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Old 10-13-2010, 02:26 PM
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DaveInDenver DaveInDenver is offline
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Quote:
Originally Posted by Hulk
Do you need less signal strength with digital or is the same strength needed?
Digital TV is obviously a digital mode. Think back to your ham knowledge, what is a primary advantage of digital modes, such as CW (Morse), PSK31, etc.? Higher signal to noise ratio. So yes, digital TV reception can tolerate a more marginal signal and still get an acceptable picture. The old U.S. standard was NTSC, which is essentially a multiple signal AM mode.

The need for a lower signal strength works in favor of the broadcaster, too. They might be using lower power transmitters now so that an individual TV that had an OK picture before will still have an OK signal now. When you are talking about replacing a 500 KW xmitter with a 100 KW, that's a major savings in electricity. If that means a typical TV used to need -20dBm to get a good picture and can now deal with -35dBm, they'll be happy to lower their power.
Quote:
Originally Posted by Uncle Ben View Post
Digital signals are short compared to the old analog signals.
Digital TV broadcasts still reside in the VHF-low, VHF-high and UHF bands. Most of the channels that were in the VHF-low have moved to VHF-high and UHF, so you don't need the super big antennas anymore. The bulk of TV here in Denver now sits at about 174-215 MHz and 470-650MHz. A dipole with length of about 31.44" and 12" is about right for Denver.

http://en.wikipedia.org/wiki/North_A...on_frequencies

The reason for the FCC push to ATSC was that each channel can take up less bandwidth now and so some of the old analog spectrum has been reallocated. But the channel centers haven't all moved to UHF and so most of the same propagation limits still exist like before.
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