Samuel Gompers Vocational & Technical H.S.455 Southern Boulevard, Bronx, New York 10455-4966
Telephone (718) 665-0950 Fax (718) 292-3164Principal: MaryAnn Hawthorne
Assistant Principal of Electronics: Robert Cole
CRYSTAL RADIO
PROJECT
Summer 2002
The Crystal Radio ProjectIntroductionThis summer you will have wonderful opportunity to explore the world of communications through the study of the crystal radio. This project consists of a series of self-guided activities. However, it is strongly encouraged that students work with other students, family members and even consult with local experts such as educators, hobbyists, and even amateur radio builders and operators. Hopefully, you will find additional areas of interest and experimentation. Feel free to explore and learn this summer, all of your experiences will help you prepare for your next year of study at Samuel Gompers High School.
What is needed to for this project?In order to complete all aspects of the project the following items will be needed:
Library books that address Physical Science or Physics or Basic ElectronicsA Crystal Radio KitComputer Internet AccessA Working Home RadioA Composition Notebook to keep permanent records
Is it necessary to complete everything in this project?The goal of this project is to provide students with many different opportunities to learn about all aspects of the radio. However, not all students will have access to all of the necessary items, or choose to purchase a crystal radio kit. While, some students may not find or have access to library books that contain “all of the requested information”. Therefore, it is suggested that students complete as much as possible “within reason” for the time they have available to work on the project. You get as much out of the project as you put into it.
Should the project be completed in order?It is not necessary that the project be completed in the sequence in which it is presented. It is important to locate your crystal radio kit as soon as possible so that you will have it when you are ready to begin its construction. Remember, if you need to order it on-line there is shipping time! It is strongly suggested that the parent and student read through the project and make a “flexible time-line” for how they plan on completing the project or parts of the project
How should information be kept for this project?Student may write on the project sheets using the boxes provided. However, additional space may be needed to fully complete a response. To complete a response, the back of the project paper may be used. If additional space is still needed a separate sheet of paper can be stapled onto the original lab paper. If a student chooses to conduct additional experimentation or investigate additional concepts or questions, this information should be kept in a (black and white) composition notebook in which the pages are permanent. References for all sources should also be kept in the composition notebook (see reference section). Photocopies of all resources should be in a separate two-pocket folder. You may make as many additional copies of any pages you need to record additional information or investigations. Copied pages can be inserted into the project package in the appropriate locations.
What safety considerations should be observed for this project?Only purchase crystal radio kits that do NOT require soldering.When experimenting with the crystal radio antenna/ground, do not put the wire into an electric outlet or devise.Do not open the back of your home radio, only observe the external parts.
Good Luck and Have Fun!
SECTION I
The Radio inYour Life
Alphabet Squares: RadioYour Favorite Radio Stations
AM Radio StationsFM Radio Stations
Parts of Your Home RadioListening to Old-Time Radio Programs
Alphabet Squares: RadioDirections: Think any of as many words as you can that are related in any way to the word “radio”. Write each word in the box that has the same letter that the word begins with.
A-B C-D E-F G-H
I-J K-L M-N O-P
Q-R S-T U-V-W X-Y-Z
Your Favorite Radio StationDirections: Fill in the table below with information about your favorite radio station.Station Name (4 letters) Circle One: AM or FM
Station Call Numbers
Type of Programming(music, talk, etc.)
Disc Jockey Name(s)
This is my favorite station because…
I like to listen to my favorite radio station when …
The best story I ever heard on my favorite radio station was …
The one thing I would change about my favorite radio station is …
AM Radio StationsDirections: Turn on your radio and put the AM/FM selector on AM. Set the radio to the lowest value on the AM scale. Then using the tuner, slowly move up the AM scale until a station is heard. Listen to the station for few minutes so you may record the requested station information. Then using the tuner, continue to move up the AM scale until the next AM station is heard; and record the requested station information. Try to locate as many AM stations as you can!
Station Name(4 letters)
Station Call Numbers
Programming Description
Area of Broadcast(ie. NYC, NY)
Signal strength(good or poor)
FM Radio StationsDirections: Turn on your radio and put the AM/FM selector on FM. Set the radio to the lowest value on the FM scale. Then using the tuner, slowly move up the FM scale until a station is heard. Listen to the station for few minutes so you may record the requested station information. Then using the tuner, continue to move up the FM scale until the next FM station is heard; and record the requested station information. Try to locate as many FM stations as you can!
