VHF/UHF Proximity to TV Antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by M6WCL, Feb 28, 2019.

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  1. M6WCL

    M6WCL Ham Member QRZ Page

    Hi

    I am in the UK and putting up a mast with a horizontally polarised yagi and a big wheel antenna for both VHF and UHF.

    My concern is my neighbour had a TV antenna, also horizontally polarised which is going to be about 2-3 m away from my mast.

    Their TV yagi is pointing in a direction that the worst case would be me transmitting directly to the side of it, and I am able to achieve 1 - 2m of vertical spacing.

    Are my concerns valid and is there anything I can do about it other than completely relocating the mast?

    Advice would be gratefully received.
     
  2. AA5CT

    AA5CT Ham Member QRZ Page

    Is this in the planning stage? Maybe you can test at low power and see if it has an effect ...
     
  3. G0JUR

    G0JUR Ham Member QRZ Page

    I would try and get as far away from their antenna as you can, you could be inviting a lot of grief.
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Isn't terrestrial broadcast-TV all digital UHF there today?

    If so, I doubt 2m could interfere with it even if you tried hard to do so.

    Re UHF, maybe...but I kind of doubt it unless their received BC-TV signal is marginal and almost dropping out to begin with.

    My OTA (broadcast) TV antenna is on a mast above my chimney and I can run 600W output on 432 MHz (key down carrier) and can't seem to interfere with TV reception at all, even if I aim right at my TV antenna; however the TV signal is very strong as we're line of sight and 28 miles from the transmitters. If the signal was marginal, interference probably would result.
     
  5. AA5CT

    AA5CT Ham Member QRZ Page

    @WB2WIK

    Exc, possibly harmonics from 2m operations appearing at 3x into the UHF spectrum. Only affect a CH or two though, maybe not at all given CH allocations.

    Also note that overload from OOB (Out of Band) signals to TV (from 70cm) could be an issue; both ants same polarization, 10 to 15 ft away ... could always rig up a LP (Low Pass) filter for use on neighbor's TV to solve that.
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd think if the TV OTA signal is strong (like LOS) it would be very difficult to interfere with it, as is my case here.

    With a weaker signal, no way to know without trying it.

    I do receive several non-LOS TV signals here, from out in San Berardino area (60-90 miles distant, well over the horizon); they're from mountaintop sites up very high so may not be "much" over the "radio" horizon, but they're too far for LOS. And even on those, if I run a kilowatt on 2m and retract my tower so the 2m beam is only a few feet higher than the TV antenna, and aim right at the TV antenna, I still can't interfere even with those quite distant stations. That kinda surprised me, but I've tried it a few times and no degradation to the TV at all.

    That supports the contention that TV "front ends" must be pretty robust nowadays and don't desensitize much from out of band signals.
     
  7. G0JUR

    G0JUR Ham Member QRZ Page

    Good for you Steve, however here it is still possible to interfere with ota tv, our digital transmitters are lower power than the old analogue tx,s were, also its possible for the rf to find its way into the TV
    via the coax and get into the audio stages of the tv receiver, Pin 1 problem, so best to think inverse square and get the vhf/uhf antenna as far away as he can. as usual ymmv. ;)

    Oh and they sell crap over here :mad:
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That could sure make a difference.

    I just looked up a typical local OTA TV station here, KCBS-TV, which is CH 2.1 virtual and in reality is on UHF CH 43. It's an HD 1080i channel, and runs 540kW e.r.p. and the antenna is 972' above ground on Mt. Wilson (transmitter site 5700' above sea level). Is that enough to be strong?:) It's 28 miles from me and provides a great signal with a 6" piece of wire indoors for an antenna, but I use a small UHF log periodic beam above the rooftop and it's amazingly strong; then, so are all the other channels from Mt. Wilson (dozens of them).

    But re "crap," I'd guess our TVs are generally the same crap (or I'd think so, anyway) -- Toshiba, Samsung, Vizio, whatever; there doesn't seem to be a lot of difference and I think they're all imported.
     
  9. KG5UBQ

    KG5UBQ XML Subscriber QRZ Page

    I have TV antenna near my VHF/UHF antenna and I know that TV signal is completely disrupted when I transmit. How close is neighbors antenna, and what power are you transmitting?
     
  10. M6WCL

    M6WCL Ham Member QRZ Page

    Thanks for all the answers.

    I think I am going to have to consider moving it to the other side of the property. The advantage here is that there is no nearby TV antenna. The disadvantage is that it is a lot more exposed and therefore I would be more liable from neighbour complaints regarding the visual aspect. I live on a hill so the house behind kind of looks down on me. I possibly over worry about getting a complaint but I would hate to have to take down what I already have!
     

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