AM and FM Radio Explained

Yesterday, I gave you a pretty confusing explanation of how AM (amplitude modulation) and FM (frequency modulation) worked.

Here’s a film from our military that explains how the two bands differ.

They also explain the carrier frequency (or rest frequency), which is the frequency you tune your radio when you listen to a particular radio station, such as 90.7 MHz when you want to listen to Fordham’s own WFUV-FM. In the case of FM, the frequency is modulated but centered at that rest frequency.

Radio Programs from the “Golden Age”

If you’re interested in listening to radio programs from the “Golden Age of Radio,” there’s an overwhelming collection available at the Internet Archive. You’ll find a lot of dramas, news, comedy and variety programs available.

For other classes where I get to indulge radio more, I usually audition these programs to get a sense of the different formats available.

  • Amos and Andy, “Andy Reads a Law Book,” July 3, 1929. A comedy that traffics in some pretty racist stereotypes of the not-so-distant past. However, note that the comedy follows the straight-man and the stooge template of comedy duos and is entirely premised on literacy.
  • Franklin D. Roosevelt’s First Fireside Chat, March 12, 1933. This excerpt of FDR’s first radio address to the nation explains why he chose to close the banks: it’s so that people don’t all take their money out at the same time. Note his use of two opposite tropes: fear vs. faith.
  • Rudy Vallee on the Royal Gelatin Hour, August 25, 1938. This singer, and bandleader of the Connecticut Yankees, entertains his audience in classic variety show style. As a recreational softball player, I appreciate the interview with the softball player.
  • CBS News, “London After Dark,” August 25, 1940. This dispatch gives radio listeners in the US a sense of what it was like in London during the “Blackout,” when the entire city was kept in the dark so that German bombers couldn’t find their targets. This proves the adage that radio is the most visual of all the media.
  • Burns and Allen, “George Goes to College,” November 29, 1945. George and Gracie are married and living in Hollywood. A lot of the humor is predicated on George being old (he was 49 years old but only half way through his life at the time), Gracie being dumb, and Jack Benny being cheap. Only that last bit was probably true. Also, I don’t know about you but my college didn’t have such an obsession with popularity, but then again, I went to a state school.

Also, if you’re interested in the difference between AM and FM radio, and how static (interference) affects the reception, here’s a US Army film from the 1960s.

I love this stuff so it makes sense to me, but if you need to have something explained, let me know.

Empire of the Air: The Men Who Made Radio

As my presentation on radio technology was longer than I had expected, we didn’t have time to watch the Ken Burns documentary Empire of the Air: The Men Who Made Radio (1991). You can watch this on your own in one of the following ways:

Or if you can read the book by Tom Lewis on which the film is based.

If you watch it, here’s a few things to note:

  1. You should only watch the first half of the film, just before radio moves from point-to-point communication to “broadcasting”
  2. Norman Corwin was a famous writer of radio programs, many during the so-called Golden Age of Radio.
  3. Susan Douglas wrote Listening In: Radio and the American Imagination and Eric Barnouw wrote on all broadcast media, including radio, but is best known for Tube of Plenty tome on television.
  4. Common synonyms for radio include “wireless,” “crystal set,” and “radio telephone.” 
  5. The song about radio at the end of the first part was one that was taking advantage of the radio craze in the 1920s. Honestly, will you be able to “love her” by radio?