Analog & digital

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Face
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Analog & digital

Post by Face » Tue Apr 06, 2010 5:14 pm

What is the deference between Analog data & Digital data.??

*Analog signals cover a range & Digital signals discreet values.?? Is this statement correct?

In the past we had Fm tuners with a range value. ex- 88.0 to 108.0 range.we can rotate the tuner and stop the meter in any place we want...
But now we have digital display FM tuners.It contain values between 88.0 to 108.0 ex-we can see meter goes 88.0>88.2>88.3......108.0 we can;t stop the meter like any place like old ones.we can use only the given values.
Is old FM tuner Analog & new one is Digital?is this correct...can we apply the Analog & digital theory for this FM tuner..or is this a bullshit question?.. ;)
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Re: Analog & digital

Post by Neo » Tue Apr 06, 2010 7:01 pm

Lets avoid some confusions here.
AnDi.png
AnDi.png (7.62 KiB) Viewed 10890 times
  • Ash coloured line represents an analogue signal
  • Red coloured line represents a digital signal
Refer this image for following two parts.
What is the deference between Analogue data & Digital data.??
Analogue data represented in a continuous form, as contrasted with digital data having discrete values.
Here the analogue data is the wave represented by ash colour whereas the digital data set is {0, 4, 5, 4, 3....}.
*Analogue signals cover a range & Digital signals discreet values.?? Is this statement correct?
Analogue signals are continuous in time and level. Digital signals are continuous in time but discrete in level.
In the past we had Fm tuners with a range value. ex- 88.0 to 108.0 range.we can rotate the tuner and stop the meter in any place we want...
But now we have digital display FM tuners.It contain values between 88.0 to 108.0 ex-we can see meter goes 88.0>88.2>88.3......108.0 we can;t stop the meter like any place like old ones.we can use only the given values.
Is old FM tuner Analogue & new one is Digital?is this correct...can we apply the Analogue & digital theory for this FM tuner..or is this a bullshit question?.. ;)
First lets clarify the modulation techniques in radio transmission. Mainly we have Analogue and digital modulation.

Analogue modulation methods
Amfm.gif
Amfm.gif (284.89 KiB) Viewed 10890 times
In analogue modulation, the modulation is applied continuously in response to the analogue information signal.

A low-frequency message signal (top) may be carried by an AM or FM radio wave.

Common analogue modulation techniques are:
  1. Amplitude modulation (AM) (here the amplitude of the carrier signal is varied in accordance to the instantaneous amplitude of the modulating signal)
    • Double-sideband modulation (DSB)
      • Double-sideband modulation with unsuppressed carrier (DSB-WC) (used on the AM radio broadcasting band)
      • Double-sideband suppressed-carrier transmission (DSB-SC)
      • Double-sideband reduced carrier transmission (DSB-RC)
    • Single-sideband modulation (SSB, or SSB-AM),
      • SSB with carrier (SSB-WC)
      • SSB suppressed carrier modulation (SSB-SC)
    • Vestigial sideband modulation (VSB, or VSB-AM)
    • Quadrature amplitude modulation (QAM)
  2. Angle modulation
    • Frequency modulation (FM) (here the frequency of the carrier signal is varied in accordance to the instantaneous frequency of the modulating signal)
    • Phase modulation (PM) (here the phase shift of the carrier signal is varied in accordance to the instantaneous phase shift of the modulating signal)
Digital modulation methods
In digital modulation, an analogue carrier signal is modulated by a digital bit stream. Digital modulation methods can be considered as digital-to-analogue conversion, and the corresponding demodulation or detection as analogue-to-digital conversion. The changes in the carrier signal are chosen from a finite number of M alternative symbols (the modulation alphabet).

A simple example: A telephone line is designed for transferring audible sounds, for example tones, and not digital bits (zeros and ones). Computers may however communicate over a telephone line by means of modems, which are representing the digital bits by tones, called symbols. If there are four alternative symbols (corresponding to a musical instrument that can generate four different tones, one at a time), the first symbol may represent the bit sequence 00, the second 01, the third 10 and the fourth 11. If the modem plays a melody consisting of 1000 tones per second, the symbol rate is 1000 symbols/second, or baud. Since each tone represents a message consisting of two digital bits in this example, the bit rate is twice the symbol rate, i.e. 2000 bits per second.

According to one definition of digital signal, the modulated signal is a digital signal, and according to another definition, the modulation is a form of digital-to-analogue conversion. Most textbooks would consider digital modulation schemes as a form of digital transmission, synonymous to data transmission; very few would consider it as analogue transmission.

