Tšebeliso ea Sefe ea 21.4MHz ho Walkie-Talkie Field

Tšebeliso ea Sefe ea 21.4MHz ho Walkie-Talkie Field

Sesefa sa 21.4MHz hangata se sebelisoa e le sefe ea maqhubu a mahareng (IF) ho li-walkie-tse amohelang lipuo, 'me tšebetso ea sona e laola ka kotloloho matšoao a mabeli a mantlha a -talkies: khetho le kutlo.

Re tla hlalosa ka botebo ho tsoa likarolong tse latelang:

1. "Intermediate Frequency" ea Walkie-Talkie ke efe?

Ho fihlela tšebetso e ntle, li-walkie{0}}talkies (hammoho le baamoheli ba bang ba superheterodyne) ha li holise le ho theola mats'oao a radio frequency (RF) ka kotloloho (mohlala, 400-470MHz). Ho e-na le hoo, ba nka mehato e latelang:① Ho kopanya: Letšoao la RF le amoheloang le phahameng le kopantsoe le lets'oao le hlahisoang ke oscillator ea lehae.

Molemo oa sebopeho sa "superheterodyne" ke hore boholo ba phaello le khetho (bokhoni ba ho sefa ho kena-kenana le mocha o haufi) bo finyelloa ke karolo ena e tsitsitseng ea IF, ho etsa hore moralo oa potoloho o be o tsitsitseng le o sebetsang hantle.

2. Hobaneng 21.4MHz?

21.4MHz ke mofuta o tsebahalang haholo oa IF frequency ho lihlopha tsa VHF/UHF (ho kenyeletsoa le lihlopha tse sebelisoang ke walkie{1}}talkies). Mabaka a eona a nalane le tekheniki a kenyelletsa:

Lethathamo la liindasteri tse holileng: Bakeng sa maqhubu a 21.4MHz, ho na le lihloela tse ngata tse holileng, tse tsitsitseng, le tse tlase{1}}, liamplifi, le likarolo tse ling tse teng.

Ho leka-lekana pakeng tsa ts'ebetso le litšenyehelo: Lekhalo lena le phahame ka ho lekaneng ho thibela ka katleho ho sitisa setšoantšo (ho kena-kenana le kamohelo e tloaelehileng); ka nako e ts'oanang, e tlase ka ho lekana ho thusa ho rala le ho etsa lihloela tse phahameng-Q (quality factor) (joalo ka lifilthara tsa kristale le lihloela tsa ceramic).

Histori ea lefa: Khafetsa ena esale e sebelisoa indastering ea likhokahano ka lilemo tse mashome, 'me li-walkie tse ngata tsa khale-li-talkie chips le litharollo li entsoe ho latela makhetlo ana a mahareng.

3. Karolo ea Konokono ea Sefe ea 21.4MHz ho Walkie-Talkies

Karolong ea 21.4MHz IF, filthara ke "molebeli oa heke" oa 'nete. Karolo ea eona e bohlokoa:① Ntlafatsa Khetho

Mosebetsi: Khetho e bolela bokhoni ba moamoheli ba ho khetholla lets'oao le lakatsehang ho tsoa ho mats'oao a mangata le ho hatella matšoao a tšitiso a haufi.

E sebetsa joang: Filter ea 21.4MHz e na le moepa oa karabelo o moepa haholo (hangata joalo ka "lebota la litene"). E lumella feela karolo ea matšoao e nang le 21.4MHz e le setsi le bandwidth e nepahetseng haholo ho feta (mohlala, ± 6.25kHz, ± 7.5kHz, ± 12.5kHz e sebelisoang hangata ho walkie -talkies, e tsamaellanang le libaka tse fapaneng tsa likanale).

Phello e sebetsang: Ha liea-le-moea tse peli tse nang le maqhubu a haufi haholo li phatlalatsa ka nako e le 'ngoe, walkie-talkie e nang le molumo o phahameng-sefe ea 21.4MHz e khona ho utloa molumo oa seea-le-moea se lebeletsoeng, ha e ntse e hatella lets'oao la seteishene se seng se haufi ho qoba ho bua. Ntle le sefe ena kapa sefe e sa sebetseng hantle, o tla utloa lerata la "channel crosstalk".

② Ntlafatsa Kutloelo-bohloko

Mosebetsi: Kutloisiso e bolela bokhoni ba moamoheli ba ho amohela matšoao a fokolang.

Kamoo e sebetsang kateng: Pele o holisa lets'oao la IF, sefe se sebelisoa ho thibela-ho{1}}lerata le tšitiso pele. Ka tsela ena, amplification ea mantlha ke "hloekile" lets'oao le molemo ka boeona. Haeba katoloso e etsoa ntle le ho sefa,{4}kantle ho-lerata la sehlopha le lona le tla matlafatsoa, ​​ka hona ho tima lets'oao le sebetsang le fokolang.

Phello e sebetsang: E ​​lumella walkie{0}talkie ea hau ho boloka puisano e utloisisoang le ha u le hole kapa ka mats'oao a fokolang.

4. Mefuta ea Li-filters tsa 21.4MHz

Ho li-walkie-talkies, lihloela tse tloaelehileng tsa 21.4MHz li kenyelletsa haholo mefuta e latelang:

Sefe ea Ceramic:

Likarolo: Theko e tlase, boholo bo nyane, ts'epo e phahameng, 'me ha ho na phetoho e hlokahalang.

Lisebelisoa: E sebelisoa haholo lipakeng tsa-ho{1}}ho{2}}tlase-li-walkie{3}}, 'me tšebetso ea eona e lekane ho fihlela litlhoko tse tloaelehileng. Bophahamo ba eona ba bandwidth le sebopeho sa eona (sesupo sa ho lekanya botebo ba sefahla) hangata li mpe ho feta li-filters tsa kristale empa li betere ho feta li-filters tsa LC.

Sefe ea Crystal:

Likarolo: E na le boleng bo holimo haholo ba Q, kahoo khetho e ntle haholo, 'me sebopeho sa sebopeho se haufi haholo le boemo bo loketseng.

Lisebelisoa: Hangata e sebelisoa-litabeng tsa litsebi tsa ho bua-kapa liketsahalong tse hlokang matla a phahameng haholo a ho thibela{2}}tšitiso. Litsenyehelo li phahame ho feta tsa li-filters tsa ceramic.