Galaxy DX 88HL Panduan Pemilik - Halaman 8

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RECEIVING SSB SIGNALS

There are four types of signals presently used for communications: FM,

AM, USB and LSB. When the MODE switch on your unit is placed in the

AM position, only standard double-sideband and in FM position, only

frequency deviation, full carrier signals will be detected. An SSB signal may

be recognized while in the AM or FM mode by its characteristic "Donald

Duck" sound and the inability of the AM or FM detector to procedure an

intelligible output. The USB and LSB modes will detect upper sideband and

lower sideband respectively and standard AM signals.

SSB reception differs from standard AM reception in that SSB receiver

does not require a carrier or opposite sideband to produce an intelligible

signal. A single-sideband transmitted signal consists only of the upper or

lower sideband and no carrier is transmitted. The elimination of the carrier

from the AM signal helps to eliminate the biggest cause of whistles and tones

heard on channels that make even moderately strong AM signals unreadable.

Also, SSB takes only half of an AM channel, therefore two SSB

conversations will fit into each channel, expanding the 40 AM channels to 80

SSB channels. The reduction in channel space required also helps in the

receiver because only half of the noise and interference can be received with

100% of the SSB signal.

An SSB signal may be received only when the listening receiver is

functioning in the same mode. In other words, an upper sideband signals

(USB) may be made intelligible only if the receive is functioning in the USB

position.

If a lower sideband (LSB) signal is heard when the receiver is in the

USB mode, no amount of tuning will make the signal intelligible. The reason

for this may be understood if you consider that when modulation is applied to

the transmitter's microphone in the USB mode, the transmitter's output

frequency is increased whereas in the USB mode, the transmitter's output

frequency is decreased. The result in listening to the receiver is that when the

mode switch is in the proper position (either USB or LSB), a true

reproduction of single tone of modulation will result, and if the tone is

increased in frequency (such as a low-pitched whistle a high-pitched whistle)

you will hear the increase in the output tone of the receiver. If the incorrect

mode is selected, an increase in tone of a whistle applied to the transmitter

will cause a decrease in the resultant tone from the receiver.

Thus when a voice is used in place of a whistle or tone, in the proper

listening mode the voice will be received correctly whereas in the incorrect

mode, the voice will be translated backwards and cannot be made intelligible

by the voice lock control. When listening to an AM transmission, a correct

sideband is heard in either mode since both upper and lower sidebands are

received.

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Once the desired SSB mode has been selected, frequency adjustment

may be necessary in order to make the incoming signal intelligible, the

CLARIFIER control allows the operator to vary frequency above and below

the exact-center frequency of the received signal. If the sound of the

incoming signal is high or low pitched, adjust the operation of the

CLARIFIER. Consider it as performing the same function as a phonograph

speed control. When the speed is set to high, voices will be high-pitched and

if set too low, voices will be low-pitched. Also, there is only one correct

speed that will make a particular record procedure the same sound that was

recorded. If the record is played on a turntable that rotated in the wrong

direction (opposite sideband) no amount of speed control (CLARIFIER) will

produce an intelligible sound.

An AM signal received while listening in one of the SSB modes will

produce a steady tone (carrier) in addition to the intelligence, unless the SSB

receiver tuned to exactly the same frequency by the CLARIFIER control. For

simplicity it is recommended that the AM modes be used to listen to AM

signals.

ROGER BEEP

When your transceiver is on normal operation, your radio automatically

transmits the audio sign at the end of your transmission. The listener can note

easily that your transmission is over through the sign. Please note that this

ROGER BEEP transmits 0.15-second at the moment PRESS-TO-TALK

SWITCH KNOB is off.

Fig. 2.

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