Station Name(4 letters)
Station Call Numbers
Programming Description
Area of Broadcast(ie. NYC, NY)
Signal strength(good or poor)
Parts of Your Home RadioDirections: Select a radio in your home and fill in the table below with regards to its external (outside) parts. If you do not know the exact name of a radio part, you should record the “common name” in the table. Do not open your radio, as you may damage your radio or hurt yourself!
Part Name(actual or “common”)
Description of Part Function of Part How Part is Used(if applicable)
Listening to Old-Time Radio ProgramsDirections: Old-time radio programs can occasionally be heard on specific radio stations during limited times. However, old-time radio shows can be heard on-line at any time. One popular site for on-line old-time radio is Radio Spirits (http://www.radiospirits.com). Radio Spirits has a daily featured old-time program and has many previously featured show available for listening. Select and listen to a show, then fill in the requested show information in the table below.Show Name
Episode Name
Names of Actors
Original Date of Broadcast
Commercials/Sponsor(s)
Episode Plot
Historical Information Referred to During Broadcast
Why did you pick this show?
Why did you like or dislike the show?
SECTION II
Exploring The Crystal Radio
Obtaining and Constructing a Crystal RadioExperimenting with the Antenna & Ground on your Crystal Radio
A Radio Log: Radio ReceptionThe Four Basic Parts of the Crystal Radio
The Circuit Diagram of the Crystal Radio Detectors
Obtaining & Constructing a Crystal Radio KitOne of the best ways to learn how the radio works is to actually build a radio. The simplest kind of radio to build is the crystal radio. In fact during World War II soldiers constructed “foxhole radios” using the lead from a pencil, a razor blade, and a coil. While, beginning radio enthusiasts have built The Quaker Oats Box Radio Set which requires only the following:
Quaker Oats Box Set Materials(75 ft.) Antenna wire (100 ft.) Plastic coated Hookup wire #24 (1) Quaker Oatmeal box, empty(1) germanium diode (1N34)(1) capacitor (0.001 microfarad, any voltage)(1) resistor (47,000 ohm)(1) ear plug, high impedance Solder
(http://www.nightscience.com/project.html)
However, it is not recommended that the beginner attempt to build the Quaker Oats Box Set until you learn to solder in a properly supervised environment.
There are several brands of complete kits (Minilabs Science: Crystal Radio and Transtronics: Technokit Crystal Radio) available that will allow you to safely build a crystal radio without soldering. However, it is highly recommended that you select a kit that allows you to wind your own coil and uses an earphone not a speaker for the audio output.
Finding a Crystal Radio Kit in the Retail StoresCrystal radio kits can be commonly found in electronics stores, hobby stores, and science section of many large toy stores. Remember, it is best to try to find your crystal radio kit in a local store so that you do not have to pay shipping and handling charges. A typical kit cost about eight to twelve dollars.
Radio Shack (http://www.radioshack.com) Toys ‘R UsK-B Toys
Ordering a Crystal Radio Kit On-LineIf you cannot find a crystal radio kit in a local radio store they can be found on-line. However, you will have to pay shipping and handling charges (generally around five dollars additional). You may search for an on-line seller, or use one of the sites below..
Science Kits (http://www.sciencekits.com)American Science & Surplus (http://www.sciplus.com)Science City (http://www.science-city.com)Amazon (http://www.amazon.com)
Experimenting with the Antenna & Ground on your Crystal RadioIt is critical that you carefully follow the directions for the assembly of your crystal radio. However, even if you have correctly assembled your radio, you may not be able to hear any AM radio broadcasts. Your crystal radio will only work if you have both a “good antenna and ground”.
Directions: Try the following antenna and ground set-ups, make-up your own and record the results in the table below:
Not attached – extend wire straight outSet OneAntenna wire not attachedGround wire not attachedAntenna wire to cold water faucetGround wire not attachedAntenna wire not attachedGround wire to cold water faucetAntenna wire to cold water faucetGround wire to hot water faucet
Set TwoAntenna wire to metal window frameGround wire not attachedAntenna wire not attachedGround wire to metal window frameAntenna wire to metal window frameGround wire to metal window frameAntenna wire to metal window frameGround wire to radiator pipe or faucet
Set Three: Make up your ownAntenna wireGround wireAntenna wireGround wireAntenna wire Ground wire Antenna wire Ground wire
Set Four: Make up your ownAntenna wire Ground wire Antenna wire Ground wire Antenna wire Ground wire Antenna wire Ground wire
A Radio Log: Radio ReceptionDirections: Using the prompts, write an appropriate response.A “good antenna” is …
The ground improved reception when …
My radio reception was best when …
The stations I heard on my radio were …
Radio reception at night time was …
Draw a diagram of the wire coil showing where the reception for different stations occurs.
