User's Manual

MaxonSM5102Radio
Receiver Audio and Sub-audio Circuit
The receiver audio circuit has been fully controlled by Baseband Process, CMX881 supported by CML using
internal software program.
Frequency and CTCSS/DCS data storage
EEPROM
Rx/Tx channels, CTCSS/DCS as well as other data from the programmer are stored in the EEPROM.
The data stored is retained without power supplied. This is a non-volatile memory. The EEPROM
may have information re-programmed or erased. U6 is an EEPROM with 32Kbite capacity and data is
written and read serially
Mute (squelch) Circuit
The mute circuit switches off the power amplifier when no audio signal is present. The squelch circuit consists of U2
and RV2,RV3 and their associated components. The noise signal form pin 9 of U2 is amplified by internal amp of
U2and then fed into RV2, RV3. RV2,RV3 is used to adjust the squelch circuit sensitivity and is normally adjusted to
produce noise squelch opening sensitivity of 10dB to 12dB SINAD
Speaker Audio Amplifier
After signal detection and audio filtering , Via U14on the RF board, the low level audio is returned to the digital board.
This is then routed to Pin22 of U13 to provide speaker audio.
MAINTENANCE AND REPAIR
GENERAL
VHF
The VHF hand portable radio covers the VHF band from 146 to 174MHz. The radio have been factory aligned for
operation within frequency band.
Any repair or adjustment should only be made by or under the supervision of a qualified radio service technician.
ALIGNMENT PROCEDURE
The PM-200 V2 Receiver is designed for broad band covering VHF(146-174MHz) and should require no special
alignment, unless repairs are performed on the receiver portion.
The only alignment normally required is to squelch circuit, Apply a signal that produes 10dB SINAD, reduce the input
to -130dBm, close the squelch control(RV2,RV3,) until the receiver mutes.
Increase the signal to 10dB SINAD reading reference level and adjust RV2 or RV3 until the squelch opens. In high
noise environment, some users may prefer to have the squelch opening set somewhat tighter, e.g.:12 to 14dB SINAD.
Should repairs be required, the following procedures should be applied:
VCO
1. Set the unit to the lowest transmitter frequency, 146MHz(VHF), and adjust the VCO L203 to 2.5V and 1.0V
respectively.
2. Set the unit to the highest transmitter frequency, 174MHz(VHF), and check that the VCO voltage is below 14 volts.
3. Set the unit to the lowest receiver frequency, 146MHz(VHF), and adjust the VCO 302 to 1.5V.
4. Set the unit to the highest receiver frequency 174MHz(VHF),) and check that the VCO voltage is below 14 volts.
* Note : use L203,L303 to measure the voltage.
Transmitter
Connect the unit to a Service Monitor with the power meter setting to the 46 W scale (or autorange)