Most Popular Articles
FM Antennas: The Silent Component
If you were to consider for a moment the question: "What is the most important part of the transmission system?" likely the first answer you'd come up with is "the transmitter." That's not really true, though, is it? The STL, the transmitter, transmission lines, and the antenna are all equally important. With the failure of any one of those, your station will be off the air. I'll focus on the FM antenna in this installment, and in doing so I'll consider three separate scenarios that would prompt you to buy a new one: the installation of a new main antenna, the installation of a broad-band antenna as part of a back-up system, and a low-power booster (or translator) antenna.
There are many questions to be answered before purchasing an antenna; some are the same no matter which of the three scenarios are being considered, and some are of course specific to the scenario. Here are some common questions:
■ What is the required effective radiated power (ERP)?
■ What is the available transmitter power output (TPO)?
■ What are the necessary downward radiation characteristics?
■ What is the necessary polarity (i.e., circular, vertical, horizontal)?
■ What is the available space on the structure?
■ How high will the antenna be above the ground?
■ Will the structure have the strength to hold the antenna in all conditions?
So, as you can see, some amount of research needs to be done even before you issue any kind of a request for quotations. Let's consider these questions in more detail.
Replacing an old antenna
The ERP vs. TPO question is easy to answer in the event that you are simply replacing an old antenna, and not changing transmitters. As an example: If you needed 17.5kW TPO for 50kW of ERP (with the old antenna power gain of three, and accounting for transmission line loss) then likely you'll be getting a new antenna with the same amount of power gain and similar physical characteristics, such as the amount of space needed on the tower. In this event you would still want to make sure that the weight and wind-load characteristics of the new antenna are acceptable for the tower, and that the downward radiation characteristics are the same or better than the old antenna.
- continued on page 2
Acceptable Use Policy blog comments powered by Disqus
[an error occurred while processing this directive]
Today in Radio History
The history of radio broadcasting extends beyond the work of a few famous inventors.
Read each issue online in our Digital Edition Format in your Web browser.
EAS Information More on EAS
The feed provides feeds for all US states and territories.
Need a calendar for your computer desktop? Use one of ours.
Information from manufacturers and associations about industry news, products, technology and business announcements.
When Northern Community Radio set out to build a new community radio station in rural northern Minnesota 38 years ago, naysayers said that it would be broadcasting “only to a bunch of gophers
Browse Back Issues[an error occurred while processing this directive]
Also in the July Issue
- Trends in Technology: Robust IP STL
- LPFM on The March
- RF Engineering: Modern Modulation Techniques
- Field Report: Tascam TH-2000 Headphones
- Battery Maintenance: Testing and Charging