{"id":19902,"date":"2024-04-23T17:53:43","date_gmt":"2024-04-23T16:53:43","guid":{"rendered":"http:\/\/www.crowave.com\/blog\/?p=19902"},"modified":"2024-04-23T17:53:43","modified_gmt":"2024-04-23T16:53:43","slug":"international-it14-19e","status":"publish","type":"post","link":"https:\/\/www.crowave.com\/blog\/2024\/04\/23\/international-it14-19e\/","title":{"rendered":"Radio prijemnik International IT14-19E"},"content":{"rendered":"<p>Danas je nabavljen prijenosni AM\/FM radio prijemnik oznake International IT14-19E, generi\u010dki kineski proizvod iz 1980\/90-tih godina.<\/p>\n<p>&nbsp;<\/p>\n<p><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_03.jpg\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19905\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_03.jpg\" alt=\"\" width=\"1000\" height=\"718\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_03.jpg 1000w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_03-768x551.jpg 768w\" sizes=\"auto, (max-width: 1000px) 100vw, 1000px\" \/><\/a><\/p>\n<p><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_05.jpg\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19907\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_05.jpg\" alt=\"\" width=\"1300\" height=\"692\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_05.jpg 1300w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_05-768x409.jpg 768w\" sizes=\"auto, (max-width: 1300px) 100vw, 1300px\" \/><\/a><\/p>\n<p><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_04.jpg\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19906\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_04.jpg\" alt=\"\" width=\"1300\" height=\"472\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_04.jpg 1300w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_04-768x279.jpg 768w\" sizes=\"auto, (max-width: 1300px) 100vw, 1300px\" \/><\/a><\/p>\n<p><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_07.jpg\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19909\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_07.jpg\" alt=\"\" width=\"600\" height=\"269\" \/><\/a><\/p>\n<p><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_06.jpg\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19908\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_06.jpg\" alt=\"\" width=\"1000\" height=\"474\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_06.jpg 1000w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_06-768x364.jpg 768w\" sizes=\"auto, (max-width: 1000px) 100vw, 1000px\" \/><\/a><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>Po vanjskom izgledu se vidi kako je ovdje rije\u010d o jo\u0161 jednom od tisu\u0107e modela malih jeftinih osnovnih modela AM\/FM prijemnika uvezenih iz Kine u posljednjih 30-tak godina. Ovakvi prijemnici danas vi\u0161e nemaju ni neku uporabnu, a jo\u0161 manje kolekcionarsku vrijednost, pa mogu bez velike \u0161tete poslu\u017eiti za neka elektroni\u010dka eksperimentiranja i upoznavanja sa prakti\u010dnom radio tehnikom.<\/p>\n<p>Za konkretan model IT14-19E nismo prona\u0161li nikakve podatke pa pogledajmo \u0161to se mo\u017ee saznati iz unutra\u0161nje konstrukcije.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_08.jpg\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19910\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_08.jpg\" alt=\"\" width=\"1300\" height=\"633\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_08.jpg 1300w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_08-768x374.jpg 768w\" sizes=\"auto, (max-width: 1300px) 100vw, 1300px\" \/><\/a><\/p>\n<p><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_09.jpg\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19911\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_09.jpg\" alt=\"\" width=\"1000\" height=\"1254\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_09.jpg 1000w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_09-768x963.jpg 768w\" sizes=\"auto, (max-width: 1000px) 100vw, 1000px\" \/><\/a><\/p>\n<p><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_10.jpg\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19912\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_10.jpg\" alt=\"\" width=\"1300\" height=\"699\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_10.jpg 1300w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_10-768x413.jpg 768w\" sizes=\"auto, (max-width: 1300px) 100vw, 