Transmitter Mode Selection - SEA 222 Operator's Manual

6. MODE AND FREQUENCY CONTROL
6.1 GENERAL
6.1.1
In the SEA 222, the frequency of ope rat j on is determi 11ed by 1 oad i ng
a serial bit stream containing a binary number in the
tw~
synthesizer
chip registers in the frequency synthesizer circuitry.
These binary numbers are calculated through an internal algorithm
by the control computer. When the computer loads a desired frequency
into the control computer, the computer tben calculates all the re-
quired binary data streams and inputs the information into the vari.ous
control registers.
Such data as filter band, VCO band {high or low), VCO loop divide-
by-N, VCXO loop divide-by-N and various control bits are all calculated
by the computer, once the desired channel is entered by the operator.
TRANSMITTER MODE SELECTION
The primary mode of operation of the SEA 222 is in the A3J {SSB with
fully suppressed carrier) mode.
Two auxiliary modes are provided:
A3A: SSB with. pilot carrier re-inserted16 dB below PEP.
A3H: SSB with pilot carrier re-inserted 6 dB below PEP {AM equiva-
1 ent).
A3J is the basic SSB operating mode and is used for ship to ship,
base station to ship and point to point communications.
A3H is a secondary mode, designed to allow a degree of compatability
between old style AM equipment and SSB systems. In this mode, the
carrier is suppressed only 3 to 6 dB below PEP. Such systems are
inherently wasteful of the power capability of any SSB transmitter. As
required by law, the "E #0
11
channel is provided with A3H carrier. (See
Page 2 -Operating Modes.)
In the SEA 222, the normal mode of operation is ALWAYS A3J. On
public correspondence channels, the operator may, if desired, insert a
-16 dB carrier, by entering the desired A3A 'channel into
11
scratchpad
11
memory and inserting the A3A bit (See
~
3.3.2 for scratchpad pro-
gramming information.)
A3H mode operation on 2182.0 KHz (the international distress and calling
frequency) is available by recalling emergency channel E#O.
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