User's Manual

MAXON SD-125 RF LINK MODULE
The SD125E Series radio requires the ACC-900E Programming Software, 9-15 VDC 200mA Power Supply
and ACC2125 Programmer Interface Cable. Refer to the ACC-900E Programming for detailed information on
programming the SD125E Series radio.
The SD-125 UHF/VHF Receiver is by design, broad band covering UHF(400-430 MHz & 440-470 MHz &
470-490MHz) and VHF(148-174 MHz) and should require no special alignment, unless repairs are performed
on the receiver portion.
Should repairs be necessary, use the "Test Equipment Diagram" on page 17 & the "Alignment Points
Diagram" on page 18, in conjunction with the following procedures:
• An Extender Board is required in order to separate the Digital and RF PCB’s to allow access to the
alignment points. Installation instructions are provided with the Extender Board Assembly.
RECEIVER
1 Apply a standard test signal to the receiver antenna terminals.
2 Adjust T1 for maximum sensitivity and audio output with minimum audio distortion.
3 Adjust RV403 for the specific audio output level.
RX VCO
1 Set the unit to the highest receive frequency, 470MHz(UHF), 174MHz(VHF) and adjust the VCO L303
to 8 volts.
2 Set the unit to the lowest receive frequency 440MHz(UHF), 148(VHF) and check that the VCO voltage
is above 2.0 volts. If voltage is below 2.0 volts, adjust L303 for 2.0 volts or more.
• Note: Use TP1 to measure the voltage.
TRANSMITTER
Connect the unit to a Service Monitor with the power meter setting to the 10 W scale (or autorange)
TCXO
Set the channel selector to the mid-range frequency 460 MHz, adjust TCX01 for a reading of 460 MHz
±200Hz (155 MHz VHF models).
TX VCO
1 Set the unit to the highest transmit frequency, 470MHz(UHF), 174MHz(VHF) key the transmitter and
adjust the VCO L203 to 8 volts.
2 Set the unit to the lowest transmit frequency 440 MHz(UHF), 148(VHF) key the transmitter and check
that the VCO voltage is above 2.0 volts. If voltage is below 2.0 volts, adjust L203 for 2.0 volts or more.
• Note: use TP1 to measure the voltage.