National Association of Broadcasters Engineering Handbook, 11th Edition

Chapter7.10

AM Diplexing, Combining, and Filter System Design

Ronald D. Rackley, P.E.

du Treil, Lundin & Rackley, Inc.

Sarasota, FL

Introduction

Combining transmitter sites of AM radio stations, commonly referred to as diplexing, has become an increasingly popular trend in recent times. Factors that militate toward multi-frequency operation at transmitter sites include the economy to be realized through savings in antenna tower and land costs, the difficulty with which new transmitter sites must be approved by regulatory authorities other than the FCC, and the common ownership of multiple stations serving the same markets.

The history of combining AM transmitter sites goes as far back as the 1930s. It was not uncommon to have stations share antenna ...