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Roamio for cord cutters?

Discussion in 'TiVo Roamio DVRs' started by barmer, Sep 21, 2018.

  1. barmer

    barmer New Member

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    I've invested a lot in my Roamio + minis. I'm about to get fiber internet and would love to dump Comcast while still using the Tivo hardware for TV. I assume I'm limited to the Tivo apps. Has anyone done this, and which streaming app do you recommend? Hulu? Does the Tivo app support Hulu's Live TV?
     
  2. krkaufman

    krkaufman TDL shepherd

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  3. krkaufman

    krkaufman TDL shepherd

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    What model Roamio do you have, a 4-tuner? Or a 6-tuner Roamio Plus or Pro?

    A 4-tuner Roamio would allow you to switch to recording from an Over-the-Air (OTA) antenna.
     
  4. barmer

    barmer New Member

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    Bummer about Hulu.... I thought that would be my primary option. I wish Tivo would expand their App ecosystem, but I know their next gen platform will be focused around this use case so guess I'm not surprised from the lack of new apps.

    My Roamio is 4 tuner. Good suggestion, but OTA at my house is challenging. I'm between major cities so I don't really get good signals from either unfortunately.
     
  5. gigaquad

    gigaquad Tivo Image Master

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    Grab one or two of these and connect them in your attic
    https://www.amazon.com/gp/product/B004NQMCDK/

    I'm about 30 miles from town and it picks up mine just great. Your tivo has a strength meter built into it that lets you tell what the best position is.
    Welcome to the dark side :)
     
  6. krkaufman

    krkaufman TDL shepherd

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  7. barmer

    barmer New Member

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    Thanks to you both! Looks like I have enough signal after all for the channels I care about. Some green and only Fox in the yellow.
    However, your "get one or two" confuses me. How could you have 2 antennas feed into Tivo?
     
    krkaufman likes this.
  8. mdavej

    mdavej Well-Known Member

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    I use 2 antennas in my location because I have one channel that's in the opposite direction from all my other channels. I join them in the attic with a splitter in reverse. But the section of coax from the splitter to each antenna must be exactly the same length. If you do it right, it works fine.

    I gave the exact same antenna in the link to my parents. Works great except for the rotator. It's impossible to precisely control. So I just aimed once and never rotate again. I personally use a different antenna that's a little larger, due to my location. My second antenna is a pennyloop I made out of coat hangers.
     
    dfreybur likes this.
  9. snerd

    snerd Active Member

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    I'm quite skeptical about the requirement for equal length coax, especially when the antennae are pointing in different directions. Do you have a reference for that?

    Even more skeptical if the antennae are physically very different. I'm guessing there may be some mythology in play here.
     
  10. JoeKustra

    JoeKustra in the other Alabama TCF Club

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    If you Google "coax length" you will get almost 8 million results. True, most are for lower frequencies, but stuff coming down that coax is still analog.
     
  11. mdavej

    mdavej Well-Known Member

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    Reference:
    TIP: Combine two antennas for even better reception - The Solid Signal Blog
    The potential phase difference from different lengths of cable makes perfect sense to me. But I agree that small differences in length are probably negligible.

    Keep in mind that when you combine 2 essentially identical signals, if one has to travel further than the other, it will be shifted in time (phase). So rather than the sum of the 2 simply increasing the amplitude as desired when in perfect phase, they would be a jumbled mess. The one that travels the furthest would be an echo essentially, having the same effect as multi-path from a reflected signal. In the old analog days, that resulted in ghosting. Not sure how digital TV handles that, but I'm sure it's not as good as no multi-path.

    Let's say, for example, I want to combine rabbit ears at my TV (1 meter) with my roof antenna (50 meters). Assume that both antennas receive the signal at the same time. The attic antenna signal arrives 0.16 microseconds later than the rabbit ears. For a typical 200 MHz signal, that's one cycle of the carrier every 0.005 microseconds. So the two signals are 32 cycles out of phase.

    If you think this is just BS, then you're welcome to join your antennas however you wish.
    I wouldn't Google that, rather "combine two antennas".
     
  12. snerd

    snerd Active Member

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    Totally agree that the signals are analog. As an RF engineer, I understand a great deal about the properties of coax, and how those properties vary from DC up through microwave frequencies.
     
  13. mdavej

    mdavej Well-Known Member

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    I'd love to be convinced the equal coax length is BS. One less thing I'd have to worry about. So what does the math say? I'm also an engineer and can probably follow it. 30 years ago I could derive Maxwell's equations, but I can't anymore, so try to keep it as simple as possible.

    EDIT: Looks like the cruz of the matter is how the equalizer on pg. 97 of the document below handles multipath. I'll have to digest it before I can discuss intelligently. I'll need to see if the conditions I laid out would have a significant impact or not.

    https://www.atsc.org/wp-content/uploads/2015/03/a_54a_with_corr_1.pdf
     
    Last edited: Sep 24, 2018
  14. dlfl

    dlfl Cranky old novice

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    The wavelength of channel 14 (473 MHz) in air is 0.63 meter. In coax it is roughly 2/3 of that, i.e., ~0.4 meter. Completely destructive interference (180 degree relative phase) occurs at 1/2 wavelength i.e., 0.314 M in air or 0.2 M in cable. For two signals (at the same frequency) to combine constructively the two path lengths must be equal within a small fraction of the half-wavelength (plus or minus multiples of the wavelength). If the signals are equal strength and the path lengths differ by a multiple of the wavelength plus 1/2 wavelength, destructive interference will cause them to cancel when combined. However, if one signal is much weaker than the other, the interference, whether destructive or constructive, won't make much difference.

