1.0 LPB

LPB, Inc. was founded in 1960 specifically for the development and manufacture of carrier current AM transmitters. Since then, LPB has placed more than 30,000 transmitter products into operation worldwide. LPB continues research into methods of improving the technology of carrier current and is the acknowledged expert in the field. LPB has served as design consultants and engineering consultants for government and private projects in many different countries. Dozens of manufacturers regularly use LPB transmitters to demonstrate their products.

LPB transmitters are Type-Accepted by the Federal Communications Commission (FCC) for commercial operation from 520kHz-1700kHz. These units are available on other frequencies for use outside of the United States. LPB has modified transmitters in operation worldwide from 261kHz to 1700kHz. Applications for LPB transmitters include standard commercial broadcast operation, specialized systems for the hearing-impaired, tunnel rebroadcasting systems, stadium broadcast systems, and roadway information systems. LPB engineers are always willing to explore new applications and design systems for them.

This brochure has been designed to introduce LPB and detail some of the more common applications for LPB transmission equipment. Specialized systems are briefly mentioned in order to emphasize the flexibility of LPB in a low power/limited area broadcast environment. Please contact LPB directly for information on specialized designs for your applications.

2.0 Limited Area Broadcasting (back to index)

The objective of limited area broadcasting is different from conventional commercial broadcast applications. Instead of trying to cover the maximum area possible, limited areas are chosen and a broadcast signal is focused on them. In the United States the FCC has defined limited area broadcast methods and limits under Part 15 of its Rules, which do not require either a license or notification for operation.

Many countries don't have any rules for limited coverage systems as they are unique and often specialized. FCC Part 15 may serve as a guide to government communication ministries in some of these nations. In essence the FCC permits controlled limited area broadcast systems to cover individual structures, or defined areas provided that there is no resulting interference to a licensed broadcast facility. These areas of coverage are defined by the type of broadcast method being used.

2.1 Carrier Current (back to index)

Carrier Current broadcast systems utilize an impedence-matching Transmitter Coupling Unit to impress a Radio Frequency (RF) signal on the AC wiring of a building. This method essentially turns the AC power wiring of a building into an antenna which covers the interior of the building and some of the surrounding area. A typical system would consist of a transmitter and coupling unit in each building which required coverage (although electrical tricks can sometimes reduce the amount of equipment needed) and a Distribution Amplifier to send audio to the transmitters via telephone lines. LPB has been manufacturing, designing and installing Carrier Current transmission systems since 1960.

Applications

Carrier current systems are employed in a variety of locations, most frequently in educational settings. More than 1,000 colleges and high schools in the United States and other countries have installed LPB carrier current systems. The relative ease of installation, maintenance and use of carrier current equipment has made it very appealing for schools. A constantly changing student body and lack of professional engineering skills do not limit the operation of carrier current equipment!

The Radio Reading Services for the Blind distribute signal to individual and group housing around the United States using an FM subcarrier and a subcarrier receiver to supply audio to LPB transmitters. These transmitters permit the blind to listen to book readings and other services with a common AM receiver. There are more than 100 of these systems in operation in the US.

Carrier current systems also operate in government administrative buildings (in 2 US states) in order to rebroadcast speeches from the Senate meeting rooms. Local social groups have developed carrier current systems for urban neighborhoods and churches in a variety of major cities. Many auto racing tracks have carrier current systems broadcasting race information to fans (information which might otherwise be drowned by engine noise). The possibilities are fairly unlimited for small carrier current systems.

Carrier current systems traditionally receive audio via a twisted pair telephone line. LPB has recently developed a fiber optic option for its carrier current interlinking. Using fiber optic lines LPB has been able to remove some of the transmitter requirements from these systems and replace them with linear amplifiers. These systems are able to achieve a greater audio bandwidth thanks to the use of fiber optics, and eliminate any potential for beat note interference. Contact LPB for more information on fiber optic linking.

2.2 AM or FM Stereo Radiating Coaxial Cable (back to index)

LPB has developed a proprietary radiating coaxial cable which is lighter and more flexible than others available. A specially woven outer braid creates a leakage pattern which follows the entire length of a cable. Cable systems can have either AM or FM Stereo inputs, or both through the use of filters.

