Radiovastaanotin Suomalaisia radiovastaanottimien valmistajia/merkkejä | Lähteet | Navigointivalikko

Radio


radiolähetyksiäradiolähettimenradioaaltojaradiolähetinlähetin-vastaanotinantenniVirityspiirisuodattimettaajuisensignaalinesivahvistimellavahvistimillatransistoriradioidentransistoreihinSekoitusasteessaoskillaattorikantoaallonsinimuotoisestimoduloimallaanalogisiadigitaalisia







Transistoriradio sisältä


Radiovastaanotin on laite, jolla otetaan vastaan radiolähetyksiä. Radiovastaanotin ottaa vastaan radiolähettimen radioaaltoja ja muuttaa ne havaittavaan muotoon.[1] Laite, jossa on sekä radiolähetin että radiovastaanotin, on lähetin-vastaanotin.


Radiovastaanottimen ensimmäinen osa on antenni, joka siirtää vapaassa tilassa olevan radioaallon johtoon.[2]Virityspiiri ja suodattimet erottavat halutun, oikean taajuisen signaalin muista signaaleista, jotka se vaimentaa.[3] Signaalia yleensä vahvistetaan ensin esivahvistimella ja sen jälkeen muilla vahvistimilla. Nykyaikaisten transistoriradioiden vahvistimet perustuvat transistoreihin.


Sekoitusasteessa signaalin taajuus muutetaan suuremmaksi (lähetys) tai pienemmäksi (vastaanotto).[4] Laitteessa oleva oskillaattori kehittää kantoaallon, joka on sinimuotoisesti vaihteleva signaali. Oskillaattorin avulla tasavirtalähteen energiasta saadaan sekoitusasteen tarvitsema suurtaajuinen signaali.[5]


Lähettimessä kantoaaltoon liitetään lähetettävä signaali moduloimalla kantoaaltoa niin, että vastaanotin voi tämän muutoksen havaita vastaanotetussa lähetteessä. Käytössä on analogisia ja digitaalisia modulaatiotapoja. Tietoa sisältävä moduloiva - yleensä matalataajuinen - signaali, esimerkiksi puhe tai musiikki, on nimeltään kantataajuussignaali. Vastaanottimessa kantataajuussignaali erotetaan taas kantoaallosta sekoitusasteessa ja vastaanottimen elektroniikka muuntaa vaihtelevan jännitteen merkitykselliseksi tiedoksi tai aistikokemukseksi.[6]



Suomalaisia radiovastaanottimien valmistajia/merkkejä |


  • Asa

  • Helvar

  • Salora


Lähteet |


  • Lehto, Arto: Radioaaltojen maailma. Otatieto, 2006. ISBN 951-672-350-0.


Viitteet |



  1. ↑ Lehto 2006, s. 121.


  2. ↑ Lehto 2006, s. 124.


  3. ↑ Lehto 2006, s. 125.


  4. ↑ Lehto 2006, s. 127.


  5. ↑ Lehto 2006, s. 126.


  6. ↑ Lehto 2006, s. 129.








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