I. RADIOHISTORY

II. What is radio?

A. Sending sound through the air by piggybacking it on to electrical noise

III. Electricity

A. Known for thousands of years

1. Lightning (the gods being pissed off)

2. Bagdad battery

a) 250 BCE

b) Plate medallions?

c) Shock worshippers to show the power of the gods

B. 18^th Century

1. Ben Franklin

a) Flew kite in thunderstorm

b) Proved lightning is electricity

2. Other people used electricity as a toy

a) Generated static electricity

(1) Rubbed cat skins on glass or amber rods

(2) Spun sulfur balls

b) Zapped everything and everyone in sight

3. Luigi Galvani

a) 1786 – experimented to show that electricity was in muscles

(1) Called it “animal magnetism”

(2) Touched different metal rods to frogs’ legs which twitched

4. Alessandro Volta

a) Thought Galvani had got it backwards

(1) It was the different metal rods, not the frogs’ muscles, that caused the electrical impulse

b) Created his pile

(1) Stacked up alternating zinc and copper disks

(2) Added a mild acid solution

(3) Created an electrical current

(4) Proved electricity could be created chemically

(5) The world’s first workable battery

(a) Greatly improved electrical research

(b) No more depending on static electricity

C. 19^th Century

1. Hans Christian Oersted

a) Didn’t believe electricity and magnetism were linked

b) 1820 experiment

(1) Put a compass needle near an electrical circuit

(2) The needle swung when the circuit was turned on

(3) Proved electricity and magnetism were linked

c) Kind of blew his point

2. William Sturgeon

a) Created first electromagnet in 1825

(1) Wrapped a wire around a soft iron bar

(2) Ran electricity through the wire

(3) The bar attracted metal – 9 ounce bar lifted 7 pounds

3. Michael Faraday

a) Reversed Sturgeon’s process

b) Faraday’s experiment in 1826

(1) Ran a magnet through a wire coil

(2) Produced electricity

4. Samuel Morse

a) Combined Sturgeon and Faraday’s ideas

b) Invented the telegraph

(1) Pressing a key that created an electrical connection

(2) The electrical impulse sent down a wire

(3) The impulse triggers an electromagnet which clicks for the length of the impulse

(4) Alter the length and pattern of the impulse creating a code

c) Using the telegraph required

(1) Skill

(2) Learning a foreign language – the Morse code

(3) Not good for the average person

(a) Fast, yes

(b) Easy, no

(c) Something needed to be done

5. A detour into sound

a) Johannes Mueller – 1840

(1) Researched physical senses to see if they were separate or the same

(2) Each sense detected different things

b) Herman Hemholtz – 1857

(1) Mueller’s pupil

(2) Researched sound

(a) Discovered sound produced vibration

(b) Different vibrations had different frequencies

(i) Sound travelled at different frequencies

(ii) Used an electromagnet to attract arms of a tuning fork

(a) The arms vibrated

(b) The arms produced sound

c) Leon Scott de Martinville

(1) Also researched sound

(2) Approach was visual

(a) De Martinville’s experiment

(i) Attrached a bristle on the end of a stick

(ii) Attached stick to a membrane

(iii) Put membrane on the end of a cone

(iv) Placed end of bristle against a piece of smoked glass

(v) Spoke into cone

(a) Membrane vibrated

(b) Bristle rubbed against the smoked glass

(d) Different sound etched different patterns

(e) Patterns were always the same for the same word

(f) Painted pictures of sounds

6. Summary so far

a) Electrical impulses can be send down a wire

b) Electrical impulses can cause an electromagnet to open and close

c) Each sense detects different things

d) Sound are different things that cause vibrations

(1) that propagate at different frequencies

(2) no two frequencies alike

(3) the vibrations can be seen using de Martinville’s setup

(4) an electromagnet can make metal vibrate at different frequencies

7. the telephone

a) invented by Alexander Graham Bell and Elisha Gray

b) combine all the ideas

(1) de Martinville’s cone with a membrane at the small end

(a) cover the membrane with a thin sheet of iron

(b) vibrate the membrance to sounds

(2) Faraday’s electromagnet

(a) Membrane vibrates in an electrical field

(b) Creates different frequencies of electrical impulses

(3) Impulses sent down Morse’s wire

(4) Sturgeon’s electromagnet

(a) Causes an iron-covered membrane in de Martinville’s setup to vibrate

(b) Creates sound like Hemholtz showed

(5) Reverse the entire process

D. Radio is telephone without wires

E. Heinrich Hertz

1. Hemholtz’s student

2. Played with electricity instead of sound

a) Tried to see if electricity traveled in the air in frequencies the way sound did

