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Lil’BrownRadiosNeedLoveToo!
TheAirline1939MidgetARadiowithUniqueTuning…
ApresentaAonbyBartLee,K6VKfortheCaliforniaHistorical
RadioSociety,©2017
CosmeAcRestoraAonofthe1939AirlineAA4
Airline04BR-420B{?};RadioMuseum.orgID47498withSchemaAc.(ButthisisanAll-AmericanFour[!])
UsefulCompoundsforBakeliteRestoraAon
Also,Brasso(butbewareofabrasivesinit),silverpolishes,Simichromepolishandtoothpaste.
TheCabinetPolished
…withLotsofElbow-greaseandQ-ApCleaningofNooksandCrannies… Butwhat’sInside?
Thebakeliteisaburlpaeernofbrownandblackswirls–UnderstatedElegance!
ThisRadioWorked!
Noneedtore-capordiagnose80yearoldtroubles--that’simpressiveengineering!
Where’stheVariableTuningCapacitor?
AVariableInductanceTunes:
Thisis“permeability”tuningoftheinductancewithaferritecoreorslug.
Sinceit’saSuperhet,theLocalOscillatorNeedsTuningToo
TheCord-LinkedVariableInductancesTuneTogether,attheIFOffset.
MovingFerritesTunetheCoilAgainstaFixedCapacitor;Why?
MidgetRadiosMustSaveSpace!
• Atwo-gangedtuningcapacitortakesupalotofroom,butthisisaverysmallradio.
• Italsorunsplentyhot,andheatcanwarpaluminumcapacitorplates…
• AndlookingtoWWII,Aluminumwasbeeerputtousetomakeaircran...
• Butmostlikely,thisradiohadtobecuteandsmalltoselltotheladyofthehouse!
SevenInchesWideby5InchesHighby4InchesDeep(188x124x102mm)
Fromthe1939-’40MontgomeryWardcatalog;courtesyRadioMuseum.org
ItFitsEverywhere
• ThisisaperfectlielekitchenradioforlisteningtoArthurGodfreyinthemorning.
• Thisisaperfectbedsideradioforonelastprogramintheevening:“Saygoodnight,Gracie.”
• Thisisaperfectkid’sradioforlisteningtotheLoneRangerandevenJeanShepherd.
• Youcan’tgowrongfor$5.73[!!]the1939–’40catalogprice:Buythree!!
ASimilarPostWarRadio,AA5
NoteGangedInductors>>
SameFirstThreeTubes:
AboutOneWaeAudioOutput.
HowFourTubes?
• Intheradioexamined,thelastaudiotubeisa35L7,apentodeamplifierandadioderecAfier
• Thethree12volttubesprovidemixingandIF• Adroppingresistortakesthelinevoltageforthefilamentsdowntoabout70volts:
RadioManufacturers’AssociaAon
“Approved,”soIguessit’sOK–justdon’tdropitinyourbathtub!
PermeabilityTuningfromthe1930s• AnotedphysicistworkedouttuningbymagneAcpermeability
ininductancesin1933:W.J.Polydoroff,“Ferro-InductorsandPermeabilityTuning”ProceedingsoftheInsAtuteofRadioEngineers,Issue5,May1933;seealsoNature133,956-956(23June1934).
• CommercialadopAonsuchastheAirlinemidgetfollowed.• Permeabilitytuningwasespeciallyusefulincarradiosthat
couldthendowithoutbulkytuningcapacitors.ThistuningpersistedinvehicleradiounAlthecomingofdigitaltuning.
• Someamateurgearusedpermeabilitytuning,e.g.,Ten-TectransceiverssuchastheCorsairII.
• CollinsradiopioneeredpermeabilitytuninginWorldWarTworadios.ThelaterR-390isaclassicinstance.
PermeabilityTuningGoestoWar
ThismidgettacAcalandcovertshortwavereceiverdatesfromWorldWarTwo(1943);itsNavynomenclaturewasRBZ.Inthisversioncovering5to13MHz,itissaidtohavebeenmadeavailabletoanA-NaziforcesinEurope,especiallyformonitoringtheBBCandsecretmessages.Emersonmanufacturedit.See:www.cryptomuseum.com/spy/rbz/index.htm
PleaseAddMoreInformaAon!
CorrecAons,suggesAonsandamplificaAonsarewelcome.Sendto:[email protected].
ThispresentaAoniscopyrightBartLee,2017(whoisaFellowofthe
CaliforniaHistoricalRadioSociety)butanyreasonableusemaybemadeofitinfurtheranceofradiohistoryandthehistoryofthistechnology,respecAngbyproperaeribuAonitsauthorshipandintegrity.Allmoralrightsareasserted.
73deBart,K6VK##
Seewww.californiahistoricalradio.com
