How good is ATSC TV weak signal performance?

[KE7IZL]

I remember that with NTSC (analog) TV, you could sometimes pull in a weak station (like one from a city 50 miles away) if you played with your antenna, and got it positioned just right. How good is ATSC (digital) TV with this kind of thing? On one hand it seems like it might be better than analog, because with error-correction coding it can correct for errors introduced by the signal being "buried in the noise", making for a perfectly clean picture for a digital transmission, even if it would be noisy in an analog transmission. However, on the other hand, if there are too many errors, and the error correction can't fix them, it will then fail the CRC check, and the packet with the errors will get rejected entirely, unlike with analog where SOMETHING (however degraded it may be) is shown on the screen, no matter how weak the signal. So in the end, does ATSC work better or worse than NTSC for trying to see distant/weak stations? Anybody have any experience with this?

 

[slicerwizard]

ATSC is far better at weaker signal reception. By the time ATSC fails, an equivalent analog signal would be painful to watch - what little there was to see...

I use an indoor antenna to pick up signals that originate over 60 miles away, plus one or two transmitters that are about 100 miles distant, and the paths go through neighbouring buildings as well as some dirt, what with me living in a bit of a valley - but they're all usually crystal clear. Analog could never compete with that - there would be massive ghosting from multipath as well as the usual noise artifacts associated with weak analog TV signals.

 

[prcguy]

The carrier to noise ratio threshold for an ATSC receiver to lock and give a usable picture is about 15dB. An analog NTSC receiver with an amount of noise in the picture that most people would consider annoying but usable is about 34dB carrier to noise ratio and a perfect analog picture requires about 51dB carrier to noise ratio. That's a huge margin in favor of ATSC.
prcguy

 

[lmrtek]

RF is RF ATSC is just modulation on a carrier
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ATSC is easily wiped out by ghosting, co-channel, and narrow fm transmitters.
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The old analog receivers could still watch pictures with these same levels of interference.
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So while ATSC provides a great picture under good signal conditions, analog was far superior at operating with narrow fm interference, co-channel, and ghosting.
............

 

[KE7IZL]

The carrier to noise ratio threshold for an ATSC receiver to lock and give a usable picture is about 15dB. An analog NTSC receiver with an amount of noise in the picture that most people would consider annoying but usable is about 34dB carrier to noise ratio and a perfect analog picture requires about 51dB carrier to noise ratio. That's a huge margin in favor of ATSC.
prcguy

How weak would the s/n ratio need to be before the h-sync or v-sync would be lost, such that the picture would become distorted or start rolling?

 

[k9wkj]

i really have been astonsihed how well ATSC holds up
a friend of mine K1MOD who is now SK had some amazing grabs of ATSC
even before most folks had a receiver to watch it
here is a link to the wayback machine with a bunch of his grabs
https://web.archive.org/web/20120109034326/http://oldtvguides.com:80/all_DTVs/

and dont forget with the current DTV repack going on
we are getting a number of Low Band tv channels back
yes even a couple channel 2 stations !

 

[prcguy]

Are you asking about analog or digital? Digital would be very predictable and a 16dB carrier to noise should give a perfect picture where 14dB would loose everything. There is no H or V sync or picture rolling with digital.

Analog can get so noisy that its nearly unwatchable before any sync is lost. I think multipath distortion is more of a problem with sync loss and picture rolling on analog.

How weak would the s/n ratio need to be before the h-sync or v-sync would be lost, such that the picture would become distorted or start rolling?