Article: Diginets come of age

Discussion in 'Over the Air TV By RabbitEars.Info' started by comfortably_numb, Dec 12, 2018.

  1. dhett

    dhett SatelliteGuys Family

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    I'm afraid that I fail to see your point, or the relevance of the UHF TV band (old: 228 MHz [includes ch. 37], new: 138 MHz) being wider than the VHF TV band (lo: 34 MHz [includes the 4 MHz between chs. 4 and 5], hi: 42 MHz). It doesn't change the fact that no primary-rights (i.e., full power and Class A) TV station was forced to change bands; all band changes were voluntary and compensated.

    Again, all operational secondary-rights (i.e., LPTV and translator) TV stations were given a window in April and May to request their displacement channel reassignment. Nationwide, there were only 90 instances of mutually exclusive requests for displacement channels, five of which involved Oregon stations, and only one of which was in the crowded Portland metro area, involving two stations both requesting ch 23. But even in the Portland metro, there are still enough channels available so that every UHF secondary-rights station can still end up with a new UHF channel. In fact, KGWZ-LD is staying with ch 23, and KEVE-LD is now requesting ch 31, so that one is already resolved as of 11/29/18. There is no reason to believe that the Willamette Valley will be a problem.
     
  2. harshness

    harshness SatelliteGuys Master

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    You're talking about bandwidth useage and I'm talking about receive antennas. It is no wonder you're missing the point.
    Does your analysis contemplate translators?
     
  3. dhett

    dhett SatelliteGuys Family

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    I fail to see the relevance of your point, and you fail to explain yourself. All you've posted is technical-sounding gibberish. Again, mobile TV worked just fine in the analog days, even for lo-VHF, and I'm not talking about limousine setups either.

    Yes.
     
  4. harshness

    harshness SatelliteGuys Master

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    One person's technical gibberish is another trying to get a point across to someone who apparently doesn't understand basic terminology and physics behind OTA TV antenna theory.

    When the term "mobile" is used, I think most have jumped to the conclusion that this meant receiving TV on phones and tablets with suitable receivers attached (and eventually built in). From there, I've noodled the size of the antenna required and determined that something that attaches to a phone (especially now that some phones don't have headphone jacks) isn't going to be sufficient to receive TV stations in the same way that the old portable TVs had whips or rabbit ears.

    To answer my challenge, you need to cite evidence that mobile devices (phones, tablets, notebooks, handheld TVs) will be able to be fitted with antennas that will allow them to pick up TV frequencies (not just a high UHF demo like they did in Las Vegas).

    Some early claims about what ATSC 3.0 would bring to devices:

    ATSC 3.0 will change watching TV on mobiles

    ATSC 3.0 chips in the iPhone and other smartphones? Don’t hold your breath | FierceVideo
     
  5. dhett

    dhett SatelliteGuys Family

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    OK - now we're getting somewhere. Thank you for clarifying.

    You are correct: my examples were portable TVs with telescoping antennas, or even a phone I had that had an extensible antenna built in.

    Let's address the antenna. The antenna measurements commonly cited are for optimal reception. For a UHF station, antennas don't need to be so large, as the wavelength of the signal is quite small. For a VHF-hi station, a dipole antenna needs to be anywhere from 26.4" for RF ch 13 to 31.8" for RF ch 7. For VHF-lo, the dipole needs to be quite long - from 66" for RF ch 6 to 98.6" for RF ch 2. The truth is, you didn't need an antenna that large for decent reception in NTSC analog and you don't need an antenna that large for ATSC 1.0 8-VSB modulation. Unfortunately, I don't have any VHF-lo stations in my area, but it's been a common saying that if your signal is strong enough, you could pick it up with a paper clip. Certainly, that is not the optimal antenna, but I did a little experiment. I took a 6" paper clip and plugged it into my ATSC 1.0 tuner dongle (see PaperClipAntenna.jpg).

