DE
DANIELS
ELECTRONICS
Enhanced AM/FM Synthesizer Instruction Manual OS(R/T)-3(A/H) 29 - 470 MHz
3-5
3 . 5 . 5 . 2
VHF OS(R/T)-3A 118 - 159.4 MHz Alignment
Refer to the "OS(R/T)-3A 118 - 159.4 MHz Analog Board Component Layout" diagrams and the
"OS(R/T)-3A 118 - 159.4 MHz Analog Board Schematic Diagram" located in section 4 on pages
5, 6, and 7.
Using a high impedance (10 M
Ω
) DC Voltmeter, measure the PLL control voltage at TP4 located
on the synthesizer module analog board (top). Access to TP4 is available through the synthesizer
top cover. The VHF synthesizers operating in the 118 - 159.4 MHz frequency range employ a PIC
microcontroller having no frequency adjustment capability. The OST-3A128 and OSR-3A149
models cover 118-138 MHz, and 139.4 - 159.4 MHz respectively and provide full band coverage
without tuning adjustment.
All channel selections might result in a TP4 voltage within the +3.1 to +3.5 Vdc range. Channel
selections beyond the tuning range capability of the synthesizer will result in unlocked operation
over the temperature range - 40C to + 60C. The tuning range capability of all synthesizer models is
listed in the Specifications section of this manual.
3 . 5 . 5 . 3
VHF OS(R/T)-3H 128 - 174 MHz VCO Alignment
Refer to the "OS(R/T)-3H 128 - 174 MHz Analog Board Component Layout" diagrams and the
"OS(R/T)-3H 128 - 174 MHz Analog Board Schematic Diagram" located in section 4 on pages 9,
10 and 11.
Using a high impedance (10 M
Ω
) DC Voltmeter, measure the PLL control voltage at TP4 located
on the synthesizer module analog board (top). Access to TP4 is available through the synthesizer
top cover. Using a small standard blade screwdriver, carefully adjust the VCO fine frequency
"TUNE" trimmer capacitor C24 until a test point (TP4) voltage of approxi2.3 Vdc is
obtained. Measured PLL loop control voltages below approxi0.5 Vdc and above
approxi4.5 Vdc indicates an "out of lock" synthesizer condition.
It is important to check the loop control voltage at TP4 when multiple synthesizer channels have
been programmed. All channel selections should result in a TP4 voltage within the +1.0 to +4.0
Vdc range. Adjust the fine tuning capacitor C24 to center multiple channel voltages symmetrically
about +2.3 Vdc. Channel selections beyond the tuning range capability of the synthesizer will
result in unlocked operation. The tuning range capability of all synthesizer models is listed in the
Specifications section of this manual.
