Principle Of Operation - Sailor RE2100 Technical Manual

1 GENERAL INFORMATION RE2100

1.6 PRINCIPLE OF OPERATION

SAILOR Compact HF SSB RE2100 is the control unit in SAILOR Compact HF SSB Programme 2000. It
contains following circuits.
PROCESSOR UNIT
This unit controls all modules and operate as interface between the user and the radio (keyboard, display).
Nearly all communication from the microprocessor to the modules is done on an internal serial bus (SPI).
The unit holds all memory, and all user defined memory is in an EEPROM, so even when supply voltage
is removed, the contents of the memory is preserved. If the supply voltage to the RE2100 gets too low,
the display will show error 20, and the performance of the RE2100 will be reduced.
There is also an external serial bus (SP-Bus). This bus is used to communicate with other units in the
SAILOR Compact HF SSB Programme 2000, e.g. the transmitter T2130.
The microprocessor also generates the alarm tones (1300 Hz, 2100 Hz).
DISPLAY UNIT
This unit contains the display and the field strength meter.
SYNTHESIZER UNIT
This unit contains all frequency generating parts.
There is only one reference oscillator which is a temperature compensated crystal oscillator (TCXO) with
a frequency of 10.73 MHz.
Both receiver and exciter are using two LO-signals. These signals are generated in two separate PLL's,
one having output frequencies from 70 MHz to 100 MHz and the other having output frequencies of 59.27
MHz and 80.73 MHz.
The synthesizer which covers from 70 to 100 MHz is a fractional synthesizer with a resolution of 10 Hz.
The other synthesizer is a conventional synthesizer. It has two output frequencies, one for lower sideband
80.73 MHz and another for upper sideband 59.27 MHz.
RECEIVER FRONT END
This unit contains input protection circuit, input filters, mixer and 70 MHz IF.
The input filter is a mixture of lowpass, highpass and bandpass filter to obtain max. performance in the
entire band from 100 kHz to 30 MHz.
The mixer is a FET mixer with a high level LO-injection to give the mixer good high signal quality. The mixer
is followed by a 70 MHz bilitic quartz filter with a bandwidth of 15 kHz.
RECEIVER UNIT
This unit contains all necessary circuits to convert a 70 MHz IF signal to an audio signal.
It starts with the second mixer which is a FET mixer. From the mixer the signal is fed to a high order
monolitic quartz filter, one for AM and one for SSB. The type of filter is selected from the microprocessor.
From the filter the signal is fed to the 10.73 MHz IF amplifier. The gain of this amplifier is regulated from
the AGC amplifier. The regulated IF amplifier is followed by a ceramic filter to reduce the wideband noise.
The signal is from here fed to the demodulator, which can operate as an SSB detector or an AM detector
controlled from the microprocessor. The detector is followed by a filter circuit. In AM mode the filter width
is from 70 Hz to 3000 Hz, and in SSB mode the filter is from 300 Hz to 3000 Hz. From here the AF signal
passes some switches and then it is amplified in three AF amplifiers, one for the microtelephone earpiece,
one for the 0 dBm output, and an amplifier with volume control for the AF signal to the AF power amplifier
in T2130.
The signal from the AF filters is also fed to the voice controlled squelch. This contains a limiting amplifier,
a frequency to voltage converter, and a threshold amplifier. On/off switching of the squelch is controlled
by the microprocessor.
In scan mode the squelch is used to detect if there is signal on the channel in question.
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