The Four Basic Parts of the Crystal RadioDirections: Research the crystal radio and fill in the table below.
Coil Variable Capacitor Crystal Diode EarphonesDescription of Crystal Radio Part
Function of Crystal Radio Part in the Radio
Construction and/or Use of the Crystal Radio Part
Possible Modification of Crystal Radio Part
The Circuit Diagram of the Crystal RadioDirections: Research the electronic schematics and fill in the table below.
Radio Part Symbol FunctionAntenna
Ground
Coil
Tuning Ball
Earphone
Diode
Using the symbols above draw a Circuit Diagram for a Crystal Radio
Radio DetectorsIn radio terminology, a detector is a substance or devise that allows electrical current to move in only one direction. The crystal radio derives its name from the fact it originally used “metallic crystals”” as part of its detectors. One of the earliest and better crystal detectors was produced from a substance called galena. Galena is a mineral composed of lead and sulfur. If a very thin metal wire (“cat’s whisker”) is gently touched and held on a piece of galena a very effective and sensitive detector can be produced. However, today substances such as silicon and germanium are now more commonly used as detectors. Both, silicon and germanium, have crystal structures that easily allow them to selectively pass electrical current in one direction. And if impurities such as arsenic or gallium or added their conductivity can be significantly increased. Hence, the crystal radio you bought probably has a germanium diode and not “metallic crystals” of galena connected to a cat’s whisker!
Directions: Research basic electronics and fill in the table below.What is a vacuum tube, use an illustration to support your written description?
What is a diode?
How does a vacuum tube work?
What are some important applications of vacuum tubes in electronics?
What are semiconductors and solid-state devices, and give examples?
What advantages do solid-state devices have compared to devices with vacuum tubes?
SECTION III
Understanding Radio Waves
Understanding WavesThe Electromagnetic Spectrum
Amplitude and Frequency ModulationUnderstanding Resonance
UNDERSTANDING WAVESAny disturbance that transfers energy through matter or space is called a wave. A substance or region through which a wave is transmitted is called a medium. There are two types of waves, transverse and longitudinal. Directions: Research Waves (light and sound) and fill in the table below.
Transverse Waves Longitudinal WavesDefinition
Examples
Example(s) of a Medium for a Wave
Speed of Wave
Characteristics of WavesAmplitude Wavelength Frequency
Definition
Unit of Measure
Symbol
Draw a diagram of a wave that labels the Amplitude (including: Crest and Trough) and Wavelength
The Electromagnetic Spectrum
Directions: Consult a book on Physical Science or Physics and complete the tables below.Radio Waves Infrared
RaysVisible Light Ultraviolet
RaysX-rays Gamma
RaysWavelength
Frequency
Uses
Specific Radio WavesType of Radio Wave Frequency Wavelength
Amplitude and Frequency ModulationWhen transmitting radio waves two characteristics can be varied, amplitude and frequency. The variation of either amplitude or frequency is called modulation. Therefore, AM stands for amplitude modulation and FM stands for frequency modulation.Directions: Consult a book on Physical Science or Physics and complete the table below.Define Amplitude.
Describe how amplitude can be varied.
Draw a diagram illustrating amplitude modulation.
Define Frequency.
Describe how frequency can be varied.
Draw a diagram illustrating frequency modulation.
UNDERSTANDING RESONANCERadio waves are electromagnetic waves that are sent out at many different frequencies. When a radio wave reaches an antenna, some of the energy from the different radio waves is transferred to the antenna wire. The received signal then flows to the coil of wire. Since there are many different radio waves striking an antenna, many different signals are sent to the coil of wire. In order to select a specific station, or radio frequency, it is necessary to understand the concept of resonance.
Every object has its own frequency of vibration, or natural frequency. If one object is vibrating at the same natural frequency of a second object, the second object can absorb energy from the first object and will also begin to vibrate. The ability of an object to absorb energy of its own natural frequency is called resonance.
