a mute gate. The output of the mute gate passes through a unity gain buffer,
IC306C and to the AUX RX GAIN section of the digital potentiometer. From the digital potentiometer, the
signal passes through a gain of 4.3 amplifier, IC306D and on to pin 8 of J301.
MISCELLANEOUS FUNCTIONS
The microcontroller, IC302, controls the operation of the loader board as well as communicating with the
user interface software and the RF board. Because the processor IC itself doesn’t have enough I/O to
support all of the functions required, two shift registers, IC312 and IC313 are used as output port
expanders. IC311 is used to store frequencies and operating parameters such as the settings of the digital
potentiometer. This memory device is non-volatile, meaning that the memory contents are not lost when
power is removed from the device.
The RSSI signal from the RF board used for carrier detection is amplified by IC304C and then applied to
one of the analog to digital converter inputs of the microcontroller. The PWR SET voltage for setting the
RF power output level on the RF board is developed by digital to analog converter using four output pins of
the microcontroller and a weighted resistor network, R316 through R321 and IC304D. Because one of the
pins is shared with the carrier detect function, analog switch IC303B is used to switch the pin to the
appropriate circuitry.
Except for the audio PA IC, IC301, all of the active devices are powered from 5 volts. Two regulators are
used to provide this voltage. One, IC314, is a low noise, high stability device which is used to power the
audio stages of the board. Its high stability is required because the loader board develops the DC bias for
the reference oscillator on the RF board. Any drift in DC voltage causes a corresponding drift in operating
frequency. The other regulator, IC315, is used to power the digital devices. Low noise, stable bias for the
operational amplifiers is generated by R361, R362, IC304A, and IC304B.
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ALIGNMENT INSTRUCTIONS
ALL ADJUSTMENTS REQUIRED FOR ALIGNMENT ARE EFFECTED ELECTRONICALLY
THROUGH COMPUTER INTERFACE USING RPT-PCPK SOFTWARE. THE DTX-154/454 COVER
DOES NOT HAVE TO BE REMOVED FROM THE UNIT FOR ALIGNMENT.
RECOMMENDED EQUIPMENT
1. Power Supply-0 to 15 volts, 3 ampere current capability.
2. FM Service Monitor (500 MHz RF capability).
3. Oscilloscope (100 kHz min.)
4. FM Deviation Meter.
5. RF Wattmeter, 10 watts full scale.
6. Frequency Counter (500 MHz min.)
7. SINAD measuring device.
8. VTVM or DMM.
9. 30 dB RF Power Attenuator.
10. Audio Generator, 300 to 300 Hz, 0 to 1V RMS output.
11. RITRON model RTX-SRVBD adapter
12. RSM-3X
13. PC computer and RITRON PC programmer kit.
Note: The FM Service Monitor may contain include many of the other instruments required.
RADIO PREPARATION
Connect the programming adapter to pin 9 of the radio’s DB-15 connector. Install the programming
software and open the program. Select the DTX-154/454 radio from the radio menu. If the unit has never
been programmed before, the settings should be at their default settings as shipped. If any changes have
been made, however, for alignment, the settings should be placed at the default value as shown below:
Function Value
TX Frequency Trim 0
RX Frequency Trim 0
Modulation Balance 0
TX Deviation `20
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AUX IN Audio Gain 20
AUX OUT Audio Gain 20
AUDIO OUT Gain 20
TX Output Power 12
Squelch Lower Limit 40
Squelch Upper Limit 45
TX Timeout Timer 60
Clipper Filter Enable On
RX De-emphasis Enable Off
Audio PA RX Enable On
RX AC/DC Coupled AC
TX Pre-emphasis Enable Off
AUDIO OUT Squelch Enable On
AUX OUT Squelch Enable On
AUDIO MON Enable On
AUX OUT MON Enable On
Busy Channel Lockout Enable On
DCD Polarity Normal
PTT RTS Polarity Normal
MON Polarity Normal
SETUP
Using the VTVM (or DMM), set the Power Supply to the correct supply voltage. Connect the positive lead
of the supply to pin 6 of the radio’s DB-15 connector. Connect the negative lead to pin 15. Connect the
FM Service Monitor to the BNC RF connector on the unit.
Program the desired operating frequencies into the unit for both transmit and receive.
TRANSMITTER
Output Power
In the programming program, advance to the TX Output Power section. The current channel will be
highlighted. Key the unit via the program and adjust the TX POWER value until the correct power is
noted. Repeat for all channels. The unit must be un-keyed before a channel can be changed.
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Frequency
Note: The unit must be at an ambient temperature of 22 +/- 1 C (71.6 +/- 1.8 F) for proper setting of
frequency.
