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SM-2150/VHF ALIGNMENT PROCEDURE
It is important that the TCXO be on the correct frequency before performing a complete alignment of the
radio. An incorrect TCXO frequency can impair the performance and even cause mis-alignments.
Normally the transmitter is monitored with a frequency counter or service monitor while the transmitter is
keyed at it’s highest frequency. The TCXO is adjusted for the least frequency error. Typically the
frequency is 470MHz with a frequency error of +/-750Hz or less. TC701 adjusts the center frequency if
necessary.
PLL Alignment
•
NOTE: If the PLL is out- of- lock, an audible warning will be heard and the front panel red
LED will flash.
1. Connect an RF power meter to the ANT socket.
2. Using the channel switch, select channel with the lowest transmit frequency.
3. Connect a DC voltmeter to test point 1 (TP1) accessed via the hole in the VCO cover.
4. Set the PTT switch to transmit.
•
Note:The transmitter switching band width of this radio is 25MHz. A transmitter frequency
range of more than 26MHz may be programmed and used if the voltage specification in step 5 is
met.
5. Adjusting L353, set the voltage measured at TP1, measure and check that the voltage is above 2.1
volts. If the voltage is below 2.1 volts the transmitter frequency programmed is too high for the
operating bandwidth of the radio.
6. Set the PTT switch to receive.
7. Using the channel switch select channel with the lowest receive frequency.
8. Adjusting L356, set the voltage measured at TP1. Measure and check that the voltage is above 1.5
volts. If the voltage is below 1.5 volts the receive frequency programmed is too high for the
operating bandwidth of the radio.
•
Note:The receiver switching bandwidth of this radio is 26MHz. A receiver frequency range of
more than 26MHz may be programmed and used if the voltage specification in Step 8 is met.
There may be some degradation in actual receiver performance, if bandwidth of more than
26MHz is used.
MAXON SM-2000 MOBILE
SM-2150/VHF ALIGNMENT PROCEDURE
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December 98