NAB asked the FCC to allow stations to use computer modeling to demonstrate that AM directional antennas perform as authorized.
In comments filed to MM Docket 93-177, NAB noted that a coalition of AM antenna experts, broadcast engineers and equipment manufacturers believes using moment method computer modeling will save stations engineering time and lessen the financial expenses of maintaining AM DA systems, as reported earlier in RW (see story here).
The AM Directional Antenna Performance Coalition, states NAB, has found that “proofs of performance are not necessary for arrays adjusted pursuant to moment method programs.”
NAB further stated: “It is common knowledge among industry professionals that field strength measurements are often inaccurate due to proximity effects, scattering and local electromagnetic environmental effects.”
In the past decade, computer modeling software has improved to the point that AM directional arrays are “easily adjusted without reliance on field strength measurements. Indeed, today’s modeling programs are sufficiently sophisticated to accurately predict radiation in critical directions toward other stations,” stated the trade group.
With the recent authorization of AM IBOC, AM stations have “out of necessity,” become capable of diligently maintaining and optimizing their directional antenna systems, according to NAB, which added that the proposed rules would provide needed relief, in terms of engineering manpower and financial resources.
NAB said, “The time is right for the commission to set aside inefficient antenna measurement requirements — many of which date to the 1930s — in favor of rules more suited to 21st century AM broadcasting.”