In a Nutshell
This model was the first to sport Zenith's later trademark circular design with the tone control centered in front of the speaker. It was Zenith's first miniature tube radio and one of the first to replace the rectifier tube with a selenium rectifier (today normally replaced again with a Si diode). It's a rare radio with two FM bands, one of which today is used for GLMRS (General Land Mobile Radio Service)

Introduction:
Edwin Howard Armstrong [1890-1954] invented nearly all things radio, so the superheterodyne receiver in 1918 and FM radio in 1933. In grief and despair after being abandoned by his wife of 31 years, Marion (she was the secretary of the president of RCA, David Sarnoff) and tired from his life-long legal patent battles mainly against Sarnoff, Armstrong jumped from the window of his 13th-floor apartment in New York on Jan.31, 1954. He was inducted into the National Inventors Hall of Fame in 1980.
In 1941, the first commercial radios with FM band came on the market, but it was Sarnoff who boykotted Armstrongs success story, pushing his community television business to occupy Armstrongs FM frequencies from 42 to 50 MHz. After World War II, the "old FM" band was phased out in favor of the new band as we know it now. From 1946 to 1948, most AM/FM radios (costing about two times more than an AM radio) had both the new and the old FM bands. So did Zenith's 7H820, but only for a short time, after which the old band was omitted. The double FM sets are quite rare. Today the 30-50 MHz "VHF low" band is not totally empty. Reserved for GLMRS (General Land Mobile Radio Service), a wide variety of stations can be heard on this band, including businesses, federal, state, and local governments, law enforcement agencies, various industrial radio services - and, yes - baby monitors. Other highlights: Zenith's first circular dial radio with centered tone control, first all-miniature tube radio, early use of Selenium rectifier instead of a tube, inductive FM tuner.

Additional information:
   ref. 1:    http://www.radiomuseum.org/r/zenith_7h820_ch7e01.html
   ref. 2:    http://padgett.performanceresearch.us/radio/7h820.htm
   ref. 3:    http://youtu.be/VjofFQ1GroE

About my radio:
The cabinet has been rejuvenated with Arrow-Magnolia Glayzit bakelite polish, the chassis recapped and serviced (see pict.19). It has all 3 (4) of its original plastic knobs, and the original double loop antenna and back plane. All 7 tubes have been optimized using my stock, including 4 branded Zenith, the Se-rectifier has been replaced by a Si diode.
I treated all moving parts with contact spray. The radio plays loud and clear on AM/BC and both FM bands (I listened to 2-way radio on FM1 too). Watch a youtube video [ref.3] or click on pict.27). Please e-mail me (Kris) for any questions, ich spreche Deutsch, je parle Français.

Here are the specifications:

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