The LPB "NF" series of radiating coaxial cable is available in two models : NF-1D (0.29") and NF-2D (0.42") with a variety of polyvinylchloride (PVC) jackets. Jackets include UV resistant with reinforcing wire for aerial suspension (-S) and standard.

AM systems can be designed to run approximately 3500ft of NF-2D cable or 1300ft of NF-1D in a single end-fed length. Double that length can be made with the addition of a splitter. LPB linear amplifiers can be added into the system to extend it without altering the RF signal. Typical reception distance is approximately 75-100ft on either side of the cable. LPB created what is believed to be the longest radiating coaxial cable system in the world, covering 22 miles along the Atlantic City Expressway in New Jersey (USA).

FM Stereo systems can operate with 100ft of NF-1D or 400ft of NF-2D in a single end-fed run. Again, double the distance using an RF splitter as well. Linear amplifiers are available to extend these distances as well. Typical reception distances are from 100-200ft on either side of the cable in stereo and about triple the distance in FM mono.

For both AM and FM applications requiring extremely long lengths of cable without the use of linear amplifiers, LPB can supply Andrew Radiax¨ radiating coaxial cable. A single LPB AM transmitter can feed 11000ft of Andrew Radiax¨ in a single end-fed run. Custom designs are a specialty for LPB engineers and greater length systems can be achieved.

Applications

LPB designs for radiating cable systems are limitless, and ever-increasing. Common systems include amusement park entry roads (for driver information), commercial information along roadways in front of individual stores or shopping centers, language translation systems, hearing-impaired systems, health club systems, etc..

Several major amusement parks and tourist attractions in the United States use LPB radiating cable systems along their entry and exit roads to inform motorists of the available activities, hours of operation, parking and weather information. One park includes a drive-thru safari in which the animals roam free around passing cars. Each animal area has a separate message zone broadcast to the vehicles, providing information on the habitat and animals as they pass. Careful engineering design and installation prevent interference between transmitters and message zones.

The Reverend Billy Graham uses up to seven LPB radiating cable systems to provide simultaneous language translation services to attendees of his Crusade worldwide. Audio is provided by a translator and patrons purchase inexpensive walkman-type receivers with headphones which allow them to listen to the service in their native language. Many other religious organizations also use LPB systems for simultaneous translation duties worldwide. These systems can be configured for multiple channels in AM and FM packages. LPB has designed heavy-duty touring packages for these applications.

Nearly 70 sports arenas in the United States have an LPB coaxial cable system suspended below the ceiling to rebroadcast the play-by-play for the game. Sports arena systems rebroadcast a local radio station, which has poor reception in the stadium. but has licensed the broadcast rights for the local team. These systems are growing rapidly in popularity as they are also very useful to the hearing-impaired, who are able to tune in the event and adjust the headphone volume to their necessary levels.

LPB Radio-Aide systems were developed for churches requiring either translation or additional services for the hearing-impaired. These are radiating cable systems for coverage of a main worship room and/or a large outdoor area designed to reach all of the seating in the designated area and permit all worshippers access. An extension of these systems has been a parking lot system, which provides church service rebroadcasts for cars, typically for the infirm or families with small children.

A common application for LPB FM radiating cable systems is in health clubs and gymnasiums. Many of the larger exercise rooms have multiple TV or video programs. Using FM transmission, LPB isolates the audio program of the videos so that only those wishing to hear them may do so (with a pocket radio) and those who are not following a video program are not disturbed by the excessive noise generated by the multiple audio programs. These systems are also used around indoor jogging paths to provide music and encouragement to runners.

LPB FM coaxial cable systems are in use at more than 30 US schools. These systems allow a college to operate an FM Stereo radio station without having a license from the FCC, and to contain the signal within the school property. These stations, like carrier current, provide the students with a broadcast experience and an outlet for their own music which might not otherwise be available in their market.

2.3 AM Vertical Antenna Systems (back to index)

The FCC permits licensed Travelers Information Stations (TIS) in the United States. These are short (49ft) antenna systems with a maximum of 10 watts input power and a coverage radius of approximately 4-6 miles. They are designed specifically to be used by federal, state and local governments to disseminate information on traffic conditions, weather and other necessary information to motorists. These systems are licensed only to government agencies and are commonly used at airports, highway intersections, national parks, and construction sites.

