- Frequency modulation or FM radio
changed the way we communicate.
It was according to Howard Armstrong's
eventual nemesis David Sarnoff, "A revolution".
I've seen books and videos and articles about this history
but they always skim over the science.
This is my attempt to tell an accurate
but clear and simple description
of how Howard Armstrong invented FM radio in the first place
and how it was so amazing that it led to his destruction.
Ready? Let's go.
♪ Electricity ♪
- In 1923, Howard Armstrong worked with his friend,
David Sarnoff, then the vice president of RCA
to make the Radiola radio
and soon Armstrong and Sarnoff made millions of dollars
and broadcast radio took over the culture.
There was only one problem, static,
and it had to do with the nature of AM radio.
Let's start with some basics.
Radio waves aren't sound waves.
I know crazy, right?
They're actually invisible light waves.
Radio waves are used as the medium
that is used to transmit or carry the sound information.
In AM radio sound is converted into an electrical signal
and that signal is used to change the height
or the amplitude of the wave.
Thus the name AM radio for amplitude modulation.
However, every time there is a spark, it makes a radio wave
which increases the amplitude of the wave
which creates static in AM radio.
(upbeat music)
(static)
Sarnoff had repeatedly said that he wished
he had a little black box to get rid of static
and Howard Armstrong thought he had the solution.
Why not create a radio wave
where the amount the frequency deviated from the original
more squished or stretched, corresponded
to the sound wave produced in the microphone
instead of changing the height.
For this reason it is called FM radio
for frequency modulation.
Actually many scientists were interested
in using frequency modulation
in the late teens and early twenties.
However, in 1922, John Carson,
the head mathematical theoretician at Bell Laboratories
wrote a paper that it wouldn't work.
Well to be more accurate, he said it would work,
but it inherently distorts
without any compensating advantages whatsoever.
Carson eventually concluded that quote
"Static, like the poor will always be with us."
Now, Armstrong was even more determined
saying, quote "I could never accept findings
based almost exclusively on mathematics."
In 1928 Howard Armstrong decided to spend all of his time
trying to make FM radio.
For three years, he got nowhere.
Then he had a radical idea.
He knew that in order to make FM radio,
you by necessity had to change the frequency.
He also knew that with the technology available at the time
he needed to keep that fluctuation to a minimum
or it distorted the signal, as Carson mathematically proved.
But then it was impossible to have the full range
of sound and to reduce static.
What if, he thought, you started with a low frequency
with small changes and then multiplied it
to a higher frequency with large changes
and made the receiver only receptive to large changes.
This is called broadband FM radio
and it was not an easy task
and it took him till 1933 for him to get it right.
But when he did it worked even better than he had hoped.
The static was gone.
(static)
(upbeat music)
You could transmit the whole range of human hearing
instead of a small range like AM.
You could even transmit two signals
at the same time to make surround sound.
And Sarnoff hated it.
You might ask how can a signal from a microphone
be changed into variations of the frequency of the wave?
Well, it's a little confusing
but Armstrong started with creating an AM signal
on a very low frequency radio wave.
He then suppressed the original smooth radio wave
and re-installed it, 90 degrees out of phase.
This creates a PM or phase modulation.
So instead of the signal changing the height of the wave,
it changes the phase of the wave or where the wave stuck.
He then used a capacitor to smooth out
or integrate the system and make it into an FM signal.
Finally, he used harmonics to multiply the signal
to get to the carrier frequency
and frequency variations that he wanted.
How about the receiver?
Well, to talk about an FM receiver
let's start with how Armstrong's AM receiver worked first.
With AM, Armstrong amplified the signal from an antenna
and then mixed it with another signal
to create a lower intermediate signal
that was easier to deal with.
He then filtered it to his desired frequency,
amplified that signal and then used electronics
to detect the changes in amplitude.
By the way, this envelope detector
could be as simple as a one-way valve.
Finally, he amplified the sound
and projected it onto a loudspeaker.
The FM receiver was only slightly different
than the AM receiver.
First with FM, you don't want a narrow frequency filter
or you cut out all your information.
So he used a broad frequency filter.
Second, he used something he called a limiter,
because it limited the height of the wave.
Basically it saturated the system so that any variation
in the height of the waves was cut off.
