FUNCTION GENERATOR

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Notes:

This function generator, based on an LT016 high-speed comparator, will generate from a single +5-V supply. The slow rate of the op amps used determines the maximum useable frequency of this circuit.
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Amazing...Formulas

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Soldering Instructions

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SINE-WAVE SHAPER

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Unlike most sine-wave shapers, this circuit is temperature stable. It varies the gain of a transconductance amplifier to transform an input triangle wave into a good sine-wave approximation.


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SIMPLE STAIRCASE GENERATOR

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U2 is a decade counter/divider. U1 is used as a switch debouncer. For a self-generating system, connect a resistor between pins 2 and 3 of a U1 value that should be between 10 k ohm and several M ohm, depending on desired frequency. C1 can also be varied to change frequency. Also, S1 can be omitted in the self-generating version.
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Fridge door Alarm

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Beeps if you leave open the door over 20 seconds 3V battery operation, simple circuitry

 

 

R1____________10K   1/4W Resistor
R2___________Photo resistor (any type)
R3,R4________100K   1/4W Resistors

C1____________10nF  63V Polyester Capacitor
C2___________100µF  25V Electrolytic Capacitor

D1,D2_______1N4148  75V 150mA Diodes

IC1___________4060  14 stage ripple counter and oscillator IC

Q1___________BC337  45V 800mA NPN Transistor

BZ1__________Piezo sounder (incorporating 3KHz oscillator)

SW1__________Miniature SPST slide Switch

B1___________3V Battery (2 AA 1.5V Cells in series)
 
This circuit, enclosed into a small box, is placed in the fridge near 
the lamp (if any) or the opening. With the door closed the interior of 
the fridge is in the dark, the photo resistor R2 presents a high 
resistance (>200K) thus clamping IC1 by holding pin 12 high. When a 
beam of light enters from the opening, or the fridge lamp illuminates, 
the photo resistor lowers its resistance (<2K), pin 12 goes low, IC1 
starts counting and, after a preset delay (20 seconds in this case) the 
piezo sounder beeps for 20 sec. then stops for the same lapse of time 
and the cycle repeats until the fridge door closes. D2 connected to pin 6
 of IC1 allows the piezo sounder beeping 3 times per second.
 
 
  • Connecting D1 to pin 2 of IC1 will halve the delay time.
  • Delay time can be varied changing C1 and/or R3 values.
  • Any photo resistor type should work.
  • Quiescent current drawing is negligible, so SW1 can be omitted.
  • Place the circuit near the lamp and take it away when defrosting, to avoid circuit damage due to excessive moisture.
  • Do not put this device in the freezer.
 

 

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Speech Amplifier

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Parts:

P1______________22K  Log. Potentiometer

R1_______________1M  1/4W Resistor
R2______________15K  1/4W Resistor
R3_____________470R  1/4W Resistor
R4______________47K  1/4W Resistor
R5,R6____________4K7 1/4W Resistors (Optional, see Notes)

C1,C2,C4_______100nF  63V Polyester or Ceramic Capacitors
C3______________10nF  63V Polyester or Ceramic Capacitor (See text)
C5_____________220µF  25V Electrolytic Capacitor
C6______________10µF  25V Electrolytic Capacitor (Optional, see Notes)

Q1____________BC547   45V 100mA General purpose NPN Transistor

IC1_________TDA7052  Audio power amplifier IC

J1______________3mm or 6mm Mono Jack socket

SW1____________SPST  Slider Switch fitted in the microphone (Optional, see text)
SW2____________SPST  Toggle or Slider Switch

SPKR______________4-8 Ohm Loudspeaker (See Notes)

B1_______________6V  Battery (4 x AA or AAA 1.5V Cells in series
                              or any 6V rechargeable battery pack etc.)
 