    Hardly the most optimal antenna. Yet I was getting a serviceable signal on KAET RF ch 8 (see KAET.png)

    That's right, on high VHF. That wasn't supposed to happen. Here's low power Class A station KAZT on RF ch 36 (see KAZT.png).

    A 6" antenna can easily be miniaturized using a fractal antenna, so it's not hard to conceptualize putting a receiver into a cell phone or tablet.

    The next item to address is the fact that OFDM-based ATSC 3.0 will be much more forgiving of a less-than-optimal signal than 8-VSB-based ASTC 1.0 is. That's the difference and a major benefit that ATSC 3.0 offers. Will that help for VHF-lo? I don't know - I don't have a VHF-lo station nearby to sample - but don't overestimate the reach of VHF-lo stations. Very few of them exist, even after the repack.
     

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  6. harshness

    harshness SatelliteGuys Master

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    You left out a couple of key metrics in your analysis: distance from the station and barriers to propagation (or lack thereof as I suspect is the situation where you are). Most of my TV stations are about 50alm away (as are most of my FM radio stations). I happen to have LoS to most of them but anything less than a good set of rabbit ears wouldn't get me the analog stations back in the day. If the TV was moved or even turned, the rabbit ears would have to be adjusted.

    I have a 60 mile antenna now and it does great but I have to point it within a few degrees of the towers or the signal is trash. I understand antenna loading and fractals, but there is a limit on how low they can practically go. I firmly believe that the whole "mobile TV" thing has been grossly oversold as it applies to viewers outside the major metropolitan areas.
     
  7. dhett

    dhett SatelliteGuys Family

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    I can tell you that at that distance, mobile will not be likely. I don't know where you've been reading, but I've never seen mobile sold as available from great distances. In fact, it's well-known that signal propagation is one of the areas where 8-VSB modulation outperforms OFDM, and a major reason why the FCC went with 8-VSB 20 years ago, when Sinclair was pushing for COFDM. When ATSC 3.0 becomes a reality, look for a wave of stations requesting power increases, and the FCC revisiting their power limits.

    Although I have a favorable location for OTA, my readings were taken from indoors. With a stucco house, the chicken wire on the outside walls that hold the stucco in place also attenuates the signals somewhat. Mobile viewing will always be subject to those limitations, regardless of modulation. It will remain to be seen how forgiving ATSC 3.0 is; what we do know is that ATSC 1.0 is completely unforgiving. I can't imagine it getting any worse.

    What I did show is that it doesn't necessarily require rabbit ears to receive hi-VHF, especially the full-power stations. And UHF should be a slam dunk. Although it was a 15 kW signal on RF ch 36, there is also a co-channel station in Tucson, 100 miles away. I can't say how lo-VHF will perform, as the closest LPTV station to me is 100 miles away in Tucson, and the closest full power station is 300 miles away in Las Vegas, and those are ATSC 1.0 stations.

    Well, congratulations! It looks like you and I have completely hijacked this thread, so I'm going to try to tie back to the topic by saying that if ATSC 3.0 lives up to what we know is true - and not the hype - we could see more and more diginets coming. Word is that the broadcast networks and station owners are more likely to air additional content at up to 1080p, rather than dedicating the channels to 4K content, so there will be more room for new diginets. Weigel and Katz both seem committed to producing new diginetss, and I've fairly impressed with the alliances with major networks that they've been able to forge. I am disappointed that Weigel seems to abandon the old ones, such as ThisTV, in favor of the newest shiny keys, but at the same time, I'm glad to see that the new diginets are more than just rehashes of TV Land.
     
  8. harshness

    harshness SatelliteGuys Master

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    I'm not sure we've established that there's a need to broadcast some of this content to more than a relative handful of viewers and broadcast probably isn't the most efficient way to do that. Using broadcast to index IP-delivered content seems like a horrible waste of resources.

    More isn't always better or even desirable other than to those who live to count channels.

    There seems to be less and less interesting content on the cable channels and I don't see how making content available free OTA is going to improve that. In the grand scheme, it doesn't really open up access to a significant number of new eyeballs and the funding model is already floundering for OTA.
     

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