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I find it a annoying and a pain to climb up to the roof and adjust the TV antenna so that I can watch my favorite TV program without distortion. I am not using satellite service which requires a dish to capture the signal and I know the antenna is designed to receive radiowave signals from the nearest broadcast tower and my TV will be tuned to a specific frequency. My question why does the orientation of the TV antenna in-situ affect the picture quality?

stock photo of a UHF antenna

Image is taken from Wirelesshack, please note that mine doesn't look exactly like this but close.

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    $\begingroup$ "I find it a annoying and a pain to climb up to the roof and adjust the TV antenna" - You might want to look into installing a rotor. Searching for "TV antenna rotor" should bring up a few results. Mount your antenna in the rotor and use the accompanying remote to rotate your antenna from the comfort of your couch. $\endgroup$ – 8bittree Oct 24 '17 at 15:20
  • $\begingroup$ Are you tuning in a VHF (channels 2 - 13) or UHF (14+) channel? Most of the antenna shown is designed to pick up VHF signals. $\endgroup$ – Hannover Fist Oct 24 '17 at 20:25
  • $\begingroup$ While this does not answer your question, if you have an unfinished attic there are some really good multi-directional ones that are designed for that location (no wind, snow, etc so they can be more complex/delicate, and are high enough up they get a good line of sight considering radio waves penetrate wood/roof shingles). $\endgroup$ – user57109 Oct 25 '17 at 0:21
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    $\begingroup$ Where do you live that there's still analog TV subject to distortion rather than complete/near-complete loss of signal decoding? $\endgroup$ – R.. GitHub STOP HELPING ICE Oct 25 '17 at 3:07
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Picture the radio waves from the TV transmitter as flat horizontal sine waves. You want the antenna to pick up the full width of this wave in the horizontal bars. So you need to point the antenna as directly as possible towards the TV transmitter.

dipole animation from wikipedia

Cell phones send the signal in a vertical wave (apologies for the oversimplification). This doesn't allow you to pick up a clear signal from as far away, but does mean that you can simply hold the antenna vertically and be able to receive a signal from any direction. Cell phones also contain a lot of modern signal processing electronics to handle a weak signal, which weren't available when TV was designed

P.S. You presumably only need to adjust it if you want to get a signal from a different transmitter. Or perhaps if the signal is really weak and the atmosphere slightly changes the direction the strongest signal is coming from.

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  • $\begingroup$ just for my curiosity wouldn't it be better if I were to bend those horizontal bar to form a circle? $\endgroup$ – user6760 Oct 24 '17 at 2:55
  • $\begingroup$ @user6760 - no because then the signal on one side would cancel out the signal on the other - you need the field to be different from one tip to the other - see the animation at wiki $\endgroup$ – Martin Beckett Oct 24 '17 at 3:00
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    $\begingroup$ what OP describes is in fact called a loop antenna and they do work quite well, as does a loop which has been squashed flat (which is called a folded dipole). in fact, a close look at the antenna pictured above reveals that one of the elements in the array is in fact a folded dipole. $\endgroup$ – niels nielsen Oct 24 '17 at 4:59
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    $\begingroup$ Something else the answer doesn't really menthion: a yagi is very directional (moreso than the dipole in this animation), and RF at those frequencies (especially in urban areas) can have all sorts of strange reflections, some of which (for various reasons) might end up being a better choice than the actual straight line path of the signal. For this reason, correctly positioning a yagi can often seem more like black magic than science. For instance, my indoor antenna works best if I point it towards the inside of the house away from the transmitter - the signal seems to be reflecting off a wall $\endgroup$ – Muzer Oct 24 '17 at 9:56
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    $\begingroup$ @Fattie - modern cell phones contain multiple complex antennae, so it's not quite that simple. $\endgroup$ – Martin Beckett Oct 24 '17 at 17:52
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The main problem comes from the fact that TV signals are highly directional. This means that if your antenna is "slightly off," the strength of the signal being received will drop significantly, causing loss of quality of the signal, and even the signal itself.

With the right combination of mechanical and/or electronic devices, the "pointing" of the antenna can be automated so that it always obtains the best available signal.

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  • $\begingroup$ specifically the antennae are highly directional and so need to point pretty accurately at the transmitter mast $\endgroup$ – Martin Beckett Oct 25 '17 at 1:57
  • $\begingroup$ @MartinBeckett or (sometimes, especially in urban areas) point pretty accurately at some reflection of the signal from the transmitter mast (see my comment to your answer). Which is obviously even harder! $\endgroup$ – Muzer Oct 25 '17 at 9:00
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    $\begingroup$ I was just making the point that it is the receiver that is highly directional - in case people were wondering how the transmitter highly directed the signal to every home individually $\endgroup$ – Martin Beckett Oct 25 '17 at 15:49

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