How To Exchange Antennas on Power Meter

WiPry-Combo’s versatility is highlighted in this post. Customize WiPry-Combo for any measurement setup where a peak power meter would be used. In the picture above there are three types of antennas. The frequency of operation and typical application are discussed in this blog post. To see an example of WiPry-Combo connected to a custom antenna, check out this blog post.

Antennas for nearly any application

One of the key elements of using WiPry-Combo’s broadband peak power meter is the input configuration. A conducted measurement configuration has WiPry-Combo’s SMB port connected directly to the signal source through a coaxial RF cable. For over-the-air (OTA) testing, however, the appropriate choice of between-series adapter makes the wide range of commercial antennas available to WiPry-Combo users.

Antennas are characterized by their operating frequency and power rating

Antenna selection is based primarily on the operating frequency, or operating frequency span frequently called the 3 dB (half power) bandwidth. The operating frequency and physical dimensions are related by the following equation:

Example Antenna #1: 146/446 MHz Dual Band Mobile Antenna

The antenna in the green, plastic envelope (from the image above) is a high power dual band antenna used by HAM radio operators. The antenna works for two frequencies: 440 MHz (60 centimeter band) and 146 MHz (2 meter band