 
This circuit is intended to be placed in the same box containing the loudspeaker, forming a compact microphone amplifier primarily intended for speech reinforcement. A device of this kind is particularly suited to teachers, lecturers, tourists' guides, hostesses and anyone speaking in crowded, noisy environment.
The circuit's heart is formed by the TDA7052 Audio power amplifier IC, delivering a maximum output of 1.2W @ 6V supply. An external microphone must be plugged into J1, its signal being amplified by Q1 and fed to IC1. R1 acts as a volume control and C3 tailors the upper audio frequency band, mainly to reduce the microphone possibility of picking-up the loudspeaker output, causing a very undesirable and loud "howl", i.e. the well known Larsen effect.
Therefore, C3 value can be varied in the 4n7 - 22nF range to ensure the best compromise from speech tone quality and minimum Larsen effect occurrence. For the same reason, the use of an uni-directional (cardioid) dynamic or electret microphone is warmly recommended.
Most of these microphone types are usually fitted out with a slider switch: this is an useful feature that can be used to momentarily mute the microphone. Some microphone types use a separate jack for connection to the muting circuit, some others use a stereo jack or different plug types. In any case, the connection of this switch to the circuit is shown as SW1 in the diagram.

Notes:

  • Please note that hands-free, uni-directional headset or earclip microphone types are very well suited for this device, as also are Clip-on Lavalier or Lapel microphones.
  • If a small electret capsule is used for the microphone, R5, R6 and C6 must be added to the circuit to provide power supply.
  • Choose a loudspeaker as large as possible, in order to increase circuit performance.
  • You can use also two 4 Ohm loudspeakers wired in series or two 8 Ohm types wired in parallel in order to obtain better results.
  • The box containing the amplifier and loudspeaker(s) can be fitted out with a belt and carried like a shoulder-bag or, if you build a smaller unit, it can be used as a Pick & Go Belt Clip Speaker.
 
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SINGLE SUPPLY FUNCTION GENERATOR

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The circuit has both square-wave and triangle-wave output. The left section is similar in function to a comparator circuit that uses positive feedback for hysteresis. The inverting input is biased at one-half the Vcc voltage by resistor R4 and R5. The output is fed back to the non-inverting input of the first stage to control the frequency. The amplitude of the square wave is the output swing of the first stage, which is 8V peak-to-peak. The second stage is basically an op amp integrator. The resistor R3 is the input element and capacitor C1 is the feedback element. The ratio R1/R2 sets the amplitude of the triangle wave, as referenced to the square-wave output. For both waveforms, the frequency of oscillation can be determined by the equation:

fo= 1/4R3C1 * R2/R1

The output frequency is approximately 50 Hz with the given components.
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HIGH FREQUENCY SIGNAL GENERATOR

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A tapped-coil Colpitts oscillator is used at Q1 to provide four tuning ranges from 1.7 to 3.1 MHz, 3.0 to 5.6 MHz, 5.0 to 12 MHz and 11.5 to 31 MHz. A Zener diode (D2) is used at Q1 to lower the operating voltage of the oscillator. A small value capacitor is used at C5 to ensure light coupling to the tuned circuit. Q2 is a source-follower buffer stage. It helps to isolate the oscillator from the generator-output load. The source of Q2 is broadly tuned by means of RFC1. Energy from Q2 is routed to a fed-back, broadband class-A amplifier. A 2 dB attenuator is used at the output of T1 to provide a 50 ohm termination for Q3 and to set the generator-output impedance at 50 ohms. C16, C17 and RFC2 form a brute-force RF decoupling network to keep the generator energy from radiating outside the box on the 12 V supply.         