Although the rules may vary for these applications in other nations, the principal of these systems should be universal as they have proven very effective in the United States. By providing emergency traffic information and emergency weather information, these systems can assist in reducing traffic problems, moving large numbers of people to safety and alerting drivers well in advance of hazards.

Applications

TIS systems at airports provide incoming drivers with information on parking, passenger drop-off and pick-up, airline terminal locations and other information well outside the airport, this reduces the number of confused and misdirected drivers, thereby allowing for smoother operation of airport roadways and a more efficient flow of traffic. Use of multiple frequencies at an airport would permit specific flight information to be provided as well, if desired.

Although these systems are typically used with only 10 watts of input power, exceptions have been licensed for emergencies. In areas of the United States which are regularly subjected to severe weather conditions (hurricanes, flooding, etc...) there are a number of 100watt systems which operate only in case of an emergency (people are alerted to tune in via a loud siren). These systems are also in use around some of the nuclear power plants and other hazardous material sites in the US.

2.4 Tunnel and other Rebroadcasting Systems (back to index)

LPB engineers have provided designs for rebroadcast systems in motor vehicle tunnels throughout the world. LPB transmitters operate in tunnels in Europe and Asia, as well as the United States. LPB has provided equipment for tunnel systems as well as complete design and specification work, when needed. These systems are used either to rebroadcast local radio stations, or emergency information to vehicles in the tunnels.

LPB engineers have also designed systems for rebroadcasting in underground environments and/or construction areas with heavy RF shielding which would otherwise prohibit the use of radio communications. One of these systems will be installed in July 1997 in Taipei, Taiwan in an underground shopping mall which is currently under construction. The system will rebroadcast 10 FM radio stations and includes emergency override communications in the event that they will be required.

2.5 FM Vertical Antenna Systems (back to index)

LPB has created the FM ADvantage an FM Stereo, Frequency-Agile Limited Area Transmitter. Featuring a phase-locked loop, the frequency-synthesized, frequency-agile, FM Stereo transmitter is FCC Certified. The unit is set to frequency using a set of three rotary DIP switches located on the printed circuit board. The PLL design eliminates drift and temperature instability problems, which plague "kit" models. The transmitter is in a stand-alone housing for connection on the exterior to audio sources via RCA connectors. This is a fully agile transmitter capable of broadcasting from 87.9MHz to 107.9MHz with end user selectable frequencies. An LED indicator verifies frequency lock and stability.

The Part 15 field strength regulations will permit this system the same coverage field as the radiating cable systems - 250µV/m at 3m. This means that the FM ADvantage can reach radios up to a 200ft radius in FM Stereo and up to 3 times that distance in Mono. As with any low power system, the quality of the receiver and the availability of a good frequency will influence the coverage of the systems.

Applications

This new transmitter has a wide application base due to its ability to operate as both a fixed and mobile transmission device. It is configured in either AC or DC systems for fixed or mobile applications. In standard fixed-site AC mode, it will provide opportunities for use in Health Clubs, Language Translation, Hearing-Assistance, Real Estate, Business Advertising and many other areas.

In DC mode, it can be used with mobile business advertising such as tree surgeons, electricians, plumbers and any other business that relies on signage on a vehicle for attracting customers. Additional possibilities include use on highway construction or emergency vehicles. It can also be powered from DC battery sources and solar panels for DC operation in outdoor advertising. The applications for this product are nearly limitless, and grow with each discussion.

3.0 LPB Design Capabilities (back to index)

LPB has been engineering low power broadcast systems since 1960 - a longevity most other companies can only wish to obtain. From the world's longest radiating cable AM system to the Los Angeles International Airport Travelers Information Station (installed in 1972), LPB has created some of the most significant low power systems in the United States. LPB systems function as a training ground for future broadcasters in schools worldwide, and often serve the graduates in their new workplace.

LPB strives to ensure that the maximum effectiveness is achieved using their systems. For this reason, they review and offer engineering advice for their systems as well as worldwide technical support. LPB engineers and technicians are available for field consulting, site selection, technical support, maintenance and construction of low power systems worldwide. Low power systems are not simple to design and specify. Beware of radio consultants who offer their services for low power systems. This is a very specialized field and there are few with the experience and expertise required to design LEGAL and FUNCTIONAL systems. A knowledge of 2-way radio engineering does not qualify one to design a Travelers Information Station. LPB has the experience and understanding required to design the best systems for your budget. You can rely on LPB.