How to Read an Antenna Spec Sheet
Antenna spec sheets provide the technical specifications most users are going to need in order to successfully use the antenna. Let’s review how to read an antenna spec sheet.
The title of the specification sheet should make it clear which antenna you’re dealing with. Who made the antenna? What model is it? What is the revision letter, if any?
Most antenna specification sheets give the key information about the antenna. What are its dimensions? How much does it weigh? What material is it made out of, if this matters to the user? What components are provided with the antenna? Some antennas are sold without any mounting hardware, while others are sold in an enclosed dome with connecting hardware.
Mounting and Connection Information
Connection information tells you how to connect coaxial cables or other wiring to the antenna. The wiring will either carry the signal your radio will generate to the antenna for broadcast or carry the signal the antenna receives to the radio.
Mounting instructions tell the owner how to mount the antenna so that surrounding hardware won’t interfere with its function. For example, an antenna may need to be pointed toward the intended signal or at a specific angle from the horizon in order to work well. Many antennas will have their electrical properties altered if it touches a metal support or another antenna. Too many antennas fail to work properly because someone drilled holes through it and damaged the tracing in an effort to put mounting holes in it before attaching it to a wood or metal boom.
Good mounting instructions will also tell you where to route the coax (coaxial cable) so that the wire carrying the signal doesn’t inadvertently impact reception or broadcast.
The antenna factor describes the required field strength that produces one volt at the antenna terminals. The antenna factor or AF is calculated by dividing the electric field strength by the voltage at the terminals of the antenna. This basic equation doesn’t take polarization mismatch loss into account.
If you were doing the analysis in decibels instead of standard units, the antenna factor is the electric field strength in DB/m minus the Voltage in dBV.
Antenna factors change along with the frequency, if the antenna sends over a frequency range. A good specification sheet will show you the antenna factors at regular intervals. The antenna spec sheet may provide a chart showing gain for all frequencies the antenna receives.
Antenna gain does reflect the antenna’s amplification of the signal. However, antenna gain is a metric that gives both the antenna’s efficiency and directivity in decibels. The higher the gain, the more focused the beam width. In theory, the antenna broadcasting equally in all directions would have zero dB gain.
Gain is different from the antenna’s transmission power; that is measured in watts and called the input power level limit.
Depending on the product and application, the specification sheet may include legal disclaimers. For example, it may say that you’re allowed to use the antenna for wifi or drone applications but warn that you may not be allowed to use a drone in specific locations. It could tell you the major uses of the frequency range the antenna receives but warn that it is illegal to listen in on others’ wireless communications without consent or advise that the antenna works on ham bands but you must have a ham radio license to broadcast yourself.