Since the real signal was in the variation of the frequency
and the variation in the height
was only due to static anyway.
Third, instead of an envelope detector Armstrong
used something he called a discriminator
that would, as Armstrong put it, quote,
"Translate variations in frequency
into variations in amplitude."
Armstrong created two tune circuits
with coils and capacitor.
One tuned to above the carrier frequency
and one tuned to below the carrier frequency.
If a wave was created with no modulation
that would work equally badly in both circuits.
Then the two coils labeled 48 and 49
would get the same voltage induced in them
which would cause no current to flow between them.
However, if the frequency was modulated higher or lower
then one circuit would resonate better
and at a higher amplitude
and the other would resonate worse with a lower amplitude.
This would cause one coil to have higher voltage
induced than the other coil,
which would create a current between them
and correspondingly current in the speaker or headphones.
The bigger the frequency difference,
the bigger the amplitude of the current in the headphones.
In this way Armstrong converted changes in frequency
to changes in amplitude in the speaker.
Whew. So if FM was so much better than AM
why wasn't Sarnoff happy?
Well Sarnoff was hoping for something to improve his system
not something to supplant his system.
What to do?
Sarnoff decided to crush his friend's new invention.
Kicked Armstrong out of his laboratory
in the Empire State Building, had his scientists
write articles denigrating FM,
and forbade RCA from using FM radio.
Undeterred Armstrong sold all his stock in RCA
and started his own FM company called the Yankee Network.
It wasn't until five years later
the Sarnoff realized his mistake
and tried to get Armstrong to sign a million dollars worth
of a non exclusionary license.
Armstrong told Sarnoff to get lost.
Armstrong's lawyer thought his client was crazy.
Quote, "That's the first time I ever heard of an inventor
turning down a million for a non exclusionary license."
Sarnoff was incensed.
He started a personal war with his former friend
and used his influence to have the FCC
change the radio frequencies available for FM,
making Armstrong's equipment and company worthless.
Sarnoff and RCA then started using FM without permission
and soon many other companies followed suit.
In July of 1948, Armstrong sued.
RCA decided to win by making the lawsuit
as long and arduous as possible.
Or as Armstrong said, quote,
"They will stall this thing until I'm dead or broke."
And this lawsuit dragged on and on.
Armstrong's deposition lasted a full year.
In 1952 he ran out of money
and had to have loans to pay his lawyers.
On February 20th, 1953, Sarnoff lied under oath
that quote "RCA has done more to develop FM
than anyone in this country, including Armstrong".
Defeated, Armstrong tried to settle,
but Sarnoff wouldn't let him.
In November of 1953, Armstrong admitted
the state of his finances to his wife, Marion.
They had a horrible fight
and Armstrong hit her arm with a poker.
Marion fled the house never to see her husband again.
On January 31st, 1954, exactly 40 years
after Armstrong stayed up all night
with Sarnoff demonstrating his regenerative circuit.
A date they celebrated for decades.
Armstrong wrote his wife an apology,
removed the air conditioner from his apartment window
and jumped 13 floors to his death.
He was 63 years old.
When David Sarnoff heard of Armstrong's suicide
he blurted "I didn't kill Armstrong."
But he must have known he had a hand in Armstrong's
desperate act and wept openly at his funeral.
Marion Armstrong continued all of her husband's lawsuits.
Eventually she would file 21 patent lawsuits
and win all of them.
She won over $10 million in damages over the next 11 years.
Let's go back to 1934 for a bit.
Part of the reason that David Sarnoff
did not want to supplant his system with FM
is because he was cash poor
because he had already poured $5 million
into controlling a strange item called a cathode ray tube.
This is why Sarnoff and RCA eventually became
the titans of CRT television.
But what is the cathode ray tube?
Why was it invented?
And what's its connection, to not only television
but also the oscilloscope, radar,
x-ray machines, the discovery of the electron
and the photo electric effect.
Well, that starts next time
on The Secret History of Electricity.
♪ Electricity ♪
- Thanks for watching my video.
That was my last video on the history and physics of radio.
Now I'm going to move on to the cathode ray tube,
X-rays, discovery of electrons, even quantum mechanics,
but don't worry I will eventually get
to the discovery of television 'cause that's a crazy story.
So why don't you subscribe?
And then you will know all my new videos.
Okay. Have a nice day.