from Educators' eZine
As a science educator, I strive to show students how the topics they are studying link to the “real” world. The need for putting curricula in context was brought home to me some thirty years ago, when one of my students asked me, then a beginning teacher, “Why do we have to study this?”
I had no good answer at the time, but gradually the question completely reshaped what I teach and how I teach it. The purpose of this article is to describe one of the exciting “windows on the world” that can be opened up in your classroom using an interesting scientific instrument accessible on the Internet. The technology of remote Web-controlled radio receivers described in this article can be applied to language arts and social studies curricula as well as to science.
What is a Web-controlled receiver?
A Web-controlled receiver is typically a high quality general coverage radio receiver with an appropriate outdoor antenna, a so called “long wire.” The frequency range of the receiver is typically 0-30 MHz or more, covering the long-, medium- (AM broadcast) and shortwave bands. The receiver is located at a remote site and can be tuned and adjusted via a Website. Thus, students can operate the receiver from an Internet linked computer in the classroom.
Using Web-controlled receivers in science curricula
One topic typically covered in middle school science curricula is electromagnetism. Beyond building an electromagnet with wire, a nail, and a battery to demonstrate how a switch or relay works, how can students study this phenomenon in a way connected to the real world? My suggestion is to have them observe electromagnetic radiation first hand by collecting data on the characteristics of real radio waves broadcast in the shortwave bands.
While most students are familiar with the AM or FM radio stations they might listen to daily, I’ve found very few who know about shortwave broadcasting stations. These high power stations beam signals around the world in portions of the electromagnetic spectrum known as the shortwave bands. The broadcasts contain a wide variety of news, music, cultural and other programming from host nations. As physicists know, the radio waves transmitted by shortwave stations are “shorter” than those of the AM band (those are hundreds of meters long) but actually longer than those transmitted by stations on the FM band (a few meters long).
Radios waves broadcast by shortwave stations are mostly in the range of sixty to fifteen meters long. These waves have the interesting characteristic of being variously reflected by the charged particles in layers of the ionosphere and returning to the Earth at great distances from the transmitting stations and thus are instructive to observe.
To observe radio waves broadcast by shortwave stations, show your students how to find a schedule of broadcasts. This can be done by going to one of any number Websites with this information. One example is “Prime Time Shortwave.” Here you can find the time, country, station call letters, and frequencies of broadcasts. Note that the times of broadcasts are in UTC and the Website has a time converter to show your equivalent local time.
Next show your students how to access and use a remote Web-controlled shortwave receiver. There are a number of sites on the Internet that offer these receivers. Some are free while others require a small subscription fee. All of the Web-controlled receivers I have used are offered on a shared basis. Make sure to check out any receiver site before you use it in class, or send your students to use it, so that everybody is familiar with the user requirements and rules. The little effort you take to find and learn how to use Web- controlled receivers sites will be rewarded with access to professional quality receiver installations around the world. Examples of Web-controlled receivers can be found at “The Original Web-Controlled Shortwave Radio” and DX TUNERS.
Plan a classroom investigation
Plan for your students to do an investigation of radio waves in over a period of several weeks. Have the students work in groups to use the remote web-controlled receivers to listen for and record data on shortwave broadcasts in several bands, I suggest they start by trying to hear stations in the 49 and 25-meter bands. See “Shortwave Bands” for the frequencies and characteristics of these bands.
Have each group maintain a journal of what they are able to observe using the Web-controlled receivers. They should make their observations at various times, both during daylight hours and after sunset. The journal entries should include the following data: date, time, frequency, band and call sign or name of particular stations heard. Students should also estimate and document the strength of the signal of each station heard. Have them use a signal strength estimation scale ranging from 1, for a weak signal, to 5, for a strong signal, with 3 being a medium strength signal.
An example of a journal entry would be as follows:
Time: 7:56pm (or “1956” if using 24-hour clock)
Frequency: 5960 kHz
Call Sign / Name: Radio Thailand
Signal Strength: 5
Aim to have each group document data on 20 or more different stations, ten in the 49-meter band and ten in the 25-meter band.
After several weeks of shortwave listening using the web-controlled receivers, have each group create a table or chart of their journal data. Post the charts all together in the classroom and ask the students what conclusions they can draw from the data. Ask them to make inferences about the data on the charts.
Students should be able to conclude from their data that stronger signals are heard in the 25-meter band during the day than after sunset when almost no stations are heard. After sunset stronger signals and more stations are heard in the 49-meter band. They may infer that signals of different frequencies travel differently depending on time of day.
During this discussion relate their findings to the idea of radio waves being a form of electromagnetic radiation that, like light, can be reflected. Bounce a foam ball off the ceiling to show how radios waves bounce off the ionosphere. As the students have discovered, shortwave stations broadcasting in the 25-meter band have strong daytime signals because they bounce off the charged particles in the ionosphere. After the Sun sets the 25-meter signals disperse into space but the signals of 49 meter broadcast stations are reflected back to Earth with strong signals.
Electromagnetism is a force of nature that people use everyday around the world, not simply a topic in a science book! In fact, millions of people listen to shortwave broadcasts daily.
Web-controlled receivers across the curriculum
The Web-controlled receivers can be used in other content areas too. Shortwave broadcast are rich in cultural perspective and content, making them ideal for social studies projects. Language arts classes can be enhanced too by giving students access to authentic language and stories from around the globe. However you choose to use Web-controlled receivers they are a relatively new technological application that allows you as a teacher to connect curricula with the “real” world.
Email:Kevin C. Wise