Radio Shack Return Gps No Recipt

SUBJECT: RADIO AM FM UNIT I

Power Source, transformer, rectifier, filter, regulator

Many circuits needed for operation, a power direct current (DC) , but is usually found power alternating current (AC) .

In order to get current, the AC input must follow a process of conversion as shown in the diagram.

The following chart is the operation of a source, using a block diagram.
also shows the expected waveforms at baseline (AC Input), end (DC output) and between each of them.

- The input signal, which is the primary of transformer , is a sine wave whose amplitude depends on where you live (110/220 Volt AC or other).
- The transformer secondary delivery to your signal with an amplitude less than the input signal and it must have a value that is in keeping with the voltage (voltage) final DC power is desired.

For example if you want a final voltage of 12 volts direct current, the transformer secondary must have an AC voltage of no less than 9 volts, this value being very tight (remember that the secondary peak is : Vp = 1.41 x Vrms = 1.41 x 9 = 12.69 V).



If one takes into account the voltage drops at different stages (blocks) of the power supply may no longer be able to obtain the desired 12 volts.

In this case, choose a transformer with a secondary voltage of 12 volts AC. This AC voltage to obtain a voltage Peak: Vp = 1.41 x 12 = 16.92 volts.


- The rectifier converts the signal prior to a pulsating DC waveform, and in the case of the diagram, using a rectifier 1 / 2 wave (eliminates the negative wave .)


- The filter, consisting of one or more condensers (capacitors) , smooths and flattens the previous wave by eliminating the component of alternating current (AC) gave the rectifier. The capacitors are charged to the maximum value of voltage delivered by the rectifier and slowly discharge when the pulsed signal disappears.


See the diagram above and process of discharging a capacitor
- The controller receives the signal from the filter and delivers a constant voltage regardless of variations in load or supply voltage .


- transformers are used to lower or raise AC voltages.


- Rectifiers are made up of diodes and used the process of transforming an AC signal to DC, allowing the passage or not semicycles AC wave.


- Filters can be of various types and are used to remove unwanted components of CA .- The regulators are a group of elements or an electronic element


Regulator zener diode voltage


Features, design example
The Zener can be used to regulate a voltage source . This semiconductor is manufactured in a wide variety of tensions and powers


These range from less than 2 volts to several hundred volts, and power will be dissipated from 0.25 watts (W) to 50 watts (W) or more.


power dissipated by zener diode is simply multiplies the voltage for which it was manufactured by current flowing through it.


x Vz Pz = Iz


This means that the maximum current that can pass through a zener diode is:


Iz = Pz / Vz.


Where: - Iz = current through the Zener-Pz = power zener diode (manufacturer) - Vz = Zener diode voltage (manufacturer)



Example: The current maximum zener diode 10 Volt and 50 Watts (W) may hold is: Iz = Pz / Vz = 50/10 = 5 amps



Calculation limiting resistor Rs. (See diagram of the regulator with zener diode)

The calculation of the resistance Rs is determined by the load current request (which we to connect to this source.)
This resistance (resistor) can be calculated using the following formula:

Rs = [Venmin - Vz] / 1.1 x ILMAX

where: - Come (min) is the minimum input voltage. (Remember that a voltage is regulated and may vary) - IL (max) is the value of the maximum load current request.

Once earned Rs, we obtain the maximum power zener diode, using the following formula:

PD = [[Venmin - Vz] / Rs - ILmin] x Vz

Example of a Design:

A 15 volt source to feed a load with 9 Volt, which consumes a current that varies between 200 and 350 mA. (Milliamps). Choosing a 9.1-volt zener diode as there is no 9.
- Calculation of Rs: Rs = (15 - 9.1) / (1.1 x 0.35) = 15 ohms (ohms)

- Calculation of power zener diode, PD = [(15 - 9.1) / 15] x 9.1 = 3.58 watts or watts.
Since there is no zener diode of 3.58 Watts, and choose one of 5 watts which is the closest

- Rs Power: An additional calculation is the power of resistance Rs. This is done with the formula: P = I2 x R.

Current data are: I (max) = 350 milliamps = 0.35 amp = Rs 15 ohms (ohms) using the formula, PRS = 0,352 x 15 = 1.84 Watts (Watt) This means that when you buy this resistance (resistor) must be 2 Watts or more

Powerful Workstations 2010

Power Sources Electromagnetic Spectrum Oscillators

SUBJECT: RADIO AM FM UNIT I

SO DOES THE ELECTROMAGNETIC SPECTRUM



RADIATION OF ELECTROMAGNETIC WAVES

oscillation or acceleration of any electrical charge generated a physical phenomenon consisting of electric and magnetic components, spectrum of radiation known as electromagnetic waves.

