* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Electricity, Electronics and Ham Radio
Telecommunications engineering wikipedia , lookup
Power electronics wikipedia , lookup
Yagi–Uda antenna wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Wave interference wikipedia , lookup
Surge protector wikipedia , lookup
Telecommunication wikipedia , lookup
Radio receiver wikipedia , lookup
Spark-gap transmitter wikipedia , lookup
Current mirror wikipedia , lookup
Opto-isolator wikipedia , lookup
Regenerative circuit wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
RLC circuit wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Rectiverter wikipedia , lookup
Crystal radio wikipedia , lookup
Direction finding wikipedia , lookup
Radio transmitter design wikipedia , lookup
Electricity, Electronics And Ham Radio “Kopertroniks” By Nick Guydosh 4/12/07 Electricity Basics • Electricity: a stream of electrons flowing through a wire • Similar to water flowing through a hose – Water current – Pressure (pump) voltage (battery) – The hose wire • Circuit: electricity flowing in a loop – Similar to the cooling system in a car – The resistance of a device (radiator) to the water is like a resistor in an electrical circuit – The pump is like the battery Electricity Basics • Two kinds of electricity: – Alternating current (AC): electrons vibrate back and forth • Example: generator or car alternator • Frequency: number of vibrations (cycles)/sec – Direct Current (DC): Electrons flow in one direction • Example: battery • How do we measure electricity? – Voltage: “volts” – Current: “amperes” or amps or A Electrical Components • Components (symbols given): – Voltage source – drives the electricity in circuit example: a battery or generator. measured on volts DC AC – Resistor: Resists the flow of current measured in “Ohms” or Ω – Capacitor: stores electrical energy (electrons} measured in “farads” two plates – Inductor: stores magnetic energy from the current. Measured in “henrys” a coil of wire • Electrical quantities use numerical prefixes: – Ex: 2000 ohms = 2K Ω or 2K, 1/1000 amp =1 milliamp or ma Circuits • A circuit is a network of “components” through which electricity may flow. – For all practical purposes – all closed loops • Example: Resistive Circuits • Basic Law of electricity – “Ohms Law” – Tells us how much current will flow in a resistor for some given amount of voltage across it. = IxR – I = V/R Three versions: V=IxR I=V/R R=V/I Example: 2 D cell (V = 3 volts) R = 560 ohms I = V/R =3/560 = 0.0054A = 5.4ma Series/Parallel Circuits • Lets look ar how we can hook up two resistors in a circuit: Questions: How would the voltage and current split up if R1 = R2? Voltage division: Current division: If you are measuring Voltage, how would you hook the meter probes? Same question for Current. A question • Is it possible for a current to flow if the circuit is not physically connected in a loop? – For example a capacitor is just two plates separated by space of an insulator: – Example 1: What happens when the switch is closed: Current flows for a short time As the capacitor charges up To full voltage V A question • What happens if we replace the DC voltage supply in the previous example with an AC source? I AC current flows will flow continuously as the capacitor continuously charges and discharges; Current though capacitor vs time Basics of Radio • Lets switch gears to AC electricity – Electrons are vibrating back & forth – as in the previous example. – Their speed is constantly changing as it continually reverses direction. – In other words, the electrons are accelerating and decelerating constantly. • Fundamental principle: Whenever an electron (or charge) is accelerated it will radiate radio waves! … principle of “electromagnetic radiation” could be microwaves or light waves if vibrations are fast enough – high frequencies. Electromagnetic Propagation • Radio waves or any light waves, for that matter, are made up of: Electric field (red) – as from a charged up comb Magnetic field (blue) – as from a magnet (or electromagnet) They are perpendicular to each other And vibrate & fly though empty space at 186,000 mi/sec http://micro.magnet.fsu.edu/primer/java/polarizedlight/emwave/index.html Radio Transmission • Just as AC current could “flow” though a capacitor (charging & discharging): – High frequency currents could also flow into an antenna. – They produce radio waves (our basic principle) Vibrating current Outgoing Radio waves dipole antenna Vibrating current Transmitter Cable to antenna Radio Receiving • The process can be reversed! • Radio waves hitting an antenna will induce high frequency currents in the antenna – they could be detected by a radio receiver. incoming Radio waves dipole antenna Vibrating current Receiver Cable from antenna Combine the two Together & we have A Transceiver! Sending Information On Radio Waves • OK – so we now could send and receive radio signals – how do we get our voice on the air? • If we convert voice waves (audio) to electrical waves, the frequencies would be less that 20,000 cycles per second (20 KHz). – This is much too low for creating efficient radio waves. – We need frequencies of many millions of cycles per second or higher – MHz to GHz. – So what do we do now? • The answer is to “modulate” a high frequency “carrier” with our audio frequency (voice) signal Modulation • It is not efficient to walk from NY to CA so we us a carrier – an aircraft vs • In radio we use a carrier signal is some high frequency, say 1290 Khz or 1,29 Mhz ( a local radio station) Note: • The audio signal causes the amplitude of the carrier to vary as the value of the signal varies. Note: frequency = speed of light / wavelength Amplitude Modulation (AM) How its done: Frequency Modulation (FM) Less sensitive to noise Typically used higher carrier frequencies A Simulation of Modulation Putting it together Receive antenna Transmit antenna Modulate Radio waves Audio De-Modulate Carrier RF amplifier Audio amp audio Lab Exercise #1 – series Circuit Lab Exercise #1 – series Circuit - probe Lab Exercise #2 – parallel Circuit Lab Exercise #2 – parallel Circuit – probe total current Lab Exercise #2 – parallel Circuit – probe current in one parallel resistor