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Requirement 5

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5. Do the following:

a. Explain the differences between a block diagram and a schematic diagram.


b. Draw a block diagram for a radio station that includes a transceiver, amplifier, microphone, antenna, and feed line.


c. Explain the differences between an open circuit, a closed circuit, and a short circuit.


d. Draw eight schematic symbols. Explain what three of the represented parts do. Find three electrical components to match to three of these symbols.

A block diagram shows the different sections of a transmitter or receiver. 



A more detailed schematic diagram shows all of the individual electrical components used to build the radio.

Click here to see a Transmitter schematic diagram

An open circuit has a break so that electrons cannot flow.  A closed circuit is complete and electrons flow correctly.  A short circuit is where a the electrons take a short cut and don't flow where they should.

Here are some common electronic symbols


Here are some uses of common electronic componets:

Fuse Is a thin wire which breaks  if there is too much current from a short circuit or other problem.
Battery Produces electric energy from chemical energy.
Resistor Slows the flow of electric current
Variable resistor Like a regular resistor, but adjustable. Often used as volume controls.
Earth ground A connection from the  the radio to the earth, usually through a copper pipe driven into the soil.
Chassis ground A connection of the negative side of the electronic circuit to the  frame and case that holds of the equipment.
Capacitor Stores an electric charge. Will let alternating current (AC - like in your house) flow but stops direct current (DC - like from a battery).
Variable capacitor Same as a regular capacitor, but adjustable.  Often used as tuning controls.
NPN transistor Amplifies a current. (NPN is remembered as Not Pointing iN)
PNP transistor Amplifies a current. (PNP is remembered as Pointing iN)
Coil Also called a choke, it works the opposite of a capacitor. It lets DC flow but stops AC.
Tube A vacuum tube made of glass with wire filaments inside. Amplifies a current. It has been replaced by transistors in most home equipment, but is still found in some high power radio transmitters.
Antenna Sends radio frequency signals into the air.
SPST switch Single-pole single-throw switch. Has two positions, on and off. (Most light switches)
DPDT switch Double-pole double-throw switch. A double-throw switch has three positions. It can switch one input to one of two outputs - sort of like the switch you put on your television to switch between watching TV and playing your video game. The double-pole means it can switch a pair of inputs to either of two pairs of outputs.

You have to find three parts if your counselor doesn't have them.  Almost any home has a battery, a lamp, a switch or a fuse.

Requirement 6

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