Black Magic Antennas


With the analog to digital conversion coming in one month, many people who generally get most of their TV from Over The Air sources tend to question if their current antenna setup will be able to receive the new digital broadcasts.  Today we will be demystifying the Black Magic that is antennas and how they work.



Getting Free TV

There are many ways to get TV.  You can get it via cable, satellite, even IPTV these days.  However, one option that is often overlooked by many is free Over-The-Air, or OTA, TV.  When cable and satellite services first became available, many people changed over to those services because the reception was often clearer and more channels were available to choose from.  While the number of channels available via broadcast antennas hasn’t changed much in most areas, the change from analog to digital will dramatically improve picture quality in most cases.  With digital TV you do not have the graininess that plagued analog tv – you either get the channel or you don’t.  If the signal strength is above a certain threshold, you will see a picture.  If it’s below that threshold, you will not.  If it’s right at that threshold, then you may get a picture that stutters or has pixelation.

So here’s the big concern.  If you’ve been watching broadcast TV, you’ve probably asked yourself if that old outdoor antenna on your house or little rabbit-ears on your TV will be able to pick up digital signals.  You’ve done some looking around and all of the retail stores are displaying "HDTV" antennas. Well, I’m here to tell you that there is no such thing as a "HDTV" antenna.  This is just a Marketing ploy designed to convince the consumer that the antenna hardware that they are currently using will not support the new standards and that the consumer needs to spend more money on new equipment.

Antennas are designed for one purpose and one purpose only.  They tune into certain frequency bands and and receive information from the broadcast stations.  The antenna doesn’t care if the signal that it is receiving is analog or digital.  That is a problem for the tuner.  The antenna just pulls in the information as best as possible.  The difference in antenna designs is that different antennas are better suited for tuning different frequency ranges.

In the case of TV, the frequency bands used are VHF and UHF.  Generally, HDTV antennas are designed for UHF reception.  This is not to say that they cannot pick up VHF signals, only that UHF stations will be amplified more, and thus have stronger reception.  An "HDTV" antenna will not necessarily pick up UHF TV stations any better than the antenna that you’ve been using for years and years.  The key is to determine if the stations you need to pick up are in the range that can be received by your antenna. and are both good sites for determining what signals are available in your area.


Distance/Line of Sight

Probably the biggest factor in determining whether or not you will be able to receive a station with a given antenna is how far away you are from the broadcasting tower.  As you move farther and farther away, the signal that is sent gets weaker and weaker, making it more difficult to pick up.

This is also affected by line of sight, meaning that if you have tall buildings, trees or anything else that blocks your ability to see the broadcast towers, you will suffer from a weaker signal.  Because of this, in order to get the best possible reception it is always recommended that you place your antenna outside (so that your house/apartment is not blocking the signal) and is as high as possible.



Another issue that sometimes arises is interference. In certain circumstances, the frequency that you are trying to receive for a TV show is also being used for something else.  In other cases, interference may stem from being close to power lines or the microwave when running.  There may even be cases where the signal is absorbed into surrounding materials, such as brick or cement, and not directed into the antenna.



Multipath is what happens when the signal is received from two places, slightly out of sync.  For example, one path could be directly from a broadcast tower, and the second could be reflected off of a large building behind you.  In the case of analog channels, this would result in ghosting on the screen.  Some tuners are better than others at determining which signal should actually be processed and displayed, but others are not so good, causing odd visual errors.  Multipath distortions can be reduced by using an antenna that is unidirectional, meaning that it primarily receives signals from only one direction.  If a signal is not coming from this direction, then it is not picked up by the antenna.  This works great if all of your TV signals are coming from the same direction, but if signals are being broadcast from all around you then this is not ideal because the antenna would need to be rotated based on which channel you are trying to pick up.



Hopefully after reading this you feel a little bit more comfortable about the upcoming analog to digital conversion that will be taking place in the US on Feb 17th (or June 12th ??), 2009.  We here at try to keep our readers well informed and up to date on what’s going on.  If you feel that something has not been covered fully or could use further explanation, please leave a comment in our forums and we will do our best to straighten things out for you.

And above all, enjoy your new digital broadcasts.