    My conclusions:
    1. For combining two opposite facing, co-located, antennas with coaxes into a splitter or amp, the equal length rule is good, although really only important if the two antennas can pick up signals for the same channel with almost equal strengths.

    2. The rabbit ears and roof/attic antenna case is subject to the path differences from the broadcast tower to the antennas measured in half-wavelengths which, practically speaking, is unknown and random. Thus the equal length constraint is meaningless.

    The equal length rule is only meaningful if the two antennas receive a given channel frequency with approximately the same phase and with strengths that are not very different.
     
    snerd likes this.
  15. LarryAtHome

    LarryAtHome Member

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    To confuse things even more, if the antenna are mounted for both do not receive the signal at the same time, i.e. mounted in different places, will have the same effect as the 2 coaxes not being the same length as each signal will hit the splitter/combiner at different times. (phases) It really is a lot of trial and error.


    "My conclusions:
    1. For combining two opposite facing, co-located, antennas with coaxes into a splitter or amp"
    With a lot of antenna, unless you make a special bracket, they will not be co-located. (or at least the receiving elements)
     
    Last edited: Sep 24, 2018
  16. snerd

    snerd Active Member

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    Thanks for the reference.

    Phase differences certainly matter when you're using two antennae that receive from the same source. But if you have one pointing at towers 23 miles away and another pointing in a different direction at towers 37 miles away, the lengths of the coax segments are pretty much irrelevant.

    That analysis is fine when both antennae are receiving from the same source, and two antennae are working together to boost the signal. Two antennae pointing toward two different sources are mostly receiving two independent signals. That is why the coax length is irrelevant for the case that you're describing.

    Nitpick: the delay for 50 meters of RG6 will be more like 0.2 microseconds, since propagation is only 82% of the speed of light in free space.

    Phase differences that are too small to cause ghosting can still cause reception problems, since signals that are 180 degrees out of phase will diminish the signal rather than boost it. Using two antennae with vastly different physical construction makes it harder to get a perfect phase match, because every antenna will introduce some phase shift in the received signal, and the amount of phase shift will vary due to the specific physical construction. At 200MHz, the wavelength in RG6 is only about 4 ft,

    I agree that multipath issues aren't BS, but sending signals from rabbit ears through 50m of coax could be a "cure" that is worse than the disease.
     
  17. snerd

    snerd Active Member

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    Thanks for that link, interesting document. It sounds like the receiver has three different options for trying to cancel multipath effects.

    Have you tried your system both ways, with and without the extra coax for the homemade antenna? It seems to me that channels received by the rooftop antenna are unlikely to have issues, since it will be more directional and have more gain than the pennyloop, so that the main concern would be channels received by the pennyloop if the side lobes of the roof antenna pick up enough signal to cause problems.

    One problem with the equal coax length "solution", is that it only truly works if the two antennae are placed at the same location, which is physically impossible. Placing them on the same mast but pointing in different directions is good enough, but with one antenna on the roof and another inside the house, equal coax length will only be correct if the two antennae are on a line that is equidistant from the transmitter. The gotcha here is that when you are pointing the antenna at different towers, you can only be equidistant from both when the pennyloop antenna is placed at or near a point that lies directly below the roof antenna. With any other placement, the coax length needed to properly adjust the phase for optimal reception from the roof antenna will be different than the coax length needed to properly adjust the phase for optimal reception from the pennyloop antenna.
     
  18. mdavej

    mdavej Well-Known Member

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    Yeah, both antennas are in exactly the same location, with my pennyloop attached to the backside of my directional one on the same pole. So the loop will pick up all the same UHF stations as my directional PLUS the one station in the opposite direction that the directional cannot see. That's why I'm so concerned about phase shift.

    I have not tried unequal coax as it was easier to use equal, 12 inch lengths.
     
  19. Bigg

    Bigg Cord Cutter

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    As usual, the forum has way over-complicated things. For most people, in most markets, a single antenna is fine. If you have VHF stations, you'll need one that does VHF as well.

    That being said, ignore what apps the TiVo has or doesn't have. Whether you have cable or don't have cable, the best way to stream stuff is through a Roku, FireTV, or Apple TV. Pick whatever platform/ecosystem you like, and run with it. Use the TiVo for OTA broadcasts only and you'll be much happier with TiVo and much happier with your streaming experience. That's what I do with mine.
     
    A2JetGuy likes this.
  20. dfreybur

    dfreybur Active Member

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    If you are so far out in the woods that cable is your only choice, then just keep paying the $300 per month for cable. Or by now I guess it would be $350 - The bill went up some each month every month since cable first appeared in 1980 or so.

    UHD TVs now come with some sort of smarts built in. Just push the input button and switch remotes.

    That said I still use the apps on Tivo. If they get bad enough I'll drop Tivo. Some products like cars are on the market for a century. But not all products last that long.
     

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