Move to the TX Frequency Trim section of the programming software. Choose a channel whose frequency
is near the middle of the group of programmed channels. Set the Service Monitor to display transmit
frequency or connect a Frequency Counter to the unit through a Power Attenuator. Key the unit via the
program and adjust the value for the correct frequency. If the unit has been programmed correctly, this
value should be satisfactory for all channels and can be made common to all channels in the program. If
desired, however, the frequency for each channel may be set individually.
Deviation and Balance
An audio generator set to 500 Hz should be connected to pin 7 (AUX IN) of the DB-15 connector. The
output level should be set for 500 mv RMS. The RF output of the unit should be connected to the FM
Service Monitor. The Service should be set up to display the demodulated output signal on an oscilloscope.
Minimal filtering of the demodulated signal, especially on the low frequency end, should be used. De-
emphasis should not be used.
Move to the Modulation Balance section of the program. Select a channel near the middle of the
programmed frequency range. Key the unit and confirm that a sinewave or clipped sinewave is visible on
the oscilloscope. Increase the audio generator level until clipping is clearly visible. Adjust the value until
the clipped portion is as flat as possible. There may be some initial overshoot at the clipping point, but the
region after should be flat. This adjustment must be repeated for all channels if the frequencies differ by 2
MHz or more.
Move to the TX Deviation section of the program. Set the FM Service Monitor to measure transmitter
modulation deviation or connect an FM Deviation meter to the unit through the RF Power Attenuator.
With the audio generator still connected and set at the same level as above, adjust the frequency of the
generator until the greatest deviation is noted. Set the deviation value to product the correct maximum
deviation, i.e. 2.5 kHz for 12.5 kHz operation and 5 kHz for 25 kHz operation. This adjustment must be
repeated for all channels if the frequencies differ by 2 MHz or more.
Other Functions
The other features/functions of the unit should be set via the programming software for transmit operation
as desired or returned to the previous settings.
RECEIVER
The AUDIO OUT pin (pin 12 on the DB-15 connector) on the unit should be connected an oscilloscope.
Connect the RX MON pin (pin 11 on the DB-15 connector) to ground. Noise should be visible on the
oscilloscope.
Front-End
The front-end filters have been tuned at the factory for optimum performance across the entire frequency
band of operation. Unless the factory settings have been altered, no adjustment is necessary or advisable.
Aligning the front-end requires programming the unit for receive frequencies at the center and each end of
the band and noting the sensitivity at these three frequencies. With a SINAD meter attached to the AUDIO
OUT pin, the sensitivity should be at or below specification at all receive frequencies. If it is not, the slugs
in L101 through L106 should be made flush with the top of their cans and then turned clockwise 1 turn so
that the slug is slightly recessed into the can.
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The sensitivity should be checked and compared at the center and band edges. If the sensitivity is
significantly worse (3 dB or more change required at the RF generator), at one frequency, each slug should
be varied in position slightly and the one(s) having the most effect should be adjusted slightly for improved
sensitivity. The other channels should be checked to insure that sensitivity has not degraded. This process
may need to be repeated a number of times at different channels to insure satisfactory sensitivity across the
band. Typically, the sensitivity is slightly better (about 1 dB on the RF generator) at the center channel.
Frequency
Because the transmitter and receiver use the same reference oscillator, TX Frequency Trim values can be
used for receive also. If a common value was used for transmit, this value is also already stored as the
correct value for receive. If different values are used per channel on transmit, the default value or possibly,
the average of the values used in transmit, should be used. For some critical applications it may be possible
to optimize the receive frequency trim values by connecting a distortion meter (a SINAD meter may be
used if the 1 kHz tone on the generator is adjusted in frequency for highest SINAD) to the AUX OUT pin
and adjusting for lowest distortion on a noise quieted RF signal at the correct frequency.
Squelch Setting
The squelch is set by moving to the Squelch Lower Limit section of the program and setting the RF
generator output level to the point below which the receiver will be muted (squelched). This point may be
determined either by a SINAD reading or by RF level. The choice should be determined by how resistors
R124 and R125 are set (the default setting is for SINAD based squelch). When the proper level is reached,
the proper command is set in the program and the RSSI value from the RF board at that instant is stored as
the lower limit squelch setting.
The upper squelch limit is set by moving to the Squelch Upper Limit section of the program. The RF
generator level should be set to the point above which the receiver will always be unmuted. Typically, this
setting is a few dB’s higher in RF level that the lower squelch limit. The difference between the two values
is the squelch hysteresis and prevents squelch chattering.
Other Functions
The other features/functions of the unit should be set via the programming software for receive operation as
desired or returned to the previous settings.