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HD Quality between HDTV Antenna Digital Cable Satellite and Fiber Optic TV
You might be wondering if there is any difference in the picture quality depending on the source.
First, let me qualify my answer by telling you that I was one of the system integrators of digital cable back in the mid 1990's at General Instrument which is now known as Motorola Broadband.
The simple answer is there is no difference because the signal is digital, but let me qualify this further so you fully understand why you might see problems with the sources.
High Definition signals are broadcast in digital as opposed to television signals of the past which were broadcast in analog.
Because these signals are digital, they are not degraded by factors such as "path loss", which would be the signal strength degrading as it travels through the air (in the case of HDTV antenna) or over a cable (in the case of HD cable).
Further more, these digital signals have error correction which will correct for some of the loses in data which might result in something like a bird flying in front of your satellite dish (as in the case of DirecTV or Dish Network) or some interference with your HDTV antenna, such as someone walking through the room.
But for all of these transmission methods (HDTV Antenna, Digital Cable, Satellite or Fiber optic TV) to work properly, they need a minimum signal level and a minimum signal to noise ratio.
Many of you have probably experienced a high noise ratio on analog television. With digital sources you would most likely never notice this effect unless you have access to the error correction information and know how many bits are being corrected for.
When this low signal or high noise becomes severe with a digital signal, either one of two effects will be noticed:
1) Macro blocking - which are green squares appearing on the video
2) Total signal loss
The actual difference in the transmission method is in it's susceptibility to signal degradation (deterioration due to several factors described below):
HDTV Antenna - factors that can affect the digital signal
1) Distance (path loss causing signal level to be very low)
2) Location (high mountains, large metal buildings, etc)
3) High noise interference (such as lightning, bad weather)
Digital Cable - factors that can affect the digital signal
1) Bad amplifiers (in the cable system or even in your home if you use a signal booster - a caution on that below)
2) Bad connectors
3) Bad coax cable
Satellite (Dish Network, DirecTV) - factors that can affect the digital signal
1) Distance (path loss causing signal level to be very low)
2) Location (Trees, satellite low on the horizon, time of year, high mountains, other structures in the path, etc).
3) High noise interference (such as lightning, rain, snow, planes flying in the signal path)
4) Snow on your dish will cause signal loss.
5) Moving the dishes direction. The satellite dish needs to be accurately aimed at the satellite and have a clear line of sight (no obstructions in it's path).
Fiber optic TV - factors that can affect the digital signal
1) Cable or amplifiers in your home
There is not a lot because the digital signal is transmitted via a laser through a fiber optic cable and is not subject to interferences that can cause high noise or signal loses.
If you use a signal booster (amplifier) on your digital cable you could over possibly over amplify the signal and cause it to distort, which will cause high bit rate errors for your digital cable signal and will cause a large number of data packets to be lost because they can't be corrected for. This can either cause macro blocking (the green blocks on your picture) or total signal lose.
The same is true for using an amplified HDTV antenna or using an external amplifier with your HDTV antenna.
Also See: All High Definition Television Articles
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