FT-221and225MuTekFrontEnd维修电器原理图手册

muTek limitedband terminntfon for the input port of the ring nixer.FT221/225GT front endA ring mixer was chosen in preferenee to the more usual fetOur front-end bonrd hes been deeigned to bring the receiverfor two reasone:the moat obvious is that it ie much asaierperformmnce of the PE221 snd PT225 series trensceivers up toto schieve adequnte dynemie range with the ring.A eecond,a very high standard.The denign has evolved fron work done bypo8a1b1 y more subt1 e reseon.,1每tha专h向1 nherent1ybn1 ancedIan White,03SEK,and has been uned extensively for adwancedstrueture of the ring results in eancellstion of local oeeillatorexperimental work,and routine commundestion.an noise.As the phane locked tranalstion loop lo im the 221 end225 serle8卷ener8te8alte1 erge an no1s作u1 Aebnnd,.nbe1有needThe origimnl rf board fitted by Yaesu wuffern fron severalmixer1sn0 ndn to钉：defleieneles.The chief of these are distinot deafnaes (nolae1gr8not8~10d月rtn0tun阳nu】1n口rtod1f1 ed trannce1ror4)Proper ter1h两1no量h01x色r1s0 sentin1 for reproduc1b1mand s conefdereble ausceptability to strong-eigmmI overloedhtg的prt0T的na整prt杜on,Tha1018t0rm1nat0dw1h兼5Bproblems.Pitting s prenmplifier can help with the firatpsd:Me8nar西gAgO3 d broadband me专oh。There ie en0 ugh pow角rproblem but at the expense of dynamie renge.of course,'strongmtm11 nble a专the output of卡he clnen-A】o buffer to enaureg吐gm限1 problems ar8立0 t almay尊rec0gnlg®da哪uch,but1thproper mixer performanee.The nixer port whioh regulran nontthe pre8ent1eve】oi144WEz南et171切there can b0fe0 perat0r日csreful termination i8 the if output.The network here hea aeveralwho ere able to combletely disregard nignel handling probleme.funetions:it muet treneform the 50n output impedance of theof course there w1l always be those people (ineluding somediode ring to the optimun souree impedonce required by the nonfetmanufnotureret)who will remain convinced thet s little extreP0 et ampl上f1ri1t专enur8th8专t钻母1x种rh8春G8两rthlow noise presnplificetion cnm only do good......return,snd most importantly,it must provide n antinfnctorytermination for the whf and uhf produets genereted in the mixingThe HuTek rf board has been designed to eliminate the needpr0c888,Th810,TW阴81 pedance七raneformatton1。Aecomp:11hefor pr克npl1f生ers whi1gYs隔t1y1prov1 ng the dymmn1crg8ofw1th事n-new0rk,b11eher了choke prov1 des the eerth ret知n,the7gten。To overeo情the der时gn problem8pr88电nted hae requiredThe e8rle8 Ro network on the mixer output providen a monotondonl]enreful attent杜on to the11 nearit切of the nize0 and ampl1f生泰rineresaing return-1o8m with frequency,thue enauring proper1thp两rt1cu1rrG限r8 being欧ven to prop0rg1nd1 atribut杜on,termination nf the whf end uhf mixing produets.The rf atage ie a very low moine ion-implanted dunl-gate noefetThe mirer poet-emp t8 a low noise monfat which in opernted nt(38X88)This deviee ia empnbln of n gemuine (derioe)noise figurea high drain current for gooa intermoduletion performance.Althoughottr0und18.Weh两v8ch0 sen to专ra6 en with d灯nn1c物ngesome Angradntion of the no