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There is no such thing as an HDTV antenna!

Over-the-air (OTA) HDTV is becoming more and more popular. For someone used to the noisy pictures of analog TV, it’s hard to believe how amazing the quality of HDTV broadcasts can be. In fact, free-to-air HDTV channels are often better quality than the same channels received through a paid HDTV satellite subscription. All you need to enjoy OTA HDTV is an HDTV with a built-in HDTV tuner and HDTV antenna.

Hey? What kind of antenna? If you have a PhD in Electrical Engineering and have never heard of the type of antenna called an “HDTV antenna”, it’s not because you were a bad student. HDTV antenna has nothing to do with physics and engineering. It was invented in marketing departments. Marketing found an effective trick to boost sales of TV antennas. HDTV is a hot thing these days. Call essentially the same device an HDTV antenna, and it sells better. It makes people believe that they have to buy an HDTV model or an HDTV-optimized antenna to watch HDTV broadcasts. This is very far from the truth.

The hype of HDTV antennas created a huge misconception regarding TV antennas used for HDTV reception. This article is an attempt to clarify this issue.

Do you know what a normal antenna is? The antenna is a piece of metal designed to resonate at a specific frequency and respond over a certain range of frequencies. TV antennas are designed to operate in the ultra-high frequency (UHF) range, very high frequency (VHF) range, or both. Any station broadcasting in the VHF/UHF frequency bands can be picked up by a VHF/UHF antenna and transferred to the TV.

All television transmissions, digital and analog, are on the VHF and UHF bands. Over 90% of HDTV transmissions are on UHF and less than 10% on the VHF band. What is important from an antenna perspective is that HDTV falls within the bandwidth of a normal VHF/UHF antenna. It’s not an HDTV antenna, it’s not an HDTV optimized antenna, it’s just a normal TV antenna. What makes a signal HD is its content, the way a signal is modulated, and not the carrier frequency on which it is transmitted. By contrast, the antenna does not know anything about the modulation and content of the signal. So you don’t need an HDTV antenna to pick up the HD signal. An antenna has no idea what the resolution of the signal is. It can be HDTV, SDTV, NTSC, whatever. The job of an HDTV tuner and HD television is to demodulate the signal and present the actual content on the screen.

Well, antenna bandwidth and frequency response are not the only parameters that are important for clear TV reception. An antenna has other important electrical and spatial properties, such as antenna gain (directivity) and a high front-to-back (F/B) ratio. It could be assumed that an HDTV antenna should be more powerful in terms of F/B and gain parameters. Does HDTV reception place more stringent requirements on antenna gain and F/B ratio?

There is a common, but erroneous, belief that more antenna gain is needed to receive digital TV. I don’t know where the hell this belief comes from, because the situation is exactly the opposite. HDTV has much better immunity to noise and interference than analog television and can produce high-quality video with a significantly lower signal-to-noise ratio.

Another important specification, the F/B ratio, has to do with the antenna’s ability to handle multipath signal propagation from the towers to the receiving antenna. The higher the F/B ratio, the better the multipath rejection (also known as ghost suppression). Without going into technical details, we must say that the HDTV signal is a bit more sensitive to multipathing because it has a slightly higher bandwidth. Multipathing causes dips in the signal spectrum, while we want to keep the spectrum as flat as possible. When the signal content is spread over a larger portion of the spectrum, it is more likely to be distorted by multipath. Basically, what TV equipment manufacturers try to do in so-called HDTV optimization is to keep the spectrum flat across the entire frequency band. It is important that the HDTV antenna has a high F/B ratio in some areas where ghosting can be a problem. The point, though, is that most cheap, old-fashioned, directional TV antennas have a good enough F/B ratio to handle multi-path propagation of the HDTV signal and keep spectrum distortion to a minimum. If an antenna can handle an analog signal, it can also handle a digital signal.

There is nothing specific about a TV antenna being used to receive HDTV. When choosing an HDTV antenna, check the really important parameters, such as directivity, gain, F/B ratio. These specifications are important for the reception of digital and analog transmissions. HDTV optimization is probably the least important factor to consider.