I have a TV. I’m too cheap to buy cable and too lazy to install an outdoor antenna on the roof. I’ve already moved my rabbit-ears style TV antenna away from the TV set and any other devices that are likely to interfere with the signal.
Reception is still not good, but if I fiddle with the orientation of the antenna I can often improve reception for a given station. The optimal orientation - length of the antenna “arms”, angle of separation between the arms, North/South/East/West direction of the arms - seems to be different for each station.
In addition to being cheap and lazy, I also have lost much of my understanding of practical physics. So here’s the question: What’s the relationship between the orientation of an antenna (rabbit-ears, specifically) and the quality of the received signal (let’s assume, for the sake of argument, that there are no large buildings, mountains, or other signal-blocking things between my set and a broadcasting device). That is, if I know the frequency on which the station broadcasts and the location of the nearest tower broadcasting the signal, can I determine optimal orientation of the antenna for a given TV station?
I am pretty sure you want the two ears to be in a plane perpendicular to the direction to the station. With less confidence I also think you want them to be symmetrically long and equally vertical versus horizontal, and that you want the tips of the ears to be about as far from each other as half the wavelength. For channel 2 the wavelength is maybe 5’ or so and for channel 12 it’s maybe 2’. All the UHF numbers would work differently.
It’s a dipole antenna. It should be perpendicular to the line-of-sight between the transmitting and receiving antenna. Since the signal is horizontally polarized, the receiving antenna should be parallel to the horizon.
TV transmissions are typically circularly polarized, so orientation of the poles is largely immaterial. Pole length is the important factor here; orientation of the poles in relation to each other affects the impedance of the antenna system which can make a difference with weak signal reception.
Seems I may have confused satellite with land-based TV, from searching around. But, I could have sworn I read someplace that TV was circularly polarized. Either my memory is failing, or the article I recall reading was incorrect. Both are distinct possibilities.
I suppose it’s possible but I’m not sure why any station would do it unless required to. Generating a circularly polarized wave requires the transmitting of two signals phased at 90[sup]o[/sup] to each other. According to my books on TV frequencies the propagation is by space wave and horizontal and vertical polarizations are treated essentially the same so either one can be used.
As to the proper orientation of your rabbit ears. The most effective method is to try various orientations and use the one that works best. If none of them work well, you need a better antenna. It really is as simple as that.
If the TV stations you want to receive are all in the same general direction you want a directional antenna. That’s one that receives signals well from a preferred direction and not so well from other directions. Here’s a description of the yagi antenna which is the usual type used.
The difficulty here is that if the stations are scattered around in several directions you need some sort of rotator to point the antenna at the station you want to receive.
Better has a lot of different definitions depending upon the use of the antenna. In this case it usually means one with a large capture area so as to recover as much signal as possible. A large capture area equates to a directional antenna in this case.
Napier’s numbers for the wavelengths are off. For channel 2, the wavelength is about 5 meters, not 5 feet. For the lower VHF, channels 2 through 6, the optimal length runs from close to 9 feet to just under 6 feet. You’ll probably just want the arms extended as far as they go.
For channels 7 - 13, the wavelength is about 5 feet, and you’d want the total length to be about 2.5 feet. Odd multiples of a half wavelength also work, so you could make the total length about 7.5 feet, which is conveniently the same length as you want for the lower VHF channels.
Putting the antenna physically higher up will often get a stronger signal. Also, experiment with angling the ends towards the direction of the stations you want.
I’ve always found that moving the actual location of the antenna works better than trying to manipulate it. Perhaps this is because I’m orientating it into one of the 7.5’ planes mentioned above, or because (as you specifically excluded in the OP) there are things blocking the signal in one part of the house, but not in another. YMMV.
