National_NC-270_(Manual操作说明书手册)

DESCRIPTION AND OPERATIONFIG.1 THE NC-270The National NC.270 receiver is designed to match an unbalanced 70u antenna and transmiseion line.Individual antenna coils are used on each band.The impedance match is obtained by use of a small primarycoupling winding on the antenna ooil with the exception that on the 6 meter band,the impedanoe match isobtained by means of a tap on the antenna coil.The rear apron of the NC.270 is illustrated inund may be connected to the receiver untennaFigure No.2.The NC-270 incorporates tuoterminals by connecting one of the lead wires tomethods of antenna connection,a smull cuaxiolthe antennu terminal,the other to the groundjack for use when shielded types of lead.in areterminal,although more satisfactory results willused.and a two terminal antenna strip suit.generally be obtained if a suitable balancedably marked A and G for use where individualto unbalanoed trunsformer type coupling islead wires are employed.The simplest antennaused.Many other types of antenna configura-is a single long wire antenna illustrated in Figuretions are available and beneficial under variousNo.3.When an antenna of this type is used,areception conditions.The subject of antennassuitable ground connection is recummended forand the matching of antennas to receivers is inbest results.Generally speaking,an antennaitself a major study.The ouner of the NC-2703H.Lbetueen 15 feet and 40 feet long should provideshould consult many of the excollent referencesample signal pick-up for most of the amateurpublished by the American Radio Relay Leaguebands in use.When the receiver is to be usedand other organizutions.In all cases where anpredominuntly on any one band,better resultsexternal.exposed antenna is employed,suitablecan always be obiained with one of the manyconsiderntion should be given to lightning protec-types of tuned antennas.The common doublettion for the sake of insuring safety to the operatoror half-itave antenna is illustrated in Figure No.and to the equipment.lITV ACEXTERNAL CONTROL CIRCUITLINE CORDSWITCH TERMINALSCOAXLAL ANTENNAo@o32 OHM SPEAKER GROUND ANTENNATERMINALSTERMINALSFIG.2 THE REAR APRON