Transmitter Efficiency: Overview

The purchase of a new transmitter is among the most important technical decisions that can made by a broadcaster. This is particularly true today, due to rising energy costs and recent technological improvements in high efficiency amplifier designs. In some cases, the purchase of an energy-efficient transmitter may even pay for itself over time, particularly if care is taken to design as energy-efficient a transmission system as possible.

The Transmitter Efficiency Calculator is a tool that predicts transmitter system energy costs both for present operations and for the "what if" evaluation of prospective, future purchases. You can apply the actual, measured efficiency of your current transmitter (if available), the efficiency specifications procured from the manufacturer, or the published efficiencies of new transmitters that you may be considering. Additionally, the tool can predict the overall efficiency of typical installation configurations while considering local climate, energy costs, HVAC, and, in the case of digital FM transmission, various IBOC combining methods.

Efficiency Calculator: Introduction

The Transmitter Efficiency Calculator can quickly and easily approximate transmitter site power consumption and costs based on the answers to several simple questions. The first group of questions relate to the broadcast transmitter configuration. A second group pertains to location (to estimate regional climate and state commercial power costs), the building, and site air- conditioning (if any).

Help is available by moving the mouse pointer over the question-mark symbols associated with each question. When all questions have been answered, estimated power consumption and cost results will appear.

This Calculator's strength comes from consistent and repeatable results. Therefore, while the assumptions and simplifications may impact bottom-line accuracy, results are believed valid when making “what if” comparisons of different transmitters and scenarios.

There are some limiting factors inherent in the Calculator that should be noted:

The database that serves as the engine for the Calculator utilizes data provided by equipment manufacturers and is by no means complete. As an example, there is presently no manufacturer-provided data available for VHF television transmitters.
Most of the manufacturer-provided data is for current makes and models.
For the efficiency calculations, the manufacturer’s stated efficiency of the transmitter is used, no matter the power output selected. Therefore, if a 20 kW transmitter is rated as 88% efficient, and it is being operated at 10 kW, the Calculator makes the assumption that the transmitter is still 88% efficient at 10 kW, which may not be the case.
More accurate results can be achieved by using actual, measured AC-to-RF efficiency.

Additionally, a number of assumptions have been made, including, but not limited to, the following:

A typical air-conditioner efficiency (SEER=10) is utilized to determine HVAC power consumption. Actual efficiency may vary.
Due to wide variations in heating fuel types, fuel costs, and heating system configurations, the cost of heating was ignored.
Only one radio or television transmitter is located in each building.
The transmitter building is located on a ground-level, concrete slab.
Roof insulation has the same R-value as wall insulation.
FM IBOC stations using high-level combining have a 10 dB combiner. Other combiner types will result in more or less reject load heat, which may become a factor in cooling calculations.
If transmitter heat is exhausted, 85% of the transmitter’s heat leaves the building.
Climate considerations are based on historical records of monthly heating and cooling degree-days, which, in turn, are based on daily mean temperatures. While these estimates consider the regional differences in climate, they are not known to be precise.

In order to make the Calculator simple to operate, dozens of assumptions were necessary. While the Calculator’s results are believed to be reasonable, it is important to stress that far more accurate results can be achieved by conducting an exhaustive energy audit.

I have read the foregoing and agree that the calculator is being used as an additional tool in measuring energy efficiency, and that neither FASTROAD nor NAB makes any warranty or guarantee of accurate results from the use of this calculator.