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555 timer with LED

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BUTLER APERIODIC OSCILLATOR

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Notes:

This circuit works well in the range of 50 kHz to 500 kHz. Slight component modifications are needed for higher frequency operation. For operation over 3000 kHz, select a transistor that provides moderate gain (in the 60 to 150 range) at the frequency of operation and a gain-bandwidth product of at least 100 MHz.
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1-TO 4-MHZ CMOS OSCILLATOR

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Notes:

1. 1 M ohm < R1 < 5 M ohm. 
2.  Select R2 and C2 to prevent spurious frequency. 
3.  ICs are 74C04 pr equivalent.
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10-TO 80-MHZ OSCILLATOR

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Notes:

1.  Y1 is "AT" cut, fundamental, or overtone crystal. 
2.  Tune L1 and C2 to operating frequency.
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CMOS CRYSTAL OSCILLATOR

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Notes:

This circuit has a frequency range of 0.5 Mhz to 2.0 Mhz. Frequency can be adjusted to a precise value with trimmer capacitor C2. The second NOR gate serves as an output buffer. 
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Ramp Generator

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The 566 can be wired as a positive or negative ramp generator. In the positive ramp generator, the external transistor driven by the Pin 3 output rapidly discharges Cl at the end of the charging period so that charging can resume instantaneously. The pnp transistor of the negative ramp generator likewise rapidly charges the timing capacitor Cl at the end of the discharge period. Because the circuits are reset so quickly, the temperature stability of the ramp generator is excellent. The period

T  is  1/2 fo

where f, is the 566 free-running frequency in normal operation. Therefore,

                                                T  =   1    =   Rt C1 Vcc
                                                         2fo      5(Vcc - Vc)

where Vc is the bias voltage at Pin 5 and Rt is the total resistance between Pin 6 and Vcc. Note that a short pulse is available at Pin 3. (Placing collector resistance in series with the external transistor collector will lengthen the pulse.)
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CRYSTAL TESTER

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Notes:

Q1 acts as a Colpitts crystal oscillator, and if the crystal under test is operational, the RF signal is rectified by D1 and D2, turning on Q2 and lighting indicator LED2. LED1 is a power indicator
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FM Bug Detector

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This circuit can be used to "sweep" an area or room and will indicate if a surveillance device is operative. The problem in making a suitable detector is to get its sensitivity just right; too much and it will respond to radio broadcasts, too little sensitivity and nothing will be heard.


This project has few components, can be made on veroboard and powered from a 9 volt battery for portability. 



 Circuit operation is simple. The inductor is a moulded RF coil, value of 0.389uH and is available from Maplin Electronics, order code UF68Y. (See my links page for component suppliers.) The coil has a very high Q factor of about 170 and is untuned or broadband. With a test oscillator this circuit responded to frequencies from 70 MHz to 150 MHz, most of the FM bugs are designed to work in the commercial receiver range of 87 - 108 MHz. The RF signal picked up the coil, and incidentally this unit will respond to AM or FM modulation or just a plain carrier wave, is rectified by the OA91 diode. This small DC voltage is enough to upset the bias of the FET, and give an indication on the meter. The FET may by MPF102 or 2N3819, the meter shown in the picture is again from Maplin Electronics, order code LB80B and has a 250 uA full scale deflection. Meters with an FSD of 50 or 100 uA may be used for higher sensitivity.


In use the preset is adjusted for a zero reading on the meter. The detector is then carried around a room, a small battery transmitter will deflect the meter from a few feet away.
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WAP to find the cube of the number in the range 0h to fh

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org 0h
mov r0,#20H
mov a,@r0                 ;num in 20h is loaded into acc and b reg
mov 0f0h,a
mul ab                         ;find the square of the no.
mov 0f0h,@r0
mul ab                       ;multiply square of the no. by the no.to get the cube.
mov 030h,a                   ;lower order product in 30h
mov 031h,0f0h               ;higher order product in 31h
here: sjmp here
end
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Basic PICAXE parameters

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Here are some of the most useful parameters of the PICAXE:
• The PICAXE requires 5 volts DC, regulated.

