Originally Posted by mtownsend (Post 12016)

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.

Originally Posted by be236 (Post 12023)

Yes, you're correct.. when I said signal of -5 dBm, I mean that's the NM value I get here in Tvfool when it shows channels for my specific location.

So back to my actual problem that I started for this thread.

The channels I want show up to -16 dB NM value. Then I need to find an antenna that is spec-ed/claimed to be +16 dB gain or higher , right so that I can get above the 0 dB threshold to get a signal lock?

That Lava antenna claims +30 dB gain (but not sure if they meant that is for the pre-amp gain and not the antenna gain itself).

The DB8 antenna I see in various sites show a gain of +16 dB, which would get me to this 0 dB threshold... but looks like I need more gain to get signal... would I have to string 2 DB8s together or something like that (would look unslightly)...

Originally Posted by rickcain (Post 12028)

What's frustrating is now legitimate sites like SolidSignal are starting to sell scam antennas, shame on them.

Originally Posted by GroundUrMast (Post 12031)

If the prediction is 100% accurate, and if there is never any fading, and if there is no interference, and if you have a perfect receiver, then reception of a signal with a NM of -16 dB would require an antenna that has 16 dB of gain on the channel of interest plus the additional gain needed to overcome the noise figure of any amplifier used. That equates to antenna gain of 19 dB in theory (assuming a preamp NF of 3 dB).

In the real world, a 10 dB 'fade' margin is cutting it quite close. Engineering for a margin of 15 dB is not overkill by any means (IMO). So I'm suggesting an antenna with 29 to 34 dB of forward gain. (I know of no such antenna on the consumer or commercial market.)

Reception of a signal arriving at a NM of -16 dB is going to be impossible in some cases, unreliable in others. In a few cases, you'll get lucky and find that the prediction was off in some way.

It may be more practical to find a friend in Bellingham or Lynden who would allow you to operate a HTPC or Slingbox remotely.

Originally Posted by be236 (Post 12034)

What's funny is that I can get CHEK 6 VHF analog and they show NM of -10 dB. Heheh...

As for that slingbox idea, yeah, I thought about that.. wonder why there's not a website that would do something like this? I guess it would be a copyright issue, huh?

Originally Posted by GroundUrMast (Post 12035)

I can still see a couple of analog Canadian stations here in Seattle. They're quite noisy (snowy). Analog kept working when the signal got weak. OTA DTV has quite a bit of forward error correction ability engineered into the ATSC standard so it looks perfect right up to the point where the receiver can no longer decode valid data. Digital signals are prone to that phenomenon, referred to as 'cliff effect' where, when close to the minimum, a slight decrease in signal to noise will produce a dramatic increase in error rate.

Originally Posted by be236 (Post 12034)

wonder why there's not a website that would do something like this?

Originally Posted by Tower Guy (Post 12078)

Bamboom http://bamboom.com/

http://arstechnica.com/tech-policy/n...n-new-york.ars

Originally Posted by GroundUrMast (Post 12077)

Using consumer grade (priced) equipment, you best hope for seeing any signals from Canada would be an Antennas Direct XG-91, their CPA-18 or CPA-19 preamp, mounted on a 5' tripod + 10' HD mast at the roof peak.

I would expect that you would see some signals, at least intermittently, weather and atmospheric conditions would often rule.

Mounting at eave height would likely rob you of precious signal.

(From Canada, I now see only CHEK-6)

Originally Posted by GroundUrMast (Post 12094)

Which mounting option is best... you'll need to try both to know for sure.

In the winter with all the leaves off the tree, I'll bet a cup of coffee on the shot through the tree.