Analog VS Digital Tuners and HDTV

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alexBB

New Member
#21
They are broadcast at the same frequencies as the current analog signals

This cannot be true from the standpoint of simple physics. Digital must be at least ten times the frequency of the analogue. In other words it should be at least an order of magnitude in a higher frequency range. Look at the distribution of TV channels. Digital are all high numbers and analogue (old format) is in the lower range, like 1,2,3,4, etc.

Tell me if you can get HDTV National Geographic channel on a dipole antenna? The channel that on my dial is 206 I believe? Or Palladia which is 208? I would like to see that.

You may be a TV repairman but I studies physics in depth and I know that the frequencies do not evren overlap. I am afraid you are confusing something. Aerial broadcast of digital signal to consumers is wastful. It is done thru cable ONLY. When you broadcast to consumers you have to cover a wide angle, essentially the whole 360 degree universe. Only a few antennas will catch the signal. 99.9999% of broadcast energy will be wasted.

The digital signal is broadcast thru air via satellites. It is a different business. Parabollic antennas are amplifiers for this week signal. Digital is also broadcast directionally between two high rise towers but it is a beam. Very little is wasted.
 
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5

54regcab

New Member
#22
HDTV National Geographic channel is through Pay TV only, they do not broadcast it.

Do you live in the USA? If you do you should know they are already broadcasting the major networks OTA on the same frequencies range for analog broadcasting. The system WORKS, plain and simple.

What is true of digital signal being "wasted" is also true of analog. Most of the analog signal is never received either. I never said it was efficient for a TV station to broadcast using towers that consumed several hundred KWH to be picked up by antennas at the micro volt level, but suck is the nature of any over the air broadcast including AM and FM radio.
 
DanceMan

DanceMan

Procrastinating Member
#23
54regcab

Appreciate the headsup on the analog antennas. Many years ago I used a very large FM antenna in my attic to pick up a 50-watt university station. Now I live on a hill and that info may be useful yet.
 
A

alexBB

New Member
#25
Do you live in the USA? If you do you should know they are already broadcasting the major networks OTA on the same frequencies range for analog broadcasting.

Yes, Midwest. I don't know what OTA is. I am not in hardware of any sort. My confidence in discussing the matter comes from my background in physics.

What are the ranges you are talking about? Give me the frequency range and I'll try to verify that thu my sources.

From the physical standpoint it is impossible to imagine that digital can be broadcast in the same frequency range.

Let's consider the physics. TV signals are all frequecy modulated. You have a carrier frequency and the encoding is done by changing this base frequecy to lower and higher frequencies according, let say, a cosine harmonic of 1000 Hz which is in the middle of spoken speech. In fact we have a mix of various harmonics ranging from about 50 Hz to roughly 20,000 Hz which is already beyond most people could hear. So, you need roughly 20Kz frequency range to transmit yuour signal and the base frequency is perhaps 100MHz. It is off the top of my head actually. I don't remember the actual figures. So, you need between 99,990Mhz and 100,010 Mhz to carry your signal just to cover sound track. Plus you need your video signal which requires much broader range because it is all pulses of high frequency.

The video signal which is all pulses is also coded the same miserable way: by harmonically changing the base frequency to lower and higher range but it needs a much broader range.

Now, in digital broadcast the sound signal is first fragmented into samples. Sampling takes place. You transmit digial code. You need to compress close to 16 pulses during the same time interval you transmit a small fraction of your cosine signal with the analogue. You will do the same thing eventaully: stretch and compress the base frequency but you will need a much broader range already for the sound track, perhaps 16 or 100 times that much. Therefor the digial signal goes into Ghz area. With digial the sampling of video is also improved, more pixels per square inch is taken, synchronization codes are slipped into the signal, etc, etc, etc. You cannot transmit high quality digital in the same range as analoue, no way.

Now, the higher the frequency the higher the loss of the signal thru the air. There are many capacitors on the way. The earth, buildings, etc. Energy sinks into those knots. This is why the preferred way to transmit digital is via a copper core or better laser fiberglass cable. The energy in this case goes forward as a narrow beam. This is the future.
 
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54regcab

New Member
#26
Theory or no theory, the frequencies actually being used are in the same range as analog. It WORKS, the exisiting tuners are picking up the digital signal on the same frequency range as the current analog transmission.

Pop over to www.antennaweb.org and see what you local channels are broadcasting on.
 
A

alexBB

New Member
#27
In one month, hopefully, this whole argument will be a moot point. No analogue will be used in the United States. As far as your site is concerned, I checked, found that I would have to sign on to look into it and backed off. Why in the world do I have to do it. Give me a solid data that I am wrong. Until you've done it I will maintain you simply do not understand what you are talking about.
 
D

Dawn McGatney

New Member
#29
***I don't know what OTA is.

Over The Air.

***From the physical standpoint it is impossible to imagine that digital can be broadcast in the same frequency range.

Analog and digital TV are both broadcast on the same frequencies.

***TV signals are all frequecy modulated.

No. Analog sound is FM. Analog video is VSB, a form of AM. And analog
color is analog QAM (Phase + AM). Digital video, sound, and data is 8-VSB
modulated, not FM. (FM is inherently analog modulation.)

***The video signal which is all pulses is also coded the same miserable way: by harmonically changing the base frequency to lower and higher range but it needs a much broader range.

Both analog and digital are broadcast in 6 MHz channels in the US.

***Therefor the digial signal goes into Ghz area.

No commercial TV, analog or digital, is broadcst in the US in the GHz
region.

***You cannot transmit high quality digital in the same range as analoue, no way.

It works.
 
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