Fig. 1 full spectrum of radiation of electromagnetic waves.


That spectrum can be ordered from waves that have very low frequencies of a few hertz (Hz) or cycles per second with very long lengths, such as the frequency of the alternating current we use in our houses, until a very high frequency waves, thousands of millions of hertz or cycles per second with extremely short lengths, such as those with cosmic radiation.

The only difference between a wave group and others within the electromagnetic spectrum is the frequency in hertz (Hz), its length in meters (m) and transmit energy level in joules (J).

Main features of electromagnetic waves

The three main characteristics of the waves that constitute the electromagnetic spectrum are:

Frequency (f)

Length (λ)

Amplitude (A)


Frequency

The frequency of a wave corresponds to a physical phenomenon that is repeated cyclically a certain number of times for a second time, as shown in the following illustration:
fig. 2
A. - sine wave cycle or hertz (Hz) per second. B. - Sine wave of 10 cycles or hertz per second

The frequency of these waves of the electromagnetic spectrum are represented by the letter (f) and its unit of measurement is the cycle, or hertz (Hz) second.


wavelength

spectrum electromagnetic waves propagate through space in a similar way as water does when you throw a stone into a pond, that is, generating waves at the point where it falls the stone and extending to the shore.

When we throw a stone into a pond, waves are generated similar to
radiation characteristic of the electromagnetic spectrum.


Both waves are produced by displacement of water as the waves of the electromagnetic spectrum have peaks or ridges and valleys or bellies.

The horizontal distance between two consecutive peaks, two consecutive valleys, or even twice the distance between a node and other electromagnetic wave, measured in multiples or fractions of meters (m), constitutes what is called length wave. "

P. - Peak or crest: the maximum value of positive sign (+), takes the sine wave spectrum. electromagnetic, each half cycle, from the "0". This value increases or decreases as. amplitude "A" of the wave increases or decreases very positively over the value "0."

V. - Valle or womb maximum negative value (-), which takes the sine wave spectrum. electromagnetic, each half cycle, as it descends and crosses the "0". . The value of the valleys. increases or decreases as the amplitude "A" of the wave itself grows or decreases negatively. below the value "0."

T. - Period: time in seconds that elapses between the passage of two peaks or two valleys for the same. point.

N. - Node: Value "0" of the sine wave.

a wave length of the electromagnetic spectrum is represented by the Greek letter lambda. (Λ) and its value can be found using the following mathematical formula:

Where:

λ = wavelength in meters.
c = speed of light in vacuum (300 000 km / sec.)
f = wave frequency in hertz (Hz).

For example, if we want to know what band in meters (SW) transmits a radio station that is captured in the 7.1 MHz frequency on the dial, proceed as follows:



The speed of light (300 000 km / sec) become m / sec, to get the final result in meters. This operation is performed as follows, taking into account that 1 km is equal to 1 000 meters:

300 000 km / sec x 1 000 m = 300 000 000 meters / sec



below the 7.1 megahertz are converted in hertz (Hz), which is the unit of measurement frequency, given that 1 MHz is equal to 106 Hz, or 1 million Hz: 7.1 MHz x

106 = 7.1 x 1 000 000 = 7 100 000 Hz (or 7.1 million cycles per second)



The result of these two conversions substitute their values \u200b\u200bin the above formula and we have: Therefore
, the wavelength of the signal of 7.1 MHz will be 42.2 meters per cycle or hertz frequency. This length corresponds to the range of short wave radio (OC) that respond to the band corresponding range of 41 meters in the face of a receiver.


Wavelength

The amplitude is the maximum value that can reach the crest or peak of a wave. The point of less value received the name of the valley or belly, while the point where the value vanishes in passing, is known as "node" or "zero."

properties of electromagnetic waves

for its propagation of electromagnetic waves do not require a specific material medium, it can travel even outer space.

electromagnetic waves, as mentioned above, are spread by the vacuum at the speed of light (300 000 km / sec approximately), until your energy runs out. As the frequency increases, the wave energy increases.

This type of wave has the same physical properties
wave motion inherent



Research: Mr. Ricardo Arreola Navarro

January 2008 CETIS 58

Subject: Radio AM FM

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