BendixKing PS440 System KHF 1050 - Manual (Page 26)

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Revision 1 May/2003 KHF 1050/PS440 Pilot’s Guide
NOTE: Lower sideband isn’t normally used in the aviation services.
During installation of the KHF 1050 system, LSB may be enabled for use
in regions or applications where its use authorized.
The result is that an SSB system has the effective transmit power of AM
units having many more times the transmitter power. Also, SSB commu-
nications allow the frequency band to be utilized more efficiently since
the space or “bandwidth” of only one sideband rather than two sidebands
is required to transmit the message.
SUPPRESSED CARRIER VS. REDUCED CARRIER
The single sideband (SSB) operation just described with the carrier fre-
quency virtually eliminated is actually referred to as single sideband sup-
pressed carrier. If just a small portion of the carrier is transmitted along
with the sideband, the operation is referred to as single sideband
reduced carrier.
SIMPLEX AND SEMI-DUPLEX OPERATION
The KHF 1050 is capable of both simplex and semi-duplex operation.
Simplex operation means that communication signals are transmitted
and received on the same frequency. Simplex operations are used
when communicating with Air Traffic Control (ATC), for example. Semi-
duplex operation means that messages are transmitted on one frequen-
cy and received on another. The HF operator selects separate transmit
and receive frequencies, then keys the microphone to transmit and
releases the push-to-talk switch to receive. Semi-duplex operation is
usually used for maritime radiotelephone (public correspondence) com-
munications.
SINGLE SIDEBAND (SSB)
fc = carrier frequency
fm = modulating frequency (voice)
fc-fm
LSB
fc fc+fm
USB
Figure 3A - Single Sideband
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