Interestingly, even an object such as a coil of wire has a frequency of vibration, or natural frequency. The charge that moves back and forth through the coil does so at a specific frequency, and this is the resonant frequency of the coil. To select a specific radio station, the resonant frequency of the wire coil must be the same frequency of the desired radio station. If the signal of the desired frequency is resonant to the wire coil it is “filtered to pass and will be detected” while other signals simply move into the ground. Crystal radios use a metal slider (tuner) which is moved along the bare wire of your wire coil so that you can match the resonant frequency of different size sections of your wire coil to the frequency of the different broadcast stations. In addition, to having a long antenna it is equally important that the antenna also be resonant to the desired broadcast station frequency. Directions: Consult a book on Physical Science or Physics and complete the tables below.Describe how you could demonstrate resonance with tuning forks?
Draw a labeled diagram of your tuning fork demonstration of resonance.
Draw a diagram that demonstrates how a radio can best select a single broadcast station
SECTION IV
Research and Thought Questions
&Reflections
Research &Thought QuestionsDirections: Select any of the questions below and write a response(s) in your composition notebook. Remember to record all references in the proper format. Feel free to modify or extend any question or create your own.
1. What is the advantage of AM radio waves compared to FM radio waves?
2.Why doesn’t the crystal radio need a power source?
3. How does the crystal radio differ a “regular radio”?
4. What is short-wave radio?
5. How can you improve the reception of a crystal radio?
6. How do transistor radios work?
7. How is a “foxhole” radio made, and how does it work?
8. Howdoes a speaker work, and how can it be connected to your crystal radio?
9. How would changing the diameter/length of the coil affect the reception of your crystal radio and why?
10. If the coil was wound around an iron (ferrite) rod instead of a hollow cardboard tube, how would this affect reception and why?
11. How does an antenna work, and how could you maximize the effectiveness of the antenna in the smallest amount of space?
12. What are some of the other minerals/substances that have been used as detectors, and how effective are they (compared to each other)?
13. Why do crystalline structures allow currents to pass through them in only one direction?
14. How do impurities increase conductivity in silicon?
15. How does a microphone work, and how is the sound converted into a radio wave?
16. How is radar used to determine the distance/speed of objects?
17. How are speakers designed to produce sound?
18. Who really owns the airwaves (public or private)?
19. How has government marginalized local radio stations?
20. How did FM radio evolve?
21. How did Pickard/Tesla/Marconi contribute to the development of the radio?
Reflections on The Crystal Radio Project
Directions:1. In your own words write a one-page summary of what you learned from this project. Be sure to include a discussion of the radio/radio-related topics that would feel comfortable presenting to your peers as well as topics that you feel you would like to revisit, and why? In addition, you should discuss interesting topics/ideas you encountered during the course of the project, and a description of topics you would like to continue researching, and why?
2. In your own words write a one to two page description of how you felt about the crystal radio project. In discussing your feelings you might address questions such as:
a. Was the project interesting and fun?
b. Which parts of the project did you enjoy the most/least?
c. How would you improve the project?
d. Which parts of the project were hardest/easiest?
e. If you had more time, how would you improve/extend your project?
f. How well did you work by yourself?
g. Did you get assistance from anyone, when, and how much?
h. How well did you understand what was expected of you from this project?
i. How well did you plan and organize your time?
j. How would you evaluate the work you completed on this project?
k. Did any ideas, opinions, or beliefs you had change because of something you learned while working on this project?
l. How would you get a younger sister/brother ready to start a project like this?
m. Was build the actual radio a worthwhile experience for you, and why?
n. How did working on this project impact on your summer vacation?
SECTION V
ReferencesHow to Write a Bibliography
Writing a Bibliography for a Computer Web SiteEvaluating a Computer Website Form
How to Write a BibliographyA bibliography is a list of books and other sources that have been used in your research. There are many different ways to write a bibliography, and this sheet uses the bibliographic format recommended by District 99 teachers, and is based on MLA style. There is a glossary of terms below that defines words that may be unfamiliar. The following tips may be of some assistance in writing your bibliography:
• The book or magazine title is always underlined in a bibliography!• If a citation is more than one line long, indent the second line five spaces.• Arrange the bibliography in alphabetical order, by the author’s last name. If there is no author listed, use the first word of the title (not “a,” “an,” or “the”).• When there is more than one author, list the authors in the order they are listed on the title page.• If you use information from an article in a book or magazine, the article is listed before the title.
Book Citations:Bibliographic citations for books vary. These examples can help you write your bibliography for many types of book citations.
Book with one author:Lavender, David. Snowbound: The Tragic Story of the Donner Party. New York: Holiday House, 1996.