• The inputs and outputs of the PICAXE are compatible
with 5-volt logic chips. You can attach them directly.
• Each PICAXE pin can sink or source up to 20mA. The
whole chip can deliver up to 90mA. This means that
you can run LEDs directly from the pins, or a piezo
noisemaker (which draws very little current), or a
transistor.
• You can use a chip such as the ULN2001A Darlington
array (mentioned in the previous experiment) to amplify
the output from the PICAXE and drive something
such as a relay or a motor.
• The chip executes each line of your program in about
0.1 milliseconds.
• The 08M chip has enough flash memory for about 80
lines of program code. Other PICAXE chips have more
memory.
• The PICAXE provides 14 variables named b0 through
b13. The “b” stands for “byte,” as each variable occupies
a single byte. Each can hold a value ranging from 0
through 255.
• No negative or fractional values are allowed in
variables.
• You also have 7 double-byte variables, named w0
through w6. The “w” stands for “word.” Each can hold a
value ranging from 0 through 65535.
• The “b” variables share the same memory space as the
“w” variables. Thus:
• b0 and b1 use the same bytes as w0.
• b2 and b3 use the same bytes as w1.
• b3 and b4 use the same bytes as w2.
• b5 and b6 use the same bytes as w3.
• b7 and b8 use the same bytes as w4.
• b9 and b10 use the same bytes as w5.
• b11 and b12 use the same bytes as w6.
• b13 and b14 use the same bytes as w7.
Therefore, if you use w0 as a variable, do not use b0 or
b1. If you use b6 as a variable, do not use w3, and so on.
• Variable values are stored in RAM, and disappear when
the power is switched off.
• The program is stored in nonvolatile memory, and
remains intact when the power is off.
• The manufacturer’s specification claims that the
nonvolatile memory is rewritable up to about 100,000
times.
• If you want to attach a switch or pushbutton to a pin
and use it as an input, you should add a 10K pull-down
resistor between the pin and the negative side of the
power supply to hold the pin in a low state when the
switch is open. Figure 5-143 shows how pull-down
resistors should be used in conjunction with a SPST
switch or a pushbutton.
• On the 08M chip, if you apply a varying resistance
between Logic Pins 1, 2, or 4, and the negative side of
the power supply, the chip can measure it and “decide”
what to do. This is the “Analog-Digital Conversion”
feature—which leads to our next experiment.
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WAP to convert BCD to ASCII

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org 0h
start: mov r0,#20h       ;r0 pointing to src location,loaded with a BCD no.
mov a,@r0                ;no. moved to accumulator and added 30h to get equivalent
                                  ;ASCII
add a,#30h
mov 40h,a                  ;result stored at 40h
sjmp start
end
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WAP to convert given hex no. to equivalent decimal no.

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org 0h
start:
mov dptr,#5fffh
movx a,@dptr
mov 0f0h,#064h                ;Load B reg with 100d or 64h
div ab                              ;Hundreds
inc dptr
movx @dptr,a            ;store in external ram
mov a,0f0h                 ;remainder from b reg to acc
mov 0f0h,#0ah          ; Load B reg with 10d or 0ah
div ab;
inc dptr;
movx @dptr,a            ;store tens in external ram
inc dptr
mov a,0f0h
movx @dptr,a               ;store units in ext ram
here: sjmp here
end
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WAP to move a block of data within the internal RAM

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Org 0h
start1: mov r0,#40h    ;r0 pointed to internal RAM 40h
mov r1,#30h             ;r1 pointing to internal RAM 030h
mov r2,#5                   ;r2 loaded with no. of elements in the array
Start:
mov a,@r0                ;data transfer
mov @r1,a
inc r0
inc r1
djnz r2,start                   ;decrement r2,if not equal to 0,continue with data
                                       ;transfer process.
Sjmp Start1
end
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Byte and word data transfer in different addressing modes