1300px\" \/><\/a><\/p>\n<p><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_11.jpg\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19913\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_11.jpg\" alt=\"\" width=\"1300\" height=\"575\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_11.jpg 1300w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_11-768x340.jpg 768w\" sizes=\"auto, (max-width: 1300px) 100vw, 1300px\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_12.jpg\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19914\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_12.jpg\" alt=\"\" width=\"1300\" height=\"439\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_12.jpg 1300w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_12-768x259.jpg 768w\" sizes=\"auto, (max-width: 1300px) 100vw, 1300px\" \/><\/a><em><span style=\"color: #00ffff;\">Mre\u017eni transformator (slika lijevo) te dvije diode i filtarski kondenzatori u krugu ispravlja\u010da napona napajanja (slika desno).<\/span> <\/em><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>\u010citav ure\u0111aj se bazira na svega osam tranzistora \u0161to je minimum za neki upotrebljiv AM\/FM prijemnik. Prvo \u0107emo razlu\u010diti koji su tranzistori u VF krugovima (tuneri i MF poja\u010dala), a koji rade u NF krugovima, odnosno kao audio poja\u010dala.<\/p>\n<p>Oko NF audio poja\u010dala nema puno dvojbe. Sastoji se od \u010detiri NF tranzistora smje\u0161tena na donjem dijelu plo\u010dice:<\/p>\n<ul>\n<li>Q5: S9014 (NPN) &#8211; pretpoja\u010dalo<\/li>\n<li>Q6: S9015 (PNP) &#8211; driver<\/li>\n<li>Q7: S9012 (PNP) i Q8: S9013 (NPN) &#8211; komplementarni push-pull izlazni stupanj<\/li>\n<\/ul>\n<p>Time preostaju jo\u0161 \u010detiri VF tranzistora tipa 2SC1417 za AM\/FM tunere i MF poja\u010dala. Ove NF i VF garniture tranzistora ve\u0107 smo susretali kod vi\u0161e sli\u010dnih malih AM\/FM prijemnika. U FM tuneru bi kao neki minimum svakako morala raditi dva tranzistora, a u AM tuneru jedan tranzistor, \u010dime onda za MF poja\u010danje preostaje samo jedan tranzistor. Nigdje ne uo\u010davamo kerami\u010dke filtre, a vidimo da je ugra\u0111eno svega \u0161est VF lon\u010di\u0107a \u0161to je opet minimum za superheterodinski AM\/FM prijemnik.<\/p>\n<p>Kod ovako reduciranih sklopova prijemnika barem dva tranzistora su zajedni\u010dka za AM i FM krugove:<\/p>\n<ul>\n<li>Q1: 2SC1417 (NPN) &#8211; RF poja\u010dalo FM tunera<\/li>\n<li>Q2: 2SC1417 (NPN) &#8211; samoosciliraju\u0107i mje\u0161a\u010d FM tunera<\/li>\n<li>Q3: 2SC1417 (NPN) &#8211; samoosciliraju\u0107i mje\u0161a\u010d AM tunera i 1. MF poja\u010dalo za FM<\/li>\n<li>Q4: 2SC1417 (NPN) &#8211; 1. MF poja\u010dalo za AM i 2. MF poja\u010dalo za FM<\/li>\n<\/ul>\n<p>Sli\u010dnu konstrukciju smo vidjeli primjerice kod prijemnika <a href=\"http:\/\/www.crowave.com\/blog\/2022\/06\/05\/fm-am-radio-sk-1001-gelka\/\" target=\"_blank\" rel=\"noopener noreferrer\">SK 1001 Gelka<\/a>.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_01.gif\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19903\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_01.gif\" alt=\"\" width=\"1174\" height=\"637\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_01.gif 1174w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_01-768x417.gif 768w\" sizes=\"auto, (max-width: 1174px) 100vw, 1174px\" \/><\/a><em><span style=\"color: #00ffff;\">Vjerojatna blok shema AM\/FM prijemnika SK 1001 Gelka.\u00a0<\/span> <\/em><\/p>\n<p>&nbsp;<\/p>\n<p>Me\u0111utim, iako je i Gelka tek osnovni model prijemnika sa minimalnim brojem elemenata, vidimo da se ovdje u VF krugovima nalazi jedan VF lon\u010di\u0107 vi\u0161e, a i NF poja\u010dalo ima jedan tranzistor vi\u0161e. S obzirom da nemamo elektroni\u010dku shemu na\u0161eg prijemnika IT14-19E pretpostavljamo da je u\u0161teda napravljena na na\u010din da se za FM MF poja\u010dala koristi aperiodski stupanj sa tranzistorima Tr3 i Tr4 u RC vezi bez MF transformatora. Ovo svakako utje\u010de na slabiju selektivnost FM prijema, osim ako su ulazni i izlazni FM MF transformatori (1. MF TRAFO, 2. MF TRAFO) izvedeni sa vi\u0161e selektivnih LC krugova. To pak vjerojatno nije slu\u010daj jer bi onda na MF transformatorima imali vi\u0161e pode\u0161avaju\u0107ih induktiviteta (feritnih jezgrica). U svakom slu\u010daju do sada nisam nai\u0161ao na tvorni\u010dku shemu AM\/FM radio prijemnika koji bi imao tako reducirane MF krugove no ne vidim kako druga\u010dije objasniti postojanje samo \u0161est VF lon\u010di\u0107a.