Sailor RE2100, Техническое руководство

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3 SERVICE RE2100
6.
3.6.1.2 CHECK OF LO2 AND REINJECTION SIGNALS
The LO2 signal is used in the mixing process from the 1st IF at 70.00064 MHz to the 2nd IF at 10.73152
MHz. The frequency of the LO2 signal is 59.26912 MHz when receiving a H3E signal or J3E-USB signal.
In J3E-LSB mode the frequency of the LO2 signal is 80.73216 MHz.
The carrier reinjection signal is used in the detection of signals with a reduced carrier or signals without
any carrier. The frequency of the carrier reinjection signal is 10.73152 MHz and is given by the TCXO.
1. Turn the RE2100 on and select J3E-USB mode.
2. To check the LO2 signal, connect the diode probe across the resistor R188-1, which is located at
the output of the LO buffer at the Receiver Unit (module 1).
3. Check the measured DC voltage to be 3.3V +/-0.5V.
4. To check the reinjection signal connect a DC voltmeter through the diode probe to pin 8 at the
detector IC (LM3189).
5. Check the measured DC voltage to be 300 mV +/-50 mV.
3.6.1.3 CHECK OF CRYSTAL FILTERS (2nd IF)
The selectivity of the second intermediate frequency is given by the crystal filters (SSB or AM filter), which
form an important part of the overall receiver selectivity.
If the 2nd IF selectivity cannot fulfil the specified requirements, it is probably caused by a mistuning of the
two crystal filters or by a mistuning of the 1st IF filter at 70 MHz.
The crystal filters are tuned by the trimming capacitor C18-1, which is located at the receiver unit. The
adjustment procedure for this capacitor is described in section 3.7.1.3.
The 1st IF filter is tuned by three trimming coils and two transformers. The adjustment procedure for these
components is described in section 3.7.1.1.
In this test of selectivity, the 6 dB bandwidth and the stop band attenuation is controlled. The test is
performed by using variations in the level detector output voltage, which can be measured at testpoint
TP1-1 in the AGC circuit. The voltage can be measured by using an analog multimeter, but it is easier
to use a digital multimeter, because the variations in the level detector output voltage are relatively small
(about 200 mV).
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