b) Build a spark gap generator

(1) Created an electrical current

(2) Had a gap the electricity had to jump, creating a spark

c) Build a receiver to pick up the spark

d) When the generator created a spark, the receiver also sparked

(1) The receiver’s spark depended on distance

(a) Strongest at specific distances

(b) Demonstrated electricity propagated through air at specific frequencies like sound did

F. Guiglielmo Marconi

1. Took all the ideas developed over the last hundred years and combined them

2. Added an aerial (an antenna) to extend the distance

3. Boosted the power by adding a step-up transformer

4. Using Morse’s telegraph key and code he could send electrical impulses and thus messages through the air for great distances

5. This is radio

a) Actually a wireless telegraph

b) Still required skill and learning a foreign language

G. Nicola Tesla

1. Invented the Tesla coil

a) First amplifier

b) Raised electrical current high enough that the air could conduct the entire current

c) Marconi’s radio only had the power the send the spikes in impulse

2. His work was the key to wireless sound radio

H. Reginald Fessenden

1. Variation in electrical amplitude created by a voice like a telephone

2. Radio waves should be able to do the same thing

3. 1900 – first radio voice transmission

a) Short range (about 15 miles

b) Lousy quality

c) Needed a lot more power

I. Ernst Alexanderson

1. Invented a new electrical generator, the Alexanderson Alternator

a) Boosted the power to 100,000 hertz

b) December 1906 Fessenden did the first radio broadcast

(1) Poetry

(2) Bible readings

(3) A woman singing opera

(4) Violin playing Christmas carols

(5) Could be picked up hundreds of miles away

(6) Range still limited, sound still not all that good

(7) Needed more power

J. Lee De Forest

1. Call the “Father of Radio”

a) Not true

b) He was a tinkerer

(1) Would take various parts, , put them together, and see what happened

2. The audion tube

a) De Forest took an English invention, the Fleming valve (what we would call a vacuum tube)

b) He added a piece of bent metal to the tube

(1) Greatly increased the power of the tube

(2) Amplified the radio signal the way Alexanderson’s generator amplified electrical power

c) De Forest had no idea how the audion tube worked

K. Edward Howard Armstrong

1. True father of radio

2. Understood how the audion tube worked

3. Improved the audion tube

a) Developed what he called “regeneration”

b) Fed the signal back into the tube up to 20,000 times per second

(1) Increased the power of the tube

(2) Became and amplifier that increased range and quality of radio transmitters

(a) Fessenden invented ability to broadcast sound

(b) Armstrong invented ability to broadcast good sound

4. Armstrong then invented a good receiver

a) The superheterodyne

(1) Combined high frequency waves with low frequency waves

(2) Fed the waves back into the system

(a) Amplified the signal

(b) Increased the sensitivity

(3) The first true home, and portable, radio

L. The business of radio

1. Was a toy for most people who built their own crystal radio sets

2. David Sarnoff

a) Major figure in radio

b) Worked for American Marconi Company

c) Knew wireless telegraphy was a point to point medium like the telephone

(1) One message

(2) One recipient

d) Knew that, although the message was intended for one person, it could be picked up by anyone listening

e) Thought radio should broadcast to everyone on purpose instead of by accident

f) 1916 – the “Radio Music Box Memo” outlined his idea

(1) Make radio a mass medium

(2) Put a “Radio Music Box” in every home

(3) Broadcast programming that the “Box” could receive

g) World War I ended the idea of public radio

(1) All radios were taken by the military

(2) Research in public radio was suspended

(3) Started up again after World War I

h) Radio Corporation of America (RCA)

(1) Four American radio manufacturers formed a single company to share in all radio-related patents

(a) American Marconi

(b) General Electric

(c) American Telephone & Telegraph

(d) Westinghouse

(2) Sarnoff named and commercial manager

(3) Used Armstrong’s patents to manufacture transmitting and receiving equipment