GENERAL OPERATIONS
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GENERAL INFORMATION
CAUTION
!
Do not attempt to transmit until the radiotelephone has warmed up for at least 3
minutes. Transmitting before the 3 minute warm up period can cause a violation
of the Federal Communications Commission regulations.
PROPAGATION
Medium Frequencies (MF) in the range of 300 KHz to 3 MHz propagate far
beyond the horizon. MF frequencies are generally usable within 300 miles
depending on the time of day, atmospheric conditions and man-made noise
levels.
High Frequencies (HF) in the range of 3 MHz to 30 MHz allow communications
over thousands of miles, again subject to the time of day and atmospheric
conditions. Interference tends to be more of a problem than on Very High
Frequencies (VHF) in the range of 30 MHz to 300 MHz.
To further understand MF/HF propagation, SEA’s “Mariners Guide to Single
Sideband” (MAN-0001-001) is highly recommended reading.
INSTALLATION (RF grounding & DC connections)
A radio frequency (RF) ground with a minimum of 100 sq. ft. is required for
proper operation. This ground system is not unique to SEA equipment. All
marine MF/HF radios have the same installation requirements for maximum
efficiency. Every connection to the ground should be made with a minimum of
2” wide copper strap. Proper wire size must be used between the radio and
power supply to prevent the DC (direct current) voltage at the radio from
dropping below 11.5 volts during transmit conditions. Should this occur, the
radio will drop to low power during transmit to prevent distorted transmissions.
It is recommended that an authorized SEA dealer perform the installation of your
MF/HF equipment to assure proper operation. For complete installation
instructions, refer to the “SEA 235 Installation Manual” (OPR-235-INST)
supplied with the radio.
RADIO PROTECTION
The SEA 235 monitors radio conditions such as DC supply voltage, internal
temperature and antenna VSWR. When these conditions are outside the preset
limits, the radio will revert to low power (approximately 75 Watts). The
display’s LOW indicator will light to indicate this condition. If this should occur
during an EMERGENCY situation, pressing will
override the monitoring sensors and allow FULL output power. The radio will
stay in the EMERGENCY OVERRIDE condition until the radio power is re-
cycled.
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FNC
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