OTA HDTV Reception Q&A

Updates on the DTV transition and how to receive over-the-air digital television for free.

Location: Richmond, IL, United States

Hello there! I created this blog to share the information about over-the-air HDTV reception you have been wearily searching the Web or calling technical lines for, whether you have decided for less expensive means to get your favorite TV shows, or still adjusting from the over the air broadcast DTV transition that occurred on June 12, 2009. After working for a leading antenna manufacturer for almost 5 years, during which time I've shared my expertise with those who asked on the phone and by email at work, I decided to do the same in the Blogosphere! Confused about getting your local HD channels? Just click through the archives, some of the most useful information is in the early posts from 2005-06. If you want to get in touch with me with antenna related questions, just leave a comment anywhere on this site.

Saturday, July 15, 2006


When I started this blog, I wrote on how to use http://www.antennaweb.org/ to select an antenna and aim it for off-air DTV and HDTV reception. This week I visited the site, and I discovered that the address information page has a new advanced feature, an "options" feature.at the bottom of the address page, which will be useful to truly determine your local DTV off-air reception capability. The options, which are expanded on the browser using a Flash plug-in, allows you to enter Latitude and Longitude coordinates as well as the height in feet of the antenna above the ground. The trick is that the coordinates need to entered in decimal degrees, and not degrees minutes and seconds. I will give you a trick to convert from DMS to decimal in a little bit.

Before this option was added by site creator Decisionmark (based in Iowa) in association with the Consumer Electronics Association (CEA), the most accurate results were presented if the user entered a complete address, although a zip code was the minimum requirement. Some users are still a bit hesitant, however, in providing address information over a Web site, and the site is not secure. But now with providing latitude and longitude information instead of the address, a user can get accurate information on local off-air coverage without sending address information over the Internet.

Playing around with coordinates for my office at Winegard Company in Burlington, Iowa, I noticed that when I entered latitude longitude coordinates I once recorded while helping the plant set up a production test for RV dishes using GPS technology to lock onto satellite TV "birds", and compared the results with entering the address of the office, I got an interest difference in the results. The latitude/longitude results added a DTV PBS station from Macomb, IL, about 30 miles southwest but broadcasting at a relatively low power, which I did not notice when entering the address. The PBS station services Western Illinois University based in Macomb. I mention the fact that the station transmits DTV at a relatively low power because its reception does become spotty here in Burlington as the field strength starts to get low. In such cases, the field strength starts to vary significantly between strong voltages and nulls, sort of a "checkerboard" effect, and the broadcast would come in simply by relocating the antenna by just a few feet.

One other important point to mention is using the latitude/longitude entry instead of the complete address is you still may need to select the state where you live. This will allow you to see the street level map if you select that option on the results page. When I checked the street level map, the selected location where the field strengths of the off-air channels were predicted was noticeably different than the location of the address, but only by what appears to be a couple hundred feet on the roof of a fairly large manufacturing facility taking up a city block. This would prove to me that changing the coordinates by just a little bit may determine if an available station signal would be in a "checkerboard effect" at the given location, and trying different locations for an antenna may lead to good reception of a hard-to-get digital channel with a small-to-moderately sized antenna.

The other key "options" field is the height of the antenna, entered in feet above ground, which can be measured with a ruler tape. This entry is above ground, and not sea level, the prediction is already factoring in the terrain of the neighborhood. Because terrestrial VHF/UHF television signals are transmitted with a direct path, and do not follow the natural curvature of the terrain like AM radio signals do, antennas that are mounted at rooftop heights outdoors in most cases will collect more signal. So, by measuring the height of where you may want to put up an antenna, either on the roof or on the wall, and by determining the latitude/longitude location of the antenna, you may be able to use antennaweb.org to locate the "sweet spot" of best reception for your location even before buying the antenna, cable, or mounting equipment.
So how do you determine the latitude/longitude? With GPS devices that are becoming more easily available. GPS devices use latitude/longitude information to determine where you are and to set up navigation directions. Some newer mobile phones have GPS location technology as a feature built right in, so take a look at your cell phone manual and see if you get can latitude/longitude information from it. You can also get GPS navigation devices from many different places, or borrow one from a friend or neighbor. Garmin is a leading manufacturer of GPS-based navigation handheld devices.

If the device gives latitude and longitude information in degrees, minutes, and seconds (DMS) only, and not in decimal degrees, here is how to convert DMS to DD using a calculator. First, take the MINUTES integral value and multiply by 60 to convert to seconds. Then, add the result to the SECONDS value read on the GPS device. Divide the result by 3600, and add the intergral DEGREES value read on the GPS device. Write the result down and be prepared to enter it into the options field at antennaweb.org. Play around with the GPS values while leaving the height field blank and indicating you are in a single-story home. Once you find the best results, use the GPS device to find the sweet spot and plan to mount your antenna there. You will want to minimize the violet results if you want to use a relatively small antenna from off-air reception outdoors, and play around with the height value as well.

Now understand that antennaweb.org assumes the antenna is outdoors with no visible sources of blockage (i.e. tall buildings, trees, or other radio sources) in the compass directions listed in the results. If you mount the antenna in an attic, the signal strengths are cut in half by standard composite shingles on plywood. However, here is a trick to see if indoor or attic reception is possible. First of all, try using the GPS device indoors by your TV set or in the attic and see if you can get a reading. If you can't, your building may be pretty much shielded from receiving off-air signals and putting an antenna outdoors may be the way to go. If you can get a reading, or are able to use a cell phone indoors, then indoor reception might happen.

If that is the case, use antennaweb.org and enter "0.1" in the height field; the program requires a positive non-zero value to get results, and 0.1 is practically right on the ground. Because of the direct nature of broadcast TV signals over-the-air, the signal strengths are expected to be fairly weak, and the results will be reflected on your available station list. So, if you use this trick and see the DTV stations you want listed and not listed as violet, then you just might be able to use a small, unobtrusive antenna indoors or in the attic space to get the off-air DTV channels you want. If you see these results and you are able to aim an antenna through a window in the listed compass direction, then an indoor antenna just might be all you need if you just want to use one off-air DTV tuner in your place. If you do not see the stations your want, or you do but most of them are in violet, then you will either need to use the largest possible antenna that can fit in your attic space, or put an antenna outside.

So I am excited that Decisionmark has added this new feature to what is already a very useful Web site. Now a customer can use GPS and measurement techniques that are easy to carry and affordable, and this useful free online tool to find the "sweet spot" where an antenna of manageable size may be all that is needed to get local broadcast HDTV for free over the air, or at least help a customer make an informed decision on whether or not an off-air antenna is worth the cost or the trouble. I feel that this is good to know as the attitude at work right now with the satellite companies beginning to provide local HDTV via the satellites and USDTV in bankruptcy is that indoor antennas may become the hot sellers. It is just a matter of marketing them right, and antennaweb.org just gave me some big help.


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