Quote:
Originally Posted by mtownsend
Keep in mind that analog (NTSC) signals NEEDED much more power to achieve a clear picture. They need a fairly high signal to noise ratio (say roughly a 27 dB SNR) to produce a clean (like VHS tape quality) image.
Digital (ATSC) signals can produce a clean (like DVD quality) image while using less signal power (roughly a 15 dB SNR).
The lower power of digital broadcasts does not make it harder to receive. The power was reduced to maintain roughly the same amount of coverage as the old analog systems. Since the threshold for reception has been reduced, it takes less power to get to that threshold. The high ERPs with analog stations was mostly out of necessity due to the spectral inefficiency of that signal format (developed in the 1940s and 50s).
In general, ERP is a bad way to look at station effectiveness because it does not take into account the signal type (ATSC vs. NTSC) and it does not take into account the frequency (high frequency channels require much more power than low frequency channels). For example, a 50 kW digital station on channel 7 will cover the same area as (actually even more than) a 5000 kW analog station on channel 51.
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Ah, ok, got it... ATSC requires less power than NTSC...
And yes, I knew about VHF signals go further in distance than UHF, which is why I was disappointed to know that those Vancouver stations went from VHF to UHF.
For example, I was able to receive analog channels 6, 8, 10 ERPs like 200-300kW (fuzzy, but watchable) at 100 miles away with my current antenna system... now they are at UHF at 40Kw... So I am just disappointed that it will take another big antenna in any hope of receiving these signals.
But like I said in my earlier post, I had Artec DTV box and once in a while, I would see a "signal" blip in its signal meter on channel RF 22 (CHAN) at 100 miles and 40kw... and my location shows it is at -9.8 dB NM.
This gives me hope to pick up this channel somehow if the best GAIN UHF antenna (either DB8 or Clearstream 4?)