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DATA SEGMENT
DATA1 DB 23H
DATA2 DW 1234H
DATA3 DB 0H DATA4
DW 0H
DATA5 DW 2345H,6789H
DATA ENDS
CODE SEGMENT
ASSUME CS:CODE,DS:DATA
START: MOV AX,DATA   ;Initialize DS to point to start of the memory
MOV DS,AX                  ;set aside for storing of data
MOV AL,25X             ;copy 25H into 8 bit AL register
MOV AX,2345H          ;copy 2345H into 16 bit AX register
MOV BX,AX           ;copy the content of AX into BX register(16 bit)
MOV CL,AL              ;copy the content of AL into CL register
MOV AL,DATA1        ;copies the byte contents of data segment
                                   ;location DATA1 into 8 bit AL
MOV AX,DATA2       ;copies the word contents of data segment memory
                                  ;location DATA2 into 16 bit AX
MOV DATA3,AL          ;copies the AL content into the byte contents of data
                                   ;segment memory location DATA3
MOV DATA4,AX      ;copies the AX content into the word contents of
                                ;data segment memory location DATA4
MOV BX,OFFSET DATA5       ;The 16 bit offset address of DS memeory location
                                           ; DATA5 is copied into BX
MOV AX,[BX]         ; copies the word content of data segment
                                 ;memory location addressed by BX into
                               ;AX(register indirect addressing)
MOV DI,02H                ;address element
MOV AX,[BX+DI}        ; copies the word content of data segment
                               ;memory location addressed by BX+DI into
                                 ;AX(base plus indirect addressing)
MOV AX,[BX+0002H]  ; copies the word content of data segment
                                     ;memory location addressed by BX+0002H into
                                        ;(16 bit)
MOV AL,[DI+2]                                ;register relative addressing
MOV AX,[BX+DI+0002H]                ;copies the word content of data segmen
                                                          ;memory location addressed by BX+DI+0002H
                                                         ;into AX(16 bit)
MOV AH,4CH                 ; Exit to DOS with function call 4CH INT
21H
CODE ENDS                     ; Assembler stop reading
END START
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ASSEMBLING AND EXECUTING THE PROGRAM

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Writing an ALP
Assembly level programs generally abbreviated as ALP are written in text editor EDIT.
Type EDIT in front of the command prompt to open an untitled text file.
EDIT<file name>
After typing the program save the file with appropriate file name with an extension .ASM
Ex: Add.ASM
Assembling an ALP
To assemble an ALP we needed executable file calledMASM.EXE. Only if this file is in
current working directory we can assemble the program. The command is
MASM<filename.ASM>
If the program is free from all syntactical errors, this command will give the OBJECT file. In
case of errors it list out the number of errors, warnings and kind of error.
Note: No object file is created until all errors are rectified.
Linking
After successful assembling of the program we have to link it to get Executable file.
The command is
LINK <File name.OBJ>
This command results in <Filename.exe> which can be executed in front of the command
prompt.
Executing the Program
Open the program in debugger by the command (note only exe files can be open)by the
command.
CV <Filename.exe>
This will open the program in debugger screen where in you can view the assemble code
with the CS and IP values at the left most side and the machine code. Register content
, memory content also is viewed using VIEW option of the debugger.
Execute option in the menu in the menu can be used to execute the program either in
single steps (F8) or burst execution (F5).
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HAPPY BIRTHDAY TO SIR MAX PLANCK

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Max Karl Ernst Ludwig Planck, (April 23, 1858 – October 4, 1947) was a German theoretical physicist who originated quantum theory, which won him the Nobel Prize in Physics in 1918.

Planck made many contributions to theoretical physics, but his fame rests primarily on his role as originator of the quantum theory. This theory revolutionized human understanding of atomic and subatomic processes, just as Albert Einstein’s theory of relativity revolutionized the understanding of space and time. Together they constitute the fundamental theories of 20th-century physics. Both have led humanity to revise some of its most cherished philosophical beliefs,[citation needed] and have brought about industrial and military applications that affect many aspects of modern life.
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Propagation modes in radio communication

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Propagation Modes::
· Ground-wave propagation
o Follows contour of the earth
o Can Propagate considerable distances
o Ground Wave = Direct Wave + Reflected Wave + Surface Wave
o At MF and in the lower HF bands, aerials tend to be close to the ground (in terms of
wavelength). Hence the direct wave and reflected wave tend to cancel each other
out (there is a 180 degree phase shift on reflection). This means that only the
surface wave remains.
o A surface wave travels along the surface of the earth by virtue of inducing currents in
the earth. The imperfectly conducting earth leads to some of its characteristics. Its
range depends upon: Frequency, Polarization, Location and Ground Conductivity.
o The surface waves dies more quickly as the frequency increases:

