January, 2000: Hello Monitoring Times Readers!

    Introduction to the "Radio Restorations" Column; the consumer radio boom of the 1920s; crystal detectors; vacuum tube detectors: grid leak and regenerative.

February, 2000: Battery Sets of the 1920s

    Construction and operation of the Crosley 50, a typical "low end" regenerative receiver; design and operation of the "3 dialer" TRF receiver; how Atwater Kent and Freshman sidestepped the Neutrodyne patent. The superheterodyne design.

March, 2000: The First A.C. Sets

    The annoyance of batteries; battery eliminators; new tubes that made "plug in" radios possible; the types 26 and 71A; introduction of the first cathode tube (type 27); construction of the Atwater Kent 42, an early a.c. set of TRF design; the Radiola 60, an early a.c. superheterodyne.

April, 2000: The Screen Grid Revolution

Feedback control: introducing the screen grid; types 24 and 24A tubes; screen grid radio marketing; variable mu tubes; book review: Machine age to Jet Age III--Radiomania's Guide to Tabletop Radios 1930-1962 by Mark Stein.

May, 2000: The Radio Becomes a Home Appliance

    Comparison of the 3-dialer and early a.c. set with the integrated construction of a 1930s TRF: tuning caps on same shaft with r.f. tubes grouped around it; power supply now on radio chassis; speakers now compact and in cabinet; cathedrals, tombstones, living room consoles; reader comments; review of Xtal set society publications.

June, 2000: Depression Downsizing

    Introduction of the pentode: how it works, increased sensitivity makes possible smaller sets; the International Kadette, a minimal depression set; series string heater issues; the a.c.-d.c. idea.

July, 2000: A.C.-D.C. Evolution

    Introduction of the superheterodyne circuit, Bakelite cabinet, PM speaker, "all American five" tube complement, built in loop antenna; design of the 3-way portable; 1.5-volt tubes; transformer-powered sets; 6.3-volt tubes.

August, 2000: New Twists on Tuning

    In early 1940s manufacturers begin to stress features rather than performance; evolution of tuning dials; introduction of short-wave coverage; electrical and mechanical pushbuttons; tuning eyes; other interesting tuning gimmicks.


April, 2003: A short History of Vacuum Tubes

    Tube bases: at first: four stubby contacts and locking pin, shift from brass to Bakelite; shift to long friction contacts and no locking pin; screen grid and cathode require 5-pin base and grid cap; envelope styles: pear shaped, "ST," "GT," metal; Octal and Loktal bases, evolution of tube numbering systems.

October, 2005: How Many Volts to Light a Tube?

    Tube evolution: early 1920s tubes such as 01A and 71-A with 5-volt filaments to operate from 6-volt auto batteries; dry cell tube types with 1.1 or 3.3-volt filaments; unsuitability of 01-A (too much hum) for later plug in sets, but 71-A suitable as audio output tube; new tubes needed for r.f. amplifiers, detector, first audio; type 26 rf amplifier had high current, 1.5-volt filament to provide "thermal inertia;" type 27--which introduced the cathode--developed for detector and first audio; why the 27 was given a 2.5-volt heater; advent of 6.3 volt--and later 12.6 volt--tubes for auto radios; higher voltage heaters for a.c.-d.c. sets; 1.4 volt tubes for battery portables.

November, 2005: The First Broadcast Receivers

    Recap of 05 AWA Conference; crystal set predated broadcast era; vacuum tube era, spurred by wartime development, already established when broadcast era began; the popular regenerative receiver design; firing up a Crosley 50. (See conclusion of January, 2006 column in the HQ-120-X series for discussion of the 3-dialer era and the first plug-in sets; see conclusion of February, 2006 column in the HQ-120-X series for discussion of superheterodynes, grand living room consoles, compact table models, tombstones and cathedrals.)

April, 2006: A.C.-D.C. "Depression Radios"

    Eliminating the power transformer; the design of the "Kadette Universal TRF," the first A.C.-d.c. set; the next generation: new tube nomenclature, superheterodyne circuit; ballast tube, filter circuit with speaker field, magnetic vs dynamic speaker, hot chassis safety hazard; introduction of molded plastic cabinets; introduction of compact tube types and PM speakers.

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