Unable to pull in VHF Hi stations

Discussion in 'Over the Air TV By RabbitEars.Info' started by BDClark, Jun 14, 2019.

  1. BDClark

    BDClark Topic Starter Member

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    Hey folks, great learning resources in this forum and I thought I'd check in for some advice on what to do here. As you can see in my TV Fool report, the majority of our channels are UHF and they come in quite well. Unfortunately there are several channels & sub-channels co-located on the same tower broadcasting in VHF Hi that either aren't coming in at all or have two bars on our TCL TV. I've got a Mohu Air 60 I bought a few years ago (same as the Sky 60 more or less, just a renamed one for Best Buy) that's pulling in the UHF stuff and it's doing great, so long as you use the included amplifier (I get nothing without it).

    I saw a YouTube video stating you can get a splitter and run it in reverse to combine multiple antennas, so I picked up a GE 33685 yagi antenna from Walmart and I have them both connected on the mast that came with the Mohu. The Mohu is as high up on the mast as I can get it, and the GE is about a foot under it. With the splitter reversed and using the Mohu's amplifier, I'm still getting the same channels but nothing from the VHF stations. I used Winegard's aiming app to point the GE antenna, but no luck. There are some trees in the equation as well. I tried to attach an image, but the forum software didn't like that. Should I ditch the Mohu mount and buy some mast to get them up higher? In case the reversed splitter idea was incorrect, I've ordered a UHF/VHF diplexer from Antennas Direct through Amazon which should be here tomorrow. If you need any more information from me, just let me know.

    VHFPointing.png
     
  2. comfortably_numb

    comfortably_numb Dogs have owners, cats have staff Pub Member / Supporter

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    Good morning,

    Have you tried using the GE yagi by itself? Remove the splitters and diplexers and try it by itself. If you want to use a preamp with the GE, you need to purchase a separate one. I don't recommend trying to use the Mohu's amplifier to boost the GE yagi's signals.

    As the seasoned experts around this forum will be sure to tell you, combining 2 antennas is tricky business, and not always effective. It IS possible to combine a VHF-only antenna with a UHF antenna using a preamp with separate inputs, like this one. I have done that with some success.
     
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  3. waylew

    waylew SatelliteGuys Pro

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    Just a guess,but the amp in the mohu is likely uhf only and not doing a thing for vhf,except for trapping it out altogether.You'd need an amp with separate vhf and uhf inputs,such as the RCA TVPRAMP1Z,oops,like CN suggested.
     
  4. harshness

    harshness SatelliteGuys Master

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    A splitter may work but an OTA diplexer (joiner) is better as it insures that you don't get two signals for any station. You need to make sure that the joiner passes power so that the Mohu amp will continue to work.

    How many ways are you splitting the combined signal?

    The best way to figure out what's going on in a system is to limit the variables. Start by connecting just the Yagi antenna to the downlead and see if you get the VHF stations. If it isn't enough when directly connected, replace the Yagi with a bigger one. When it comes to VHF, there's no real substitute for size.

    Each connector that you go through reduces the signal (including the connectors that are on the power supply for the Mohu) so you need to plan carefully if you're going to be using splitters.
     
  5. harshness

    harshness SatelliteGuys Master

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    Now that I've looked at your TVFool report, I have t say that you've got a serious uphill battle there. The two-edge stuff is usually dicey at best but that they've got stations coming from opposite directions hurts. The Mohu may be omni/bi-directional but a Yagi isn't.
     
  6. Trip

    Trip RabbitEars Webmaster Staff Member HERE TO HELP YOU!

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    I don't understand what you mean here. The complaint, as I understand it, is about the three high-VHF stations on the same tower, KNOE (CBS/ABC/CW), KLTM (PBS Louisiana), and KMLU (Me-TV). Those stations are all LOS, not 2Edge.

    My question is whether or not KETZ (PBS Arkansas) comes in. That one's also VHF, but from the other direction; same tower as KTVE (NBC). I'm assuming that KARD (FOX), KMCT (IND), KTVE (NBC), and maybe a few other odds and ends, do work, all of which are on UHF.

    - Trip
     
  7. harshness

    harshness SatelliteGuys Master

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    I'm not complaining about anything. I'm pointing out that stations coming from different directions can be problematic if you're using a Yagi-Uda antenna (especially the ones rated for 60+ miles). My comments were not specific to the TS's situation.

    Citing what the situation is today may not represent the future. With TVFool in particular (however up-to-date it is) I'm not convinced that it contemplates a completely repacked landscape in some of these tweener service areas.

    We've been assured Next Gen TV will use the current DTV frequencies after they've figured out where to lighthouse several stations worth of DTV but I'm dubious that the proponents have a realistic plan with respect to adoption of ATSC 3.0. I get the feeling that they expect to meet their (and/or the FCC's) uptake goals within months but I expect that it will take much longer. If they shutter HD DTV channels in an effort to force it to happen, I reason they'll alienate their OTA viewers who will seek other avenues -- avenues like conventional pay TV and OTT providers where the stations won't be able to readily avail themselves of all the Next Gen TV revenue-generating goodies that they're salivating over.
     
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  8. Trip

    Trip RabbitEars Webmaster Staff Member HERE TO HELP YOU!

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    If your post is not specific to the OP, then why make it in the OP's thread? The OP is requesting help with his/her specific situation. (S)he actually seems to know a decent amount about the situation and has asked for specific advice. There was no discussion of ATSC 3.0, no mention of the repack (which, if you had bothered to do any research, you would know is already pretty much finished in this market), and no mention of interest in the 2Edge stations.

    - Trip
     
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  9. harshness

    harshness SatelliteGuys Master

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    If there's going to be a significant investment in a new antenna, what that antenna will need to be able to do in the next few years should surely be a consideration. If things go according to plan, that will include the completion of the repack and the introduction of ATSC 3.0 (Next Gen TV).
     
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  10. BDClark

    BDClark Topic Starter Member

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    Thanks for all the suggestions, folks! Stopped by Lowe's on the way home from work yesterday and picked up a mast as well as the RCA preamp that was mentioned earlier. I've got the preamp set to split the signals, with the Mohu coming in through the UHF side and the GE Yagi going through VHF. It took some aiming on the VHF side, but I'm pulling in 31 channels now as opposed to 20 before, including the KETZ that Trip was mentioning. It's a little weak, but I haven't seen any degradation on screen. Now my dad is absolutely thrilled to have Grit to watch his westerns, and for me I'm happy to get Heroes & Icons. Thanks again!
     
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  11. andy_horton

    andy_horton SatelliteGuys Pro

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    One thing I either missed or wasn't discussed is when using more than 1 antenna, shouldn't there be some kind of a few feet distance between the two? As I've played with my setup, before finally finding a happy medium with one antenna, placing 2 antennas 1ft apart caused interference vs when I adjusted to about 5ft apart on the mast. At that time the channels returned and one's from other directions I was aiming for also came in properly. Glad the OP got issue resolved
     
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  12. Wireless Engineer

    Wireless Engineer SatelliteGuys Family

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    Good point.
    Yes the distance between antennas (vertical distance) on the same mast
    needs to be at least a half wavelength at the lowest frequency or 3 feet in this case where a vhf high antenna is being used.
     
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