· Sky-wave propagation
o Signal reflected from ionized layer of atmosphere back down to earth
o Signal can travel a number of hops, back and forth between ionosphere and
earth’s surface
o Reflection effect caused by refraction
· Line-of-Sight propagation (LOS)
· Non-LOS propagation
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Some important parameters in radio communication

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Ducting::
· A duct is something that will confine whatever is traveling along it into a narrow
‘pipe’.
· The atmosphere can assume a structure that will produce a similar effect on radio
waves. When a radio wave enters a duct it can travel with low loss over great
distances. The atmosphere will then act in the manner of a giant optical fiber,
trapping the radio wave within the layer of high refractive index.
· A wave trapped in a duct can travel beyond the radio horizon with very little loss,
producing signal levels within a few dB of the free-space level.
Scattering::
· When an electromagnetic wave is incident on a rough surface, the wave is not so
much reflected as “scattered”.
· Scattering is the process by which small particles suspended in a medium of a
different index of refraction diffuse a portion of the incident radiation in all directions.
· Scattering occurs when incoming signal hits an object whose size in the order of the
wavelength of the signal or less.
Reflection::
· Reflection occurs when signal encounters a surface that is large relative to the
wavelength of the signal
· Radio waves may be reflected from various substances or objects they meet during
travel between the transmitting and receiving sites.
· The amount of reflection depends on the reflecting material.
o Smooth metal surfaces of good electrical conductivity are efficient reflectors of
radio waves.
o The surface of the Earth itself is a fairly good reflector.
· The radio wave is not reflected from a single point on the reflector but rather from an
area on its surface. The size of the area required for reflection to take place depends
on the wavelength of the radio wave and the angle at which the wave strikes the
reflecting substance.
· When radio waves are reflected from flat surfaces, a phase shift in the alternations of
the wave occurs
· The shifting in the phase relationships of reflected radio waves is one of the major
reasons for fading.
Refraction
· Refraction it is the bending of the waves as they move from one medium into
another in which the velocity of propagation is different.
· This bending, or change of direction, is always toward the medium that has the lower
velocity of propagation.
Difraction::
· Diffraction is the name given to the mechanism by which waves enter into the
shadow of an obstacle.
· Diffraction occurs at the edge of an impenetrable body that is large compared to
wavelength of radio wave.
· A radio wave that meets an obstacle has a natural tendency to bend around the
obstacle. The bending, called diffraction, results in a change of direction of part of
the wave energy from the normal line-of-sight path. This change makes it possible to
receive energy around the edges of an obstacle.
· The ratio of the signal strengths without and with the obstacle is referred to as the
diffraction loss. The diffraction loss is affected by the path geometry and the
frequency of operation. The signal strength will fall by 6 dB as the receiver
approaches the shadow boundary, but before it enters into the shadow region.
· Deep in the shadow of an obstacle, the diffraction loss increases with
10*log(frequency). So, if double the frequency, deep in the shadow of an obstacle
the loss will increase by 3 dB. This establishes a general truth, namely that radio
waves of longer wavelength will penetrate more deeply into the shadow of an
obstacle
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Multipath in radio Communication

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Multipath
· Multipath is a term used to describe the multiple paths a radio wave may follow
between transmitter and receiver. Such propagation paths include the ground wave,
ionospheric refraction, reradiation by the ionospheric layers, reflection from the
Earth's surface or from more than one ionospheric layer, etc.
· If the two signals reach the receiver in-phase (both signals are at the same point in
the wave cycle when they reach the receiver), then the signal is amplified. This is
known as an “upfade.” If the two waves reach the receiver out-of-phase (the two
signals are at opposite points in the wave cycle when they reach the receiver), they
weaken the overall received signal. If the two waves are 180º apart when they reach
the receiver, they can completely cancel each other out so that a radio does not
receive a signal at all. A location where a signal is canceled out by multipath is called
a “null” or “downfade.”