The author is listed, last name first. The title is underlined. The city where the book is published is listed followed by a colon and the name of the publisher followed by a comma. The year the book is published is then listed followed by a period.
Book with two authors:Lurie, Jon and Jimmy Clarke. Fundamental Snowboarding. New York: Lerner, 1996.
A book that has an editor:Ehrlich, Amy, ed. When I was Your Age: Original Stories About Growing Up. Cambridge, Mass.: Candlewick Press, 1996.
If the city of publication is unfamiliar, the name of the state or country is listed as well.
A book without an author:Mobil Travel Guide, Southeast. New York: Fodor’s Travel Publication, 1997.
An article in a book without an author:“Fiji.” The World Fact Book. Central Intelligence Agency: Washington, 1997.
The title of the article is listed before the title of the book.
Encyclopedia and Other Reference Books:An encyclopedia article may or may not have an author. The author’s name can be found at the end of the article. An article that has an author is called a “signed article.”
Signed articles:Sutherland, Zena. “Literature for Children.” World Book Encyclopedia. Volume 12. Chicago: World Book, 1997.
The name of the encyclopedia article is placed after the author’s name and put in quotation marks.
Unsigned articles:“Motion.” Encyclopedia Americana. Volume 19. Danbury, Connecticut: Groliers, 1994.
Where to find the information:Information for bibliographies is taken right from the source. Look at the title page for the publisher, city, and author. Copyright information is found on the verso page.
Glossary:biography --- A book written about a person’s life.bibliography --- A list of materials used in creating a report or paper.citation --- Source of information used in a report.et al. --- “and others”periodical --- Publication, especially magazine or newspaper that is printed in regular intervals.place --- City where the publisher is located.publisher --- The company that produces the material.signed --- An article that has an author listed.verso --- Opposite of the title page (the left page of a book).
Writing a bibliography for a Computer Web Site
Bibliographies for CD-ROM and the World Wide Web:When using non-book materials, include the publication medium (CD-ROM or World Wide Web, etc.), the vendor’s and publisher’s names (if known), and the date of database publication.
“Maya Angelou.” UXL Biographies. Version 2.0. CD-ROM. Farmington Hills, MI: UXL, 1999.
“Belize.” UXL Worldmark. Version 1.0. CD-ROM. Farmington Hills, MI: UXL, 1997.
Burke, Ronald. “Vatican City.” World Book Multimedia Encyclopedia. CD-ROM. Chicago: World Book, Inc., 1999.
World Wide Web/Internet:
Ashmawy, Alaa. Seven Wonders of the Ancient World. 26 August 1997. <http://pharos.bu.edu/Egypt/Wonders>
Welcome to the White House. U.S. Government. 3 September 1999. <http://www.whitehouse.gov>
Evaluating a Computer WebsiteDirections: For each major website used in this project, you should complete an evaluation of the site using the form provided on the next page. You many photocopy the form, type it into your computer or write it by hand. Remember, each website evaluation should have an appropriate bibliography. Feel free to modify the form as necessary.
Evaluating a Computer Website FormDate of Web Site Visit: ______________________
Name of Web Site: ________________________________________________________________
URL Address: http://www. __________________________________________________________
Who Posted the Site: _______________________________________________________________
Purpose/Goal/Reason for Site: _______________________________________________________
Last Updated: _______________________ Grade Level(s): ___________________
Major Topics Addressed in Website:
Quality of Information provided for each topic:Poor: Insufficient for understanding of topicGood: Sufficient for understanding of topicExcellent: Thorough and comprehensive coverage of the topic
Topic Name Quality/Reason
Use of Graphics to Support Text for Each Topic:Poor: Unclear and Does not Support TextGood: Diagram Matches Text and Aids in Understanding of ConceptExcellent: Diagram Thoroughly Explains Concepts and Could Stand Alone Without Text
Topic Name Description of Graphic Quality
Best Feature(s) of the Site:
How many links were provided for the site/topics?:
Identify specific links that were helpful and/or relevant to the topic(s):
Name of Link Summary of Content Reason it was Helpful
Overall Ratings: On a scale of 1-5 (1 is the lowest and 5 is the best), rate the following:
Visual Appearance of Site ________
Content of Text ________
Use of Graphics ________
Ease of Use ________
Links ________
Helpfulness to your task ________
Overall Rating of Site ________
What is your “bottom line” about this site? (1-2 sentences):
