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Signal Search Map Instructions

Using the Search Map

The search map is a tool to help you determine the available local TV stations, their strengths, and how to aim an antenna to find them. To do so, you must first pick your location and some key parameters.

There are several different methods you can use to select your location.

  • You can search by address using the box at the bottom left corner of the map. Once it locates the address, click the "Move Pushpin to Center of Map View" button to place the pushpin at the retrieved address. Be sure to check the map and make sure that it has put you in the right spot. If not, you can then drag and drop the pushpin to the right location.
  • You can drag and drop the pushpin exactly where you want it. You can zoom in or out either by scrolling while your mouse is over the map, or by using the zoom controls at the top left corner of the map. If you lose the pushpin while zooming or adjusting your map view, you can retrieve it by clicking on the "Move Pushpin to Center of Map View" button.
  • You can retrieve your location using your browser's location services or your device's GPS if it has one. To do this, click the "Get Location" button and it should put your location on the map and put the coordinates in the Lat/Lon fields. Use the map to verify that the placement is correct, and you can drag and drop on the map to adjust it if necessary.
  • You can directly enter decimal coordinates into the Lat/Lon fields. When you do so, the map should update to show the location you've entered. Alternatively, you can enter the decimal coordinates together in the latitude field separated by a comma or a space. While this will not update the map, it should work when you search.

Once you've set your location, you may also adjust three additional settings.

Shift Shown Location for Privacy is a setting to determine whether to display your exact location in the report. If this is set to "Yes," then while your exact location will be used for the various calculations, the coordinates used to show the results of those calculations will be rounded to two decimal places, including in the map view. If this is set to "No," then the exact location will be both used and displayed in all cases.

Minimum Search Distance is the minimum distance within which stations will be included. Because it is easier to pick a group of stations out of a database with a square than with a circle, the minimum distance is the distance from the center of the square to the midpoint of any of its sides. That means that while a 60 mile minimum search distance will definitely contain every station within 60 miles, it will also contain stations towards the corners of the square that may be as much as 84 miles away.

Note that as you change the minimum search distance, the box shown on the map will also change in size as well. This is so that if you have a sense of where the TV stations you wish to evaluate should be coming from, you can eyeball it from the map view. Please also note that as you increase the minimum search distance, the study takes longer to run. Generally, most viewers will not benefit from a distance greater than 60 or 70 miles, but there are certainly cases where those longer distances could be useful.

Antenna Height Above Ground is the height of the receive antenna above ground level. This height must be 13 feet or greater for the study to run successfully.

Once you're done, click "Go" and you can move on to the next section.

Reading the Results Lists

The results list should be pretty straight-forward, but has some nuances that are worth pointing out. By default, it shows field strength values in dBuV/m, and the rows are sorted by that field strength. But all of this is adjustable, and the full interface should have a once-over.

Starting at the top, you will find that there is a direct link to the study, which can be used to share your study with others. These study results are stored on the server, and should be valid for at least 30 days after generating the study. Each time the study is viewed, the "last accessed" date is updated in the server, so a study that is in heavy use for some reason would not be deleted, while one that has been forgotten about will be deleted after some amount of time.

Beneath that and to the left are some useful pieces of information about the study, such as the coordinates evaluated (rounded, to protect privacy), when it was generated, the receive height used, and the minimum search distance. Beneath that, you have the option to change the sorting of the rows to signal power, RF channel, display channel, distance, or direction. Beneath the sort options, you can also change the field strength units to the signal power units of your preference. Beneath the unit selection, there is an option to hide stations that are believed to be off the air. Finally, at the bottom, you can switch the list of channels to reflect potential future facilities that have been applied for, or view maps for either the current facilities or the potential future facilities.

To the right of this information is the "bullseye" chart. If the receiver is in the center, stations are organized by the direction they're in, and then are closer if they're stronger and further away if they're weaker. The channel numbers given are RF channel numbers, not display channel numbers.

Below that header information is the list itself. If a row is red, the station is on low-VHF. If a row is yellow, the station is on high-VHF. Cyan and white rows are UHF stations. The information provided is as follows:

Channel - The display channel number is given first, followed by the RF channel number in parentheses. If you are trying to determine what range of channels your antenna needs to be able to receive, use the number in parentheses. Additionally, if this column is gray for a particular row, then the station is channel sharing on the signal of the station above it.

Callsign - Clicking on the station's callsign will take you to the RabbitEars main listing for the station.

