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Analog vs. Digital Transmission
by Gary Davis
Dish-Network-Satellite-TV.ws
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Remember the old days of analog TV, radio, etc. Most of us do
unless you’re really young. And still today there are plenty
of analog systems in use. Normal radio still uses analog transmission.
But the digital age has begun and more and more we will use
digital systems rather than analog systems.
Digital transmission systems have many advantages over analog
transmission systems, like higher quality of audio and video.
How come digital systems can transmit higher quality signals
than analog systems? The truth is that they don’t. They
just use some tricks to eliminate noise.
Analog Transmission Systems
When something like video and audio, is recorded by an analog
system, the recording has a certain quality. This recording
(when done professionally) has a very high quality. When the
recording is transmitted it is modulated directly to a carrier
wave, which is then transmitted through the air, cable, via
satellite, etc. During this transmission, the carrier and the
modulated signal will loose amplitude (power) and due to interference
noise is introduced to the carrier and its modulated signal.
The result will always be a received signal that has a lower
quality than the transmitted signal. Hence, the modulated signal,
the recording, will also be of lower quality than the original.
Analog transmission systems are unable to maintain the quality
the original has.
Digital Transmission Systems
In the digital world the recording can be transmitted to another
place without loosing any quality. An exact copy of the original
recording is transmitted. So how come that digital transmission
systems don’t loose quality when transmitting a signal?
Well..... Actually they do lose quality just like the analog
transmission system does.
Surprised? No Problem. Most people don’t know that digital
signals still need to be transmitted by analog transmission
systems. The trick is that a digital system doesn’t record
analog signals, but encodes analog signals into bits (zeros
and ones). A sample is taken many times per second and the size
of each sample is written down in bits. For instance a sample
with the value of 9 would be 1001 and 11 would be 1011.
The digital transmission system needs to transmit those zeros
and ones, and it does this by modulating the carrier wave. Low
power for a 0 and high power for a 1 (This is the most simple
way of modulating. There are much more sophisticated forms of
modulation, but it would take a whole book to describe them
all.)
So on the receiving end, it doesn’t matter anymore what
the quality of the signal is, as long as it still is possible
to identify the zeros and ones. Noise in the received signal
is no problem. A “1” with noise is still a “1”
and a “0” with noise is still a “0”. Of
course the noise can not be too high, otherwise mistakes would
be made and a zero would be received as one or a one would be
received as a zero.
So Digital Transmission Systems are better because they eliminate
the effect of noise completely. You don’t look and listen
to a received signal from an original recording, but you look
and listen to a reproduced signal of the recording. The reproduction
comes from an exact copy of the original recording.
The quality of what you see and hear now depends on your TV
and Sound System. A high quality TV and Sounds System will give
you high quality Video and Audio. The negative effects of the
(still analog) transmission have been eliminated from the process.
Satellite TV makes use of Digital Transmission Systems. What
you see at home will always be of Digital no (much less) noise
Quality.
About the Author
Gary Davis is owner of Dish Network Satellite TV, has several
years experience in the Satellite TV Industry and has written
several articles on satellite TV. |
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