Radio Merit Badge—Part 2 ________________________________________________ ________________________________________________ ________________________________________________ November 19, 2005 ________________________________________________ Presented by John Chamberlain AC5CV ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ 12-13 A Radio StationStation ________________________________________________ Transmitter ________________________________________________ Creates radio waves at a desired frequency (tuning). Adds information to those waves. ________________________________________________ For example, takes information (a microphone) from a voice and adds that to the radio waves (“modulation”). ________________________________________________ Receiver Receives radio signals of all frequencies. ________________________________________________ Amplifies the radio waves of a desired frequency (tuning). ________________________________________________ Converts the information in the waves to audio frequencies: output through a speaker. Transceiver: Transmitter and Receiver in one unit. ________________________________________________ ________________________________________________ 12-13 A Radio StationStation ________________________________________________ Amplifier ________________________________________________ Greatly increases the voltage (the strength) of the electric waves coming out of the transmitter. ________________________________________________ This generally helps your signal reach farther (up to a point). ________________________________________________ Antenna When transmitting: acts like a megaphone, lets the electric ________________________________________________ waves spread out in the desired direction. When receiving: acts like a “big ear” that collects the electric ________________________________________________ wave energy. To be most efficient, antennas must be “tuned” to the radio ________________________________________________ frequency, just like the the transmitter and receiver are tuned. ________________________________________________ Radio Merit Badge, Part 2 12-13 Antennas: The Dipole ________________________________________________ Size of the antenna is based on ________________________________________________ the frequency, or the wavelength. λ ________________________________________________ ________________________________________________ Total dipole length equals half the “wavelength” ________________________________________________ Length (in ft) = 468/f where f=freq in MHz 38.5 in. ________________________________________________ Example: for f = 146 MHz ________________________________________________ Length = 468/146 = 3.2 ft, Transceiver 146 MHz or 38.5 inches ________________________________________________ 12-13 Antennas: “Whips” ________________________________________________ Vertical whips are often attached to a ________________________________________________ magnet. ________________________________________________ Often called “a “mag-mount.” ________________________________________________ Typically, they are ¼ wavelength, but 5 can also be ⁄8 wavelength. ________________________________________________ Magmounts require a metal surface— ________________________________________________ both physically, and electrically. ________________________________________________ ________________________________________________ 12-13 Antennas:Antennas: “Beams” ________________________________________________ Parallel “dipoles” ________________________________________________ strengthen the signal in ________________________________________________ one direction. They “beam” the radio ________________________________________________ signal in one main ________________________________________________ direction. Also receive the signals from that same ________________________________________________ direction. ________________________________________________ ________________________________________________ John Chamberlain, AC5CV Page 2 Radio Merit Badge, Part 2 12-13 Antennas of all shapes! ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ SafSafetyety FirFirstst!! ________________________________________________ Working on radios can be dangerous! ________________________________________________ They use electricity: often very high voltages! ________________________________________________ Radio waves themselves can cause burns! So, don’t touch an antenna when someone is ________________________________________________ transmitting! PLEASE: DON’T DO ANY WORK ON ________________________________________________ ELECTRONIC EQUIPMENT YOURSELF until you have learned from an experienced worker. ________________________________________________ And, did you know? It is illegal to work on radio ________________________________________________ transmitters without a license! ________________________________________________ SafSafetyety FirFirstst!! ________________________________________________ Electrical shock can hurt or kill you! ________________________________________________ Make sure the power is disconnected ________________________________________________ before working. Even with the power off, some parts ________________________________________________ inside the radio can hold a dangerous ________________________________________________ electrical charge. If you aren’t sure what you are doing: ________________________________________________ GET HELP! ________________________________________________ ________________________________________________ John Chamberlain, AC5CV Page 3 Radio Merit Badge, Part 2 SafSafetyety FirFirstst!! ________________________________________________ Radio Frequency (RF) energy can ________________________________________________ burn you badly. Keep antennas out of ________________________________________________ reach of people and animals. RF radiation can be unhealthy. Don’t ________________________________________________ use a radio when it is not completely assembled. The case keeps the RF ________________________________________________ radiation contained. ________________________________________________ Make sure the antennas can’t touch any power lines, or you could be ________________________________________________ electrocuted when using the radio. ________________________________________________ SafSafetyety FirFirstst!! ________________________________________________ Lightning can hit your antenna and ________________________________________________ travel down your lines to the radio. Make sure your antenna and radio are ________________________________________________ grounded to a good “earth ground.” ________________________________________________ Be very careful working on towers and roofs. ________________________________________________ A fall will surely hurt you, and might even KILL you! ________________________________________________ Falling tools or other objects can hurt people below. ________________________________________________ ________________________________________________ Block DiagramDiagram vs. Schematic Diagram ________________________________________________ Block diagram ________________________________________________ Shows parts of radio station. ________________________________________________ Schematic diagram ________________________________________________ Shows how the electrical circuit works. It uses schematic symbols to show the path of a ________________________________________________ circuit—similar to the way a map uses “map symbols” to show the path of travel on a hiking ________________________________________________ trail. ________________________________________________ ________________________________________________ John Chamberlain, AC5CV Page 4 Radio Merit Badge, Part 2 Block DiagramDiagram of Radio ________________________________________________ ________________________________________________ Ant ________________________________________________ Ant Mic Transceiver Amp Tuner Feedline ________________________________________________ Power ________________________________________________ Supply ________________________________________________ ________________________________________________ ________________________________________________ Circuits ________________________________________________ An electrical circuit is made up of wires and ________________________________________________ various electrical components ________________________________________________ Together they make up the electronic part of your electrical appliance, in this case: a ________________________________________________ radio. ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ Kinds of Circuits ________________________________________________ Open circuit: No current. No electrical contact. ________________________________________________ For example, when a light switch is