crt superstar900ït manual (15) wm

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RECEIY INC SSB SIGNALS

Therc arc four lypcs of signals prcscntly uscd for Communications in thc Citizcns Band : FM. AM, USB and i.SB. W hen thc MODĘ switch on your unit is placcd in thc AM position. only standard doublc-sidc band and in FM position. only frequency dc\ iation. fuli carricr signals will bc dctcctcd. An SSB signal may bc rccogni/cd while in thc AM or FM modÄ™ by its characteristic "Donald Duck" sound and thc inability of thc dctcctor to producc an intclligiblc output. The USB and LSB modcs will dctcct upper sidc band and lowcr side band rcspecthcly. and standard AM signals.

SSB rcccption diffcrs front standard AM rcccption in tliat an SSB rcccivcr docs not rcquirc a carricr or oppositc sidc band to producc an intclligiblc signal. A singlc-sidc band transmilted signal oonsists only of thc upper or thc lowcr sidc band and no carricr is transmittcd. The climination of thc carricr front thc AM signal hclps to eliminatc thc biggest cause of whistlcs and tonos hoard on channcls which make evcn modcratcly strong AM signals unrcadablc. Also. SSB lakcs only half thc spacc of an AM channcl. thcrcforc two SSB comcrsations will fil into cach channcl, cxpanding thc 40 AM channcls to 80 SSB channcls. The rcduction in channcl spacc rcquircd also hclps in thc rcccivcr bccause only half of thc noisc and intcrfcrcncc can bc rcccivcd willi 100% of thc SSB signal.

An SSB signal may bc rccehcd only when thc listening sanie modc. In other words. an upper sidc band signal (USB) nta only if thc rcccivcr is functioning in thc USB position.

Oncc thc desired SSB modc has bccn sclcctcd. frcqucncy adjustnient may bc ncccssary in order to make thc incoming signal intclligiblc. The F1NF/COARSF eon troi allows thc operator to vary frcqucncy abovc or bclow thc cxact frcqucncy of thc channcl. If thc sound of thc inconting signal is high or Iow pitchcd. adjusl thc operation of thc FINF/COARSF.

Considcr it as performing thc same function as a phonograph speed control. When thc speed is set too high. voiccs will bc high-pitehed and if set too Iow . voiee w ill bc low-pitched. Also. therc is only one correct speed tliat will make a partieular record producc thc same sound tliat was rccordcd. If thc record is played on a turntablc tliat is rotated in thc w rong direction (oppositc sidc band) no amount of speed control (FINF/COARSF!) w ill producc an intclligiblc sound.

An AM signal rccehcd while listening in one of thc SSB modcs w ill producc a steady tonÄ™ (carricr) in addition to thc intclligcncc. unless thc SSB receivcr is tuncd to cxaclly thc same frcqucncy by thc FINF/COARSE control. For simplicity. it is rccommcndcd tliat thc AM modcs bc uscd to listen to AM signals.

functioning in thc madÄ™ intclligiblc

If a lowcr sidc band (LSB) signal is hcard w hen thc rcceivcr is in thc USB modc. no amount of tumng will make thc signal intclligiblc. The rcason for this may bc understood if you considcr tliat when thc modulation is applied to thc transmittefs nticrophonc in thc USB modc. thc transmitter output frcquency is incrcascd whcrcas in thc LSB modc thc transmitter's output frcqucncy is dccrcascd.

The rcsult in listening to thc rccciver is tliat when thc MODF switch is in thc proper position (cither USB or LSB). a truć rcproduction of a single tono of modulation w ill rcsult. and if thc tonc is incrcascd in frcquenoy (such as a Iow-pitchcd whistlc ora high-pitehed whistlc) you w ill hear thc inerease in thc output tonc of thc rcceivcr. If thc incorrcct modc is sclcctcd. an inercasc in tonc of a w histlc applied to thc transmitter w ill cause a dccrcasc in thc resultant tonc from thc recehcr.

Thus w hen a voicc is uscd in place of a whistlc or tonc. in thc proper listening modc thc Yoice w ill bc rccehcd corrcctly w hcrcas in thc incorrcct modc. thc voice w ill bc translated baekwards and cannot bc madÄ™ intclligiblc by thc FINH/COARSK control. When listening to an AM transmission. a correct sidc band is hcard in cither modc siÅ„ce both upper and low cr sidc bands arc rcceh cd.

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