Crystal Radios: No Batteries? No Problem!

(To those who swear I've covered this topic before: I have; I just wasn't satisfied with my original video)

Remarkably simple and requiring no power source, crystal radios were the primary means of listening to commercial radio broadcasts until the late 1920s and early 1930s, when they were largely superseded by more sensitive tube-based heterodyne and regenerative receivers. However, they continue to be built by hobbyists and are a popular project for teaching children the basics of radio technology.

0:00 Introduction
0:52 Spark Gap Transmitters
2:02 Coherer Receivers
3:05 Magnetic Hysteresis Detectors
4:38 Reginald Fessenden and the Dawn of AM Broadcasting
5:06 Parallel Tuned Circuits /LC Resonators
6:29 Rectifying/Envelope Detectors
7:23 Hot-Wire Barretter
8:19 Electrolytic Detector
9:18 Early Crystal Detectors
9:50 Crystal Radio Basics
12:17 Cat's Whisker Detectors
12:56 P/N and Metal-Semiconductor Junction Diodes
14:39 Later Crystal Detectors and Diodes
16:26 1923 Ariel Crystal Set
17:11 Self-powered Crystal Radios
17:50 Crystal Radio Optimization and Range
20:52 Foxhole Radios
22:27 Obsolescence of Crystal Radios
23:05 1950s Miniman Rocket Radio
24:18 Outro

SOURCES:

[Woffy.]

As a lad during a very hot summer I visited my younger cousin Adrian, I showed him how to build a Crystal set from scrap wire etc. He told me just before his death that he was so fascinated by this magical thing we had built that he went on to study Radio, I only just found out his job was designing receivers for military satellites. Great channel, old school just the way we like it. I wish you were my teacher.

[darrylday]

Built one at the age of 10 from a library book. My dad had all the parts in little glass jars hanging from the ceiling. 40 years later I found myself teaching basic AC electricity to aircraft maintenance apprentices. I am grateful.

[DavidFerree]

My older brother got a little crystal radio for Christmas when he was about 10 years old. It was in a little red rocket ship looking thing. He eventually took it apart and hooked up an antenna to it and was receiving AM signals from all over the country. Years later when he was 14 and I was 13 he had progressed in his electronics tinkering to the point that he used that same little crystal radio as the guts of a broadcast station in our room with a horizontal wire antenna on top of our house. We had a radio show every evening, with me playing records (single 45s) and talking. The kids at school the next day always gave me reviews on our shows. Later still he did things like going through a local computer manufacturer's dumpster to retrieve mistakes they had thrown away and building super computers out of the parts. He joined the Air Force at 17 and his job was repairing guided missile systems. All from getting a toy for Christmas.

[paulmaxwell]

I received a cheap crystal radio kit for Christmas in about 1966. I had to wind the coil, assemble the parts etc. It didn't work. My grandfather, an aviation radio technician, came over, found the problem and replaced the 1N34 germanium diode. Presto! It worked! I thought he a was a genius. I spent many, many nights listening to radio stations thousands of miles away when I should have been sleeping.

[RambozoClown]

Great video. As a kid I read about trench or foxhole radios, and was amazed when I built one and it worked. Razor blade, pencil lead, coil wound on a toilet paper core, the whole shebang. I even surprised my dad.

[krdr]

Discovering the 1N34 Germanium diode at Radio Shack was the greatest thing in my young life. Crystal radio was so much easier without the cat whisker and potted diode.

[blueeyeswhitedragon]

I won the "Rocket Crystal Radio" in a newspaper contest and loved the way it picked up our local AM radio station and played music, battery free, while Imwas in bed getting ready to go to sleep.
The good old days.

[shmehfleh]

My grandmother lived in a relatively small rural community in Illinois, about 30 miles away from St. Louis. Her farm, as well as the rest of the town received its electricity from a diesel generator located in the nearby firehouse. It was only run for a few hours each day, during which everyone ran their washing machines, vacuumed, listened to their radios, or did whatever else required electricity before it was shut off again. I don't think her community was tied to an official 24/7 energized grid until after WWII, and my grandfather, who was a lineman for most of his career, helped do it.

