How FM Radio Works: A History and Exploration of Frequency Modulation

Today, we take FM radio broadcasts for granted, and some people even insist radio broadcasts are dead (hint: they’re not even close to dead). However, a gigantic amount of ingenuity went into developing frequency modulation, largely due to the efforts of one inventor and his staff. In this video, I’ll detail some of the history, the struggles, and the reasoning behind FM broadcasting. Along the way, you’ll see something you probably haven’t before: an FM radio signal in slow motion so the mechanics are clearly visible.

Major Edwin Howard Armstrong, who also developed the superheterodyne circuit that revolutionized radio receivers, spent years experimenting to make FM the force of nature it became, and always relished coming back to give it to naysayers with an epic mic drop. AM broadcasters and the corporate interests working to develop television may have gotten the upper hand on Armstrong, but he got the last laugh with stereo FM igniting a very real “golden age” for the technology, as well as FM being utilized for the audio portion of North America’s NTSC analog television standard. Armstrong never had the opportunity to see his creation’s heyday; he took his own life in 1954 as the overwhelming stress of drawn-out litigation over infringement of his FM patents crushed his mental health and drained his financial resources. Armstrong’s wife Marion, ever his supporter, continued his fight and saw every single case either decided in his estate’s favor or settled out of court.

My landing page:
https://BroadcastBlueprint.com

The inspiration for this video, from ‪@vwestlife‬:
   • MPX Filter - What does it actually fi...  

Nyquist-Shannon sampling theorem:
   • Nyquist-Shannon; The Backbone of Digi...  

My video on audio processors:
   • How Audio Processing is Used in Broad...  

Empire of the Air: The Men who Made Radio (PBS official site):
https://www.pbs.org/kenburns/empire-air/

Written and edited by Drew Kirkman
Script Editor: Dave Andrzejewski
Production Assistant: Chris Davis

Special thanks to Hive13 (https://www.Hive13.org/) for use of their HackRF Blue SDR

Music:
"Sunset n Beachz" performed by Ofshane
"American Idle" by RKVC

©2024 Broadcast Blueprint LLC

0:00 Introduction
0:40 Wave Properties and Modulation
1:16 Early Broadcasting and AM
2:37 Edwin Howard Armstrong vs. Carson and Others on FM
6:01 Armstrong's Wideband FM System
7:25 Armstrong Drops the Mic
8:49 Quirks of FM
11:04 W2XMN, the First FM Station
12:03 The Guitar String Analogy
12:54 FM Demo Setup
14:01 An Unmodulated FM Carrier
15:03 FM in Slow Motion - Modulated at 1 Hz
16:06 Tracing Music on the Waterfall
16:27 Modulation Index and Audio Processors
18:29 Multiplex (MPX) Operation
20:35 MPX Demonstration and the Pilot Tone
21:14 Stereophonic Sound and Vinyl Records
24:12 FM Stereo Overview
24:56 AM Components of FM Signals
29:10 The Algebra Behind FM Stereo
30:40 Using Carson's Math to Improve FM
31:26 Pre-emphasis and De-emphasis
32:28 Empire of the Air: The Men who Made Radio
33:17 Conclusion