<\/p>\n<p>Isto tako izbacivanje jednog stupnja audio pretpoja\u010danja svakako utje\u010de na lo\u0161iju osjetljivost prijema jer takvo reducirano poja\u010dalo ne mo\u017ee poja\u010dati demodulirane signale niskih razina. Kad se tome pridodaju ugra\u0111ene relativno male AM i FM antene, prijemnik poput ovog mo\u017ee uhvatiti samo ja\u010de (lokalne) AM\/FM radio postaje, a to je u ve\u0107ini slu\u010daja i dovoljno za neki priru\u010dni radio kojem je zadatak tek da popuni ti\u0161inu u kakvoj radnoj prostoriji.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><a href=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_02.gif\" rel=\"lightbox[19902]\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-19904\" src=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_02.gif\" alt=\"\" width=\"1162\" height=\"630\" srcset=\"http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_02.gif 1162w, http:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_02-768x416.gif 768w\" sizes=\"auto, (max-width: 1162px) 100vw, 1162px\" \/><\/a><em><span style=\"color: #00ffff;\">Vjerojatna blok shema AM\/FM prijemnika International IT14-19E.\u00a0<\/span> <\/em><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>Za jeftine kineske prijemnike iz 1990-tih i kasnijih godina prakti\u010dno je nemogu\u0107e na\u0107i originalne tvorni\u010dke sheme. To je \u0161teta, jer se do tog razdoblja ve\u0107 do\u0161lo do vrhunca u redukciji i pojednostavljenju konstrukcija AM\/FM prijemnika kako bi bilo utro\u0161eno \u0161to manje (skupljih) dijelova i kako bi se onda cijenom moglo konkurirati na svjetskom tr\u017ei\u0161tu. Bilo bi zanimljivo vidjeti koji su sve trikovi bili primjenjivani da se iz \u0161to manje elemenata izvu\u010de \u0161to vi\u0161e performansi.<\/p>\n<p>Naravno da je politika \u0161to ve\u0107e u\u0161tede prisutna kod konstrukcija prijemnika od samog po\u010detka njihovog razvoja, no za 1990-te i kasnije godine ipak o\u010dekujemo da su i najjeftiniji AM\/FM prijemnici puno bolji od onih najjeftinijih od prije 20 ili 30 godina. Ipak, na ovom primjeru Internationala IT14-19E vidimo da to nije bilo tako, te su unato\u010d vi\u0161estrukom pojeftinjenju poluvodi\u010da i drugih elektroni\u010dkih komponenti najjeftiniji radio prijemnici i dalje shematski ostali gotovo isti, s tom razlikom \u0161to su samo ugra\u0111eni moderniji elektroni\u010dki elementi.<\/p>\n<p>Tek tamo negdje od 2010-tih godina u\u0161li su u masovnu upotrebu specijalizirani radio \u010dipovi koji su nudili daleko bolje performanse nego se to posti\u017ee jednostavnim tranzistorskim prijemnicima, a tako\u0111er su bili i jeftiniji od cijene diskretnih komponenti koje su zamjenjivali. Danas kada kupite neki najjeftiniji AM\/FM prijemnik sasvim sigurno \u0107e se bazirati na jednom takvom specijaliziranom \u010dipu u kojem se dio signala obra\u0111uje digitalno.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Danas je nabavljen prijenosni AM\/FM radio prijemnik oznake International IT14-19E, generi\u010dki kineski proizvod iz 1980\/90-tih godina. &nbsp; &nbsp; &nbsp; Po vanjskom izgledu se vidi kako je ovdje rije\u010d o jo\u0161 jednom od tisu\u0107e modela malih jeftinih osnovnih modela AM\/FM prijemnika uvezenih iz Kine u posljednjih 30-tak godina. Ovakvi prijemnici danas vi\u0161e nemaju ni neku uporabnu, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":19905,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[],"class_list":{"0":"post-19902","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-radio","8":"czr-hentry"},"jetpack_featured_media_url":"https:\/\/crowave.com\/blog\/wp-content\/uploads\/2024\/04\/international_it14_19e_03.jpg","_links":{"self":[{"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/posts\/19902","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/comments?post=19902"}],"version-history":[{"count":1,"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/posts\/19902\/revisions"}],"predecessor-version":[{"id":19915,"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/posts\/19902\/revisions\/19915"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/media\/19905"}],"wp:attachment":[{"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/media?parent=19902"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/categories?post=19902"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.crowave.com\/blog\/wp-json\/wp\/v2\/tags?post=19902"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}