Fundamental digital modulation methods
These are the most fundamental digital modulation techniques:
  • In the case of PSK, a finite number of phases are used.
  • In the case of FSK, a finite number of frequencies are used.
  • In the case of ASK, a finite number of amplitudes are used.
  • In the case of QAM, a finite number of at least two phases, and at least two amplitudes are used.
So, now you are clear both AM and FM are two techniques in analogue modulation.

So it is just the electronic metre that doesn't let you fine tune as with tuning condensers. However 0.05 variance is enough for FM band I think.
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Re: Analog & digital

Post by Face » Tue Apr 06, 2010 7:29 pm

thank BRO i got the idea.!!!!
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Story behind digital tuning ..........

Post by Magneto » Thu Apr 08, 2010 11:14 am

Dear Friend ,

You can not make tuning part in digital domain. It is pure analog domain work. In the Antenna wire , you can have all
the channels with very low sound level. That is induced , because of electro magnetic induction.

You can make a radio with long antenna wire and good ear phone and without any battery. this is the simplest radio in the
world. you can here all the channels like , but mixing up all the channel voices.

So in tuning stage , we are increase the amplitude of the channel what we want. Then we can here that channel loud ,
compare to other channel. Let say we want to tune our radio to 108.8 MHz. So we have to make 108.8 MHz in our radio.
So then because of resonance principal , automatically increase the amplitude of electromagnetic waves only which have 108.8 MHz , which induced in the antenna wire . But not increase the amplitude of other induced frequencies.
Because of this amplitude increase , you can here the channel which transmit in 108.8 in more clear and loud .

This is the basic principal behind tuning a radio and the main component behind this tuning circuit is oscillator circuit,
which is pure analog circuit. By changing the Resistance , inductance or capacitance of this oscillator circuit , we can
have different frequencies which are equal to our Radio channels. As example in normal radio , when you are tuning , you change the capacitance of a variable capacitor and then oscillator circuit make difference frequencies.

So what is digital tuning ?

So according to above discussion , you can understand tuning can not done in digital domain. So in digital tuning in
modern radio setups , we obtain a variable voltage from Digital to Analog converter . So when we press a button , it issue signals to this Digital to Analog convert to change it's digital value and hence change the output analog voltage.
So we are feeding this variable analog voltage into a vericap diode. The basic feature of a vericap diode is , it can
change it's capacitance according to the voltage applied. so in this way we obtain a variable capacitance for our oscillator
circuit and then oscillator circuit obtain a variable frequency according to that.

So you have to clearly understand that in digital tuning , we only issue control signals from digital circuit to oscillator circuit , which is pure analog circuit.
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Re: Analog & digital

Post by Face » Fri Apr 09, 2010 5:47 pm

You can make a radio with long antenna wire and good ear phone and without any battery.
this is the most interesting sentence of the post.....

can you explain more about this...??friend......
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Re: Analog & digital

Post by Magneto » Fri Apr 09, 2010 6:14 pm

Dear Friend ,

You can make the simplest Radio in the world , from just a twin wire and with a good ear phone.

Here having a good ear phone should be important to here sufficiently high sound. Ear phones , which are using in
telephone receivers are ideal for this. And you want to find a long twin cable (two wires twisted together). PVC twin cables ( brown and red or
brown and blue) which are taking for electrical wiring is ideal for this and these are available in any hardware.

The length of the wire should be about the distance of your TV antenna to ground. So remove the plastic shield in
both ends of the twin wire and fix one end to some long height. You can use your TV Antenna pole for this. and connect
the other end to the ear phone.

So now you can here some voice, which is a mixture of all the channels. Longer the height of the cable , you can here
better voice. And also the area should be a open area for here good sound.

So this is the simplest Radio in the world :D

The theory behind this is when you have a large long wire , amplitude of the electromagnetic signals induced in it is sufficiently high. So they have sufficient strength to vibrate the ear phone , with out using any electronic amplifier.
As a result you can here some sound. As here tuning stage is not available , all the sounds are hear with mixing up.

This is rainy season , so be careful when you climb to fix the wire :D

Good Luck !!
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Re: Analog & digital

Post by Face » Sun May 09, 2010 7:47 pm

I tried on this...I could get some little sound out....can't identify it that sound.But really happy in practical work.This was my first one in practical work..(coz I am a lazy person who love only reading) :mrgreen: :mrgreen:

Thank you Magneto

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Re: Analog & digital

Post by Mysoogal » Mon Nov 15, 2010 11:50 pm

i really hate samsung TV with has built in digital TV, the problem is picture Q can be blocky sometimes, when i had old type of TV which was not digital, i could change channels really fast and rarely see artifacts on the TV in the same point where new TV is. i think digital TV is like pop up banners on the INTERNET just think how much garbage they can push through the digital set box now :(

all hail to analog :lol: long live analog TV
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