If I had two (identical) Yagi antennas, and wanted to point them in different directions to get stations from opposite sides of my location, would there be any advantages to mounting them both (vertically) on the same mast, as opposed to side-by-side on the roof?

I'm not stacking them in order to get better gain; I just want to pick up additional channels from two separate directions.

  • 1
    Not a definitive answer, but in general (vague recall of antenna theory) I think maintaining separation between them is likely better than having them very close to each other - but that separation could be vertical or horizontal. So if you have stations on opposite sides, putting the antennas on opposite ends of the building would likely be better than any "side by side" configuration. Certainly one seens many stacked vertically, but that's both a "here's a tower, let's use it" and "usually an engineer specs how the various antennae are arranged on the tower" situation. – Ecnerwal May 12 '19 at 14:25

It depends on the polarization of the signal.

If you're unsure about the polarization of the signal, look at the antenna elements of a stationary yagi antenna to see if they're horizontal or vertical. Mobile antenna are often just a single vertical element, so it's not a foolproof way to tell. An internet search would also work.

TV is horizontally polarized.

For horizontally polarized signals, vertically on the same mast, spaced at least 1 wavelength apart would be ideal to prevent most signal attenuation.

For vertically polarized signals, use separate masts, spaced at least 1 wavelength apart would be ideal to prevent most signal attenuation.

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  • This sounds like a good answer, but in practical terms as a consumer how could I know the polarization of a given signal, which would lead me to the decision to stack vertically or horizontally? – orlando21 May 13 '19 at 6:01
  • @orlando21 OK good point. I updated my answer. – Dotes May 13 '19 at 17:30

A general rule of thumb is that you should maintain at least 1/4 wavelength separation between the antennas. More is better - within reason.

Not sure where you are located, but in some areas in the US, TV is only broadcast in the UHF spectrum (470 - 806 MHz), while other areas still have VHF-High and VHF-Low channels as well, though it seems those are being phased out (174 - 216 MHz and 54 - 88 MHz respectively). The minimum separation for each of those bands then would be:

  • UHF: 6.3 inch - 470 - 806 MHz - Channels 14-69
  • VHF High: about 5 ft 8 inch - 174 - 216 MHz - Channels 7 - 13
  • VHF Low: 18 ft 3 inch - 54 - 88 MHz - Channels 2 - 6

Note that the channels numbers are physical channels - with digital OTA TV, these are not going to match what your TV displays (it shows virtual channel numbers). You will need to check a channel listing website like rabbitears or TV Fool in the US to get the physical channels you are going to be able to receive.

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