Don't fall for this digital TV antenna myth

Mikesleigh/Getty Images You'll need a digital antenna if you want to watch free local TV channels at home. Buying one is a bit of a minefield, however. One might claim to give you 150 miles of range, another 600, another 5,000, all from a plastic base inside your home. If those claims instantly make you skeptical, your instincts are right. The reality is that TV signals have physical limits, and while the marketers might try, no antenna can overcome the curvature of the Earth. Before you buy an antenna with the biggest mileage rating, it's worth taking a look at what really determines how far you'll be able to get a usable signal. Digital TV antennas can't reach 6,000 miles, or even 150 miles Hsyn20/Shutterstock If you head to Amazon and search for digital TV antennas, you'll see results that include indoor antennas with ranges that stretch from hundreds to thousands of miles. The worst offender is one claiming to offer 6,000 miles of range. To put that into context, the distance between London and Los Angeles is roughly 5,454 miles. No antenna in the world is letting you pick up the BBC in LA. It isn't giving you 1,000, or 500 or even 150. It's not a matter of power, either, as TV transmitters can broadcast a strong enough signal. Instead, to watch over-the-air local TV, what you'll need is a reasonably clear line of sight with the transmitter. When signals are transmitted from a transmitter, they aren't following the curvature of the earth. Instead, they travel outwards. The Earth is curved, so distant transmitters will eventually disappear below the horizon. Once a transmitter is beyond the horizon, its signal can no longer provide reliable direct reception. The horizon blocks the path. Atmospheric conditions might bounce it a little further, but not by far. You've also got buildings, trees, hills, mountains and more that can degrade the perfect line of sight, reducing the signal distance further. A digital antenna is just picking up VHF and UHF radio-frequency signals used to transmit encoded digital TV. Digital broadcasting can't eliminate these physical limitations, and there's no transmitter practically high enough to make 6,000 miles, or even 150 miles of range possible, even with an outdoor antenna in the perfect environment. High-gain antennas are also another marketing claim you'll need to watch out for. Antenna gain describes how well an antenna can focus on a signal in one direction, which is particularly important for outdoor antennas, but it doesn't guarantee better range. How far can a digital antenna reach? Michael Vi/Getty Images There's not a definitive answer to determine how far a digital antenna can pick up a signal from a TV transmitter. The environment, the terrain, the transmitter height and signal power all play a part in limiting a TV signal from the transmitter before we even begin to think about the antenna, because your environment (and any physical obstacles) will determine the range. Let's assume you're using an indoor antenna. One For All, a brand selling TV antennas globally, claims that its indoor antennas have a 25 to 60 mile range, but its "usual rule of thumb" is to only use one when you're 15 miles away from your nearest transmitter. It also recommends that houses surrounded by obstacles, like trees or buildings, situated more than three miles away from the transmitter will need to use an amplified TV antenna to boost the signal a little further. Outdoor antennas will let you pick up signals from further away. Placing the antenna outside means you're reducing the last obstacle, your house walls, and installing it at a high level improves line of sight between it and the transmitter. Antennas Direct suggests that 70 miles is the effective limit for line-of-sight for UHF signals, with low UHF and high VHF signals able to pass a little further, for instance. This makes these common marketing claims suggesting 150 miles range, or 6,000 miles, hugely unrealistic for over-the-air TV reception. The FCC maintains reception maps for over-the-air digital TV signals, but these are based on using an outdoor antenna at least 30 feet above ground level. As the FCC itself notes, indoor reception "may vary significantly." What to look for when buying a digital TV antenna Gado/Getty Images Unrealistic marketing claims aside, digital TV antennas can and do work, but before buying one, you'll need to work out your surroundings and determine the best type of antenna to buy. Your environment has a big impact on how well any antenna will work. Start by checking the distance to your nearest transmitter. The FCC's reception maps are a good option here, but you can also check with local TV stations to see what they recommend. Use this as your base point. If you're close to a transmitter, an indoor antenna could work, but the further afield you are, with more obstacles like big buildings and mountains, then an outdoor antenna is likely to be the best option. As we've already mentioned, amplified antennas exist. These work by boosting the strength of the signal received by the antenna before it reaches your TV. They help to compensate for signal loss, but they're not miracle workers. You can't amplify a signal if the transmitter power is too low or the distance too great, so keep that in mind.  Where you plan on installing the antenna matters, too. Indoor models are best placed near a window, or as high as you can put it for a clearer path to the transmitter. Indoor antennas are usually omnidirectional these days, but if it isn't, make sure to point it in the right direction. Thick, heavy walls can weaken the signal strength, as can any large appliances in its path. Outdoor antennas will overcome some of this, but you'll want to mount it as high as you can, pointing it in a general direction towards the transmitter. You'll also want to make sure that the cable quality between the antenna and TV is as good as it gets: no breaks, short cable runs and as few joins as possible. Most importantly, though, is maintaining a healthy dose of skepticism for any marketing. Ignore any mileage claims you see, because you're not getting hundreds or thousands of miles of range out of a TV antenna. If you're unsure, make sure to buy an antenna that you can try and return, just in case it doesn't work quite as well as you'd hoped.