Giving Boosters Their Best Shot
Why have we focused on boosters to improve FM signal quality and listenability?
Once upon a time, broadcasters used Single Frequency Networks and FM on-channel booster sites with relatively high antenna heights to fill in areas where their main signal was blocked by terrain.
While the single site, tall tower booster did fill in the terrain blocked area, it often created interference with the main signal in areas that were covered by both the main and booster signals.
Taking advantage of new advancements in technologies, ten years ago we committed significant research and development to combine radio and cellular technology and enable FM Broadcasters using boosters to enhance their signals by reducing multipath interference between the main and booster transmissions through the use of a cluster of low to the ground, high power, highly directionalized synchronized booster sites.
We dubbed the commercialization of this technology MaxxCasting™ and built it to greatly reduce or eliminate, to the listener, this simulcast interference problem.
Yes, MaxxCasting is an FM SFN repeater system, but that’s where similarity ends.
MaxxCasting brings our new technologies to SFN repeater networks to resolve performance issues, including research into parameters that determine simulcast interference and advance geographic tools to intelligently design repeater networks.
MaxxCasting can calculate coverage, population, automotive traffic, signal levels and interference areas, deducts total population factoring interference areas, including buildings as well as terrain.
It has been deployed nationwide and will serve as the foundational architecture for ZoneCasting™, which is the geo-targeting of broadcast content based on the geographical location of the receiver.
The MaxxCasting system deploys “zones” within a defined service area of a primary (main) FM broadcast transmitter. These zones can contain one-to-n number of on-channel, same frequency booster transmitters that broadcast in a simulcast (synchronized) manner. The design of the zone is such that the synchronized booster transmitter(s) comprising the zone create a signal (and RF field density) over the intended coverage area for that zone which is significantly higher than the main transmitter signal.
By deploying multiple synchronized transmitters in the desired coverage zone with lower antenna radiation heights, the coverage radius of each booster is reduced, thereby decreasing the interference area with the main transmitter.
Typical MaxxCasting™ System
GBS continues to work with and seek feedback from the radio industry, including NAB’s Radio Technology Committee. The research of GBS and the verification of the technologies was completed by NPR Labs in 2013. It was further aided by the studies conducted by the respected Dr. Ellyn Sheffield at Towson (Md.) University’s notable radio/audio department with over 20,000 samples of audio listened to and rated. The resulting findings included the thresholds of listener acceptance or rejection of audio samples recorded at various interference levels and using various genres of music and talk formats including voice over plus mono and stereo reception.
The results form a core GBS design formula, along with some highly intelligent software programs, to predict coverage and minimize interference to present a far improved implementation of an SFN.
In every MaxxCasting system deployment, many field strength readings are taken to verify coverage and optimize its computer design simulations. By deploying multiple synchronized transmitters in the desired coverage zone with lower antenna radiation heights, the coverage radius of each booster is reduced, thereby decreasing the interference area with the main transmitter.
In addition, by deploying the booster transmitter antenna radiation centers at lower heights, the reduction of the booster signal as a function of distance is generally greater than the main transmitter, also reducing the potential interference area.