Information Station Specialists is the best known source of travelers information stations, highway advisory radio, advisory signs and services needed to reach motorists with public service information. Learn more about Information Station Specialists.
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Frequently Asked Questions about TechTalk
Licensed Travelers Information Stations
Frequently Asked Questions Travelers Information Stations Highway Advisory Radio       
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  1. How far away can an AM advisory radio signal be heard?
    Licensed systems: Though the standard signal can usually be detected 5-10 miles away over open country, the strongest signal area is normally present in a 3-5 miles radius. Most operators position their "tune-to" signs within a 3-mile distance.


    The RadioSAFE Wide Area Broadcast System can operate above and beyond the conventional FCC signal limitations. Review the specific RadioSAFE system to discover its potential range and FCC licensing considerations.

    License-free radio systems designed to operate outdoors such as the InfOspot system (Talking House/iAM Radio with the Range Extender) will commonly have a much shorter range, up to ½ mile. License free transmitters with indoor antennas will have ranges in the hundreds of feet, depending on their immediate environment.

    See the estimated signal range for the radio system that is under consideration.

    In general, signal distances will be less in areas with very hilly or mountainous terrain or very poor soil. Distances can also appear to be less in areas where interference is present from other radio stations on or near the operating frequency or where high voltage overhead power wires or AM-broadcast towers are immediately present. At night and in the hours immediately before sundown and after sunrise, intermittent AM “skywave” interference can become a factor and make a station’s signal appear to have less range.

    Another variable that affects listeners' ability to hear the signal at greater distances is the quality of the radio receiver. Especially for car radios, sensitivity varies widely. Additionally, certain car engines and onboard computers produce varying amounts of their own interference, which can negatively affect reception especially in areas where radio signals are not strong.

    In general, however, the in-car radio receiver is the best instrument for AM radio reception.
  1. Can I hear the signal in homes as well as cars?
    Most communities do not promote this, because home reception varies widely with many factors, including:

    - Distance from the home to the AM transmitting antenna (AM signal level);
    - Quality of the AM receiver in the home;
    - Presence of an AM receiver that will work on loss of power (battery operated);
    - Structure of the building and interference sources that it may contain.

    With a maximum of 10 watts of AM power, your transmitter is optimized for in-vehicle listening. See our TechTalk article on signal penetration.
  1. May I put the AM antenna on our 100+ foot tower, building, silo (or other extremely tall structure)?
    We don’t recommend it, though it can be done when required. Your antenna is likely to work best on its own support structure over open ground. If you do want to consider an existing structure, the antenna-height restriction is 15 meters (49.2 feet) from tip to ground. So don't select a structure that is too tall. To function well, however, the antenna must be mounted at the top (not side) of the structure you do choose and must have the opportunity for a groundplane at the bottom.
  1. What may be broadcast on my AM Information Station?
    Generally speaking, this class of service is voice only, noncommercial in nature. You are not allowed to transmit music, mention commercial names (except in a noncommercial way, e.g., you may use air carrier names to provide directions at airport facilities) or provide any kind of commercial announcement.

    Although these radio stations operate in the AM broadcast band, they are licensed under public safety radio regulations; and decisions about content must be made with that in mind. The stations are not in any way meant to compete with full-power broadcast services. Broadcast content should be targeted to people in vehicles and should comply with FCC Rules Part 90.242.

    For more on this topic, please see our page on permitted broadcast content.
  1. Which frequency is the best to use at my AM Information Radio Station?
    There is no single right answer for everyone, partly because, in different areas of the country, all AM frequencies are not available due to FCC separation regulations. Generally, however, the conventional wisdom is as follows.

    The favorite is 1610. Here's why:
    • It is known by listeners as a common information radio frequency.
    • ts short antenna and small groundplane are somewhat more convenient to locate and install.
    • There are no commercial radio stations in the US on that frequency, which means that interference, especially at night, is usually less.
    • The short wavelength means less interference with power lines.
    The second favorite is 1620-1700:
    • Very few commercial radio stations are permitted on these frequencies, which lessens interference and produces good signal range for information radio stations using them.
    • Short antennas and small groundplanes are somewhat more convenient to locate and install.
    • The short wavelength means less interference with power lines.
    The third favorite is 530:
    • It is known by listeners as a common information radio frequency.
    • There are no commercial radio stations in the US on 530 to cause interference, the only source of night interference being Caribbean and Canadian stations in the eastern US after dark.
    • 530's long wavelength signal fades slowly and can produce a large fringe coverage area.
    The fourth favorite is 540-1600: Almost every car radio receives these frequencies, but there is often more nighttime noise and interference in this original AM frequency band.

