Lil’ Brown Radios Need Love Too! · Lil’ Brown Radios Need Love Too! ... • Collins radio pioneered permeability tuning in World War Two ... Emerson manufactured it.

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