Network - Basic network affiliation information. Much of this comes from the FCC database, which may not be complete or accurate. Detailed network affiliation information is found in the main listings, and that is hand-managed. A callsign following a // indicates that the station simulcasts another or, if the "Channel" column is gray, is a channel sharing station.

Community of License and State - This is the specific community of license for this station.

Map - Click the icon to see the station's coverage map, with a red marker where the study location is.

Transmitter Distance (Miles) - This is the distance to the station. If you click the link, it will take you to the terrain path profile for the station. More information on the terrain path profile can be found in the appropriate section below.

Direction (True) - This is the direction of the station relative to true north.

Direction (Magnetic) - This is the direction of the station relative to magnetic north. This is the value to use with a compass.

Field Strength or Signal Power - This reflects the signal strength of the station in question. It is given in the units selected in the drop-down at the top of the screen.

Next to the strength number is a statement of "Good", "Fair", "Poor", or "Bad", which is always based on the field strength rather than one of the signal power numbers. "Good" means that an indoor antenna should have good luck with the signal. "Fair" means that an indoor antenna may work, but an attic or outdoor antenna definitely would. "Poor" means you will likely need a good outdoor antenna, and "Bad" means there is likely little or nothing that can be done to bring that signal in.

Signal Margin - This field is somewhat less useful than it sounds. It's the difference between the calculated field strength and the FCC's minimum field strength for reception. It could be useful, but the Field Strength or Signal Power column is likely to be more useful to you.

Repack Info - If this column is blank, then the station is not-repacked, or is an LPTV or translator station whose repack status is not being tracked. Otherwise:

  • L means it has already repacked and should be on its final licensed facility.
  • R means the station has moved to its new channel, but is at reduced coverage for some reason.

Note that if the last three columns are pink, that means the station is believed to be off the air. Additionally, if the last three columns are green, then the station is broadcasting in ATSC 3.0 (Next Gen TV).

Reading the Results Maps

The results map is relatively simple; showing lines between the estimated receive location and each tower. This is designed to give you a sense of where the various stations come from and what kinds of terrain and obstructions you might have.

The color of the line and the icon match that of the strongest signal on that tower. Additionally, if you click on the icon, a list of stations using it will appear. Hovering over a given station will give you the predicted field strength or signal power, depending on the units selected at the top of the page.

Understanding the Terrain Profiles

The terrain path profiles show the terrain between the selected transmitter and the receive location, adjusted for the curvature of the Earth.

The green line represents the terrain, while the red dotted line shows what a line-of-sight path is or would be. The blue line shows the actual path out to three obstructions, and the number of obstructions is reflected in the text at the bottom center, which indicates "LOS" for no obstructions, "1-Edge" if there's only one obstruction, "2-Edge" if there are two obstructions, and "Tropo" if there are more than two obstructions.

Search Map FAQ

Q. What software powers the Search Map?
The Search Map is powered by the FCC's TVStudy software. This is unlike the Longley-Rice coverage maps, which are powered by the SPLAT software.

Q. Why do address searches sometimes fail?
RabbitEars used to use Google Maps for both map display and address searching, but Google changed their pricing to the point where it would have cost a significant amount of money to continue using it. This was a problem, considering RabbitEars has a budget of $0. As such, the code was moved to using Leaflet for maps, which can retrieve the multiple map layers now available, and to using OpenStreetMaps for address searches. The OpenStreetMaps works in many cases, but in others, it does not. In those cases, you might want to look up your address in Google Maps or on a webpage like this one and then copy and paste the coordinates into the RabbitEars Search Map.

Q. Why are Mexican stations missing from the results?
RabbitEars was originally built on top of a copy of the FCC's CDBS database. The FCC has since replaced CDBS with LMS. RabbitEars has long had code that translates the ISED Canada database into CDBS format, and code to convert it to LMS was only recently written and implemented. Similarly, a Mexican spreadsheet was converted into CDBS format, but such a conversion has yet to be made to LMS format. When that conversion happens, the data will automatically appear in the search results, but for now, it is absent.

Q. Why doesn't my reception match the prediction from the Search Map?
Because they are predictions, they can only calculate based on the information they have. For example, the propagation model does not take into account tree cover, which can be a substantial cause of reduced signal in some instances. Further, sometimes atmospheric conditions can enhance or hinder the reception of signals, leading to over- or under-stating reception at a given time. Finally, the Search Map does not calculate interference from any source, and strictly calculates the strength of each signal. Therefore interference, either from other TV stations or from other sources, is not included in the calculation.

Q. Is there any further documentation?
A user named Dave Poole put together a primer for using and understanding the Signal Search Map. It is provided as a PDF and is available for download here.

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