PRC1099A-MS
2-1
Chapter 2: System Overview
This chapter provides an overview of the various PRC1099A’s operations
including frequency conversion, receive and transmit paths and control signals.
Chapter 3 through 14 provides detailed circuit descriptions of each board as
well as technical specifications and servicing data. Figure 2-2 on page 2-14
provides a system block diagram and Figure 2-3 on page 2-15 provides a wiring
diagram.
2.1
Frequency Conversion
The PRC1099A up-converts transmit signals from 1650 or 1647 kHz to
75 MHz IF and then down-coverts the 75 MHz IF to the selected channel
frequency (1.6 to 30 MHz). The receive signal is first up-converted from the
selected channel frequency to the 75 MHz IF and then down-converted to either
1650 or 1647 kHz IF modulated by the receive audio.
In transmit mode, the PRC1099A mixes the modulated 1650 or 1647 kHz IF
with the 73.35 MHz second LO to the first IF output at 75 MHz, the Direct
Digital Synthesizer (DDS) generates the first local oscillator (LO) frequency in
the range of 76.6 and 105 MHz in 1 Hz steps. The second conversion from
75 MHz to 1650 kHz requires a local oscillator frequency of 73.35 MHz.
The PRC1099A provides selectable USB/LSB operation using separate BFO
frequencies of 1650 and 1647 kHz, respectively. The synthesizer is
automatically offset by 3 kHz when the sidebands are switched however, there
is no change in the output frequency.