· If the reflecting surfaces that cause the multipath situation do not move, the locations
of the maxima and minima will not move, hence the name ‘standing wave’.
· The depth of the null in a standing wave pattern is dependent upon the magnitude of
the reflection coefficient of any reflecting surface.

· The Effects of Multipath Propagation
o Multiple copies of a signal may arrive at different phases
o If phases add destructively, the signal level relative to noise declines, making
detection more difficult.
o Dealy Spread resulting in Intersymbol interference (ISI) - one or more delayed
copies of a pulse may arrive at the same time as the primary pulse for a
subsequent bit
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Fading and its types

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Fading::
· There is a large dependence of fading on distance.
o The probability of a fade of a particular depth increases with the cube of
distance. Thus, as the distance is doubled, the probability of a particular fade
depth increases by a factor of eight. Or, alternatively, the fade for a given
probability increases by 9 dB. So, doubling the distance will increase the freespace
loss by 6 dB, and increase the probability of fading by 9 dB, thus
increasing the overall link-budget loss by 15 dB.
· There is a slight dependence of fading on frequency. Increasing the frequency by
1GHz will decrease the probability of a fade by a factor of 1.08.
· There is a fairly strong dependence of fading on the height of the path above sea
level.
o There is simply less atmosphere at higher altitudes and therefore the effect of
atmospheric fading is smaller.
o For every 1000 meter increase in altitude the required fade margin reduces by
10 dB.
· Types of Fading
o Fast fading - occurs when the coherence time of the channel is small relative
to the delay constraint of the channel. Fast fading causes rapid fluctuations in
phase and amplitude of a signal if a transmitter or receiver is moving or there
are changes in the radio environment (e.g. car passing by). If a transmitter or
receiver is moving, the fluctuations occur within a few wave lengths. Because
of its short distance fast fading is considered as small-scale fading.
o Slow fading - arises when the coherence time of the channel is large relative to
the delay constraint of the channel. Slow fading occurs due to the geometry of
the path profile. This leads to the situation in which the signal gradually gets
weaker or stronger.
o Flat fading – occurs when the coherence bandwidth of the channel is larger
than the bandwidth of the signal.
o Selective fading – occurs when the coherence bandwidth of the channel is
smaller than the bandwidth of the signal.
o Rayleigh fading - assume that the magnitude of a signal that has passed
through a communications channel will vary randomly.
o Ricean fading - occurs when one of the paths, typically a line of sight signal, is
much stronger than the others.
o Nakagami fading - occurs for multipath scattering with relatively larger timedelay
spreads, with different clusters of reflected waves.
o Weibull fading - considers a signal composed of clusters of one multipath
wave, each propagating in a non-homogeneous environment.
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Diversity Techniques

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Diversity Techniques::
Fade margin on the transmitter path is not an efficient solution at all, and one alternate
solution is to take the advantage of the statistical behavior of the fading channel.
This is the basic concept of Diversity, where two or more inputs at the receiver are used
to get uncorrelated signals.

· Frequency Diversity
o Different frequencies means different wavelengths. The hope when using
frequency diversity is that the same physical multipath routes will not produce
simultaneous deep fades at two separate wavelengths.

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blackberry z10 vs lumia 920 vs iphone 5 vs rivals

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blackberry z10 vs lumia 920 vs Iphone 5 vs rivals

finally here it comes.....

one table to rule them all..features,specs....and much more :)

so go ahead ...watch,buy and enjoy your life




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History of Electronics Timeline

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DATE INVENTION/DISCOVERY DISCOVERER(S)


1745     Capacitor Leyden

1780     Galvanic action Galvani


1800     Dry cell Volta

1808     Atomic theory Dalton

1812     Cable insulation Sommering and Schilling

1820     Electromagnetism Oersted
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