    See our TechTalk article on skywave.
  1. How can I determine the right frequency for may information radio service?
    We offer a Frequency Planning Package (FPP) you may order to allow you to determine the right frequency. It includes a Frequency Search Service that produces a list of possible frequencies that the FCC will assign, a Signal Monitor Radio Receiver to allow you to monitor the frequencies and quantify the results, and the FCC License Application Service, which gets your application prepared and filed. The cost of the Frequency Planning Package is 100% subtractable from the price of the information radio station you order.
  1. May I use low power FM instead?
    LPFM has been fraught with misunderstanding about its complexity and cost. Public safety agencies, in particular, are wary of LPFM, because...

    1. The FCC rarely opens LPFM license-application filing windows and then just for brief periods.
    2. FCC separation rules for LPFM make obtaining frequencies near populated areas extremely difficult.
    3. The FCC allows more types of entities to apply for LPFM licenses, such as non-profits, fostering more competition for licenses making them harder to get.
    4. If applicants from this larger pool are granted license to popular frequencies, they are required by the FCC to share operation with other equally qualified applicants in the area.
    5. Running LPFM stations can be costly:

  1. Can any field tests be done to see how well an AM Information Radio Station would perform at a given location?
    Yes, but these tests are commonly done only where the exact coverage pattern or range needs to be determined. They are not often required, because transmitter power can be set anywhere in the 0-10 watt range to produce a standardized signal level at the FCC-mandated 1.5 km distance from the antenna. This means that unless there is severe terrain, very poor soil or there is an interference potential, almost all TIS stations will produce the same coverage pattern. As a result, pre-testing isn't often required. If it is desired, however, we offer a self-test service called EventCAST

  1. What if I don’t have room for my groundplane beneath my antenna?
    Assuming your antenna will be mounted on the ground, Information Station Specialists can offer a number of "vertical groundplane" solutions that require no more physical space than the pole itself requires. There is some additional cost. Inquire at the time that you are planning your installation. See our Vertical Profile Antenna Support and Grounding System.
  1. Can this system be used for the AMBER Alert Program?
    AMBER Alerts were not anticipated by the FCC when the service was introduced, but AMBER Alerts are a perfect addition to content that is now allowed, under the heading "imminent danger." See our Permitted Content webpage, which gives you a formula for analyzing content.
  1. Why might I not want to place my AM antenna on the roof of my building?
    We do not recommend installing antennas on rooftops or otherwise within 50 feet of buildings or other locations that contain telecom/AV systems because of the potential for interference.
  1. What does an information radio station call sign mean and may I choose it? Why are there seven characters, three of them numbers? How often must I broadcast my call sign?
    Federal Communication Commission Rules (part 90) govern the licensing of information radio stations (TIS) issued to local government entities such as states, cities and counties. The Commission assigns 7-character call signs to all - 4 alpha letters, followed by 3 numbers.

    Modern TIS call signs that are issued by the FCC begin with a “W” (though many years ago some were issued that started with a “K”). The next 3 letters and 3 numbers are sequential, based on when the Commission grants each license.

    Although the Commission does not permit applicants to request specific call signs, in a few instances (when licensees indicated certain call signs were objectionable), the FCC granted changes.

    The FCC requires that the full 7-character call sign be broadcast every 30 minutes (or more) in English. Sometimes station operators inadvertently drop off the three numbers of the call sign, probably because standard broadcast stations (licensed under FCC Part 73 Rules) don't have numbers in their call signs and have only three or four characters (WGN, WABC, etc.).

    Information Stations operated by federal government agencies are licensed through the NTIA (National Telecommunication Information Agency) rather than the FCC and do not necessarily follow the same format. In some instances, these call signs may begin with a "K," may have only three letters or may have no numbers.

    Information Stations authorized by branches of the military are not issued call signs.
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FAQs about License-Free Part 15 Stations
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Information Radio Station is a generic term synonymous with Travelers Information Station (TIS), Highway Advisory Radio (HAR) / Highway Information Systems & Low Power Radio Stations (LPR). Operation of the stations is governed by FCC Part 90.242 Rules. A FCC license is required. Information Radio Stations may be fixed or portable. Subcomponents may include transmitter, antenna and ground system, digital voice player, wattmeter, cabinet with conventional or Corbin locks, lightning arrestors for RF, power and telephone lines, coaxial cable. Most stations employ black maximized antennas to discourage ice accumulation and security measures to prevent unauthorized program access. Options include synchronization, battery backup, solar power, remote programming by local, network or telco, multi-station audio distribution via RF or LAN / WAN or wireless network.