[rodchallis]

It's like the Crystal Radio is The Spirit of Radio.

[carlosanvito]

It was the early 1960s. My grade school teacher gave us an assignment to pick up a book at the bookmobile and write a report. None of the books interested me, except for a book by Alfred Morgan, called the Boy's First Book of Radio and Electronics. I was instantly hooked. I built one of the crystal radios and was fascinated that I could actually do that. Fast forward, that interest resulted in me studying electrical engineering in the early 70s which led to a fabulous career. All that, thanks to the humble crystal radio. Too bad kids don't do things like that anymore.

[Ed_Stuckey]

I built my first crystal set at about seven years of age. That was ~1950. It was like magic. I've been interested in all things electrical and electronic since.

[Albertkallal]

I had many crystal radios as a child - several from Radio Shack. But, out of of all the ones I ever used?
That rocket radio blew them all away!!! - don't know why, but wow oh wow - they work beyond
And they were dirt cheap - available at the downtown Army and Navy store.

I used take my to school, and just clip the alligator clip to the school chain link fence, and it worked rather well.
(Grandin School)

At home?
Just clipped to the heater vent by my bed - listened to CFRN and Irv Shore in the morning. And to not be puny? That CFRN signal was crystal clear.

Very cool, and no batteries. Loved that Rocket radio as a child - and it worked really well.

[Evergreen]

I hear your "Spirit of Radio" sir. Longtime RUSH fan here. Great video!

[shawn.the.alien]

When I was in Junior High back in the '90s, I had a teacher (Mr. Dollar) who did an exploratory class on radio, and something we got to do was build crystal radios from kits. It taught me a lot about the basics of radio. I have two nephews that, when they get old enough, I'm gonna find some kits and teach them what I learned

[timd]

In 1958, I was 7 years old. My brother-in-law's step-father had a small plastic box with a wire coming out of it with an alligator clip on the end. Also had another wire with an earphone coming out of the other side. He let me listen to it. He opened the back of the plastic box and there was hardly anything in it. Fascinated me! We had a radio at home but it had to be plugged into the wall and turned in different directions to pick up various stations. I wasn't allowed to touch that radio. The crystal set had only one dial, 1-10, and turning it slowly would change the stations. I credit Mr W for getting me interested in electronics, building Heathkits in high school, electronics in the service and then a career with 2 electronics companies. Retired now!

[DJapan]

I had a Radio Shack kit as a kid to make one. That's how I learned that a microphone and speaker are the same thing.

[eyerollthereforeiam]

I love your opening gags, but THAT ONE IS THE BEST!!!

[jp-umfr]

England. What an excellent video. I built and did terrible things to crystal radios, some of which actually worked. With a roughly 200 ft aerial at 30 ft, I could even use an old extension loudspeaker. I learned more about the history of crystal radios, etc. watching your videos, than all the books I ever read. Well done that man, I'll put you up for a knighthood (but don't hold your breath).

[chrisgraham]

I built my first crystal radio at 9 years old in 1962 as a project in Boy Scouts. Even then, I was amazed at the technology that performed without batteries or plugged into a wall receptacle. Stringing an antenna wire across the length of my bedroom ceiling and hooking the ground clamp to the hot water radiator, I was tuned into the local rock-n-roll AM station, listening through a single piezo earpiece. My mother, who came from London, England, remembered well her family's first crystal radio that required manipulation of the "cat's whisker" to maintain a broadcast signal. Knowledge of crystal radio technology will be valuable information to have after the zombie apocalypse.

[frankschuler]

Funny story. I built a crystal radio for a science fair project as a kid in the 80's...got a blue ribbon! I still remember being fascinated by the ability to build a radio with just a few components and some blocks covered with aluminum foil (you'd slide the blocks over one another to act as a variable capacitor). I still remember Dad having to visit multiple Radio Shack locations to find the right components. I wish I still had it. It was little more than a handful of wire stuck to a block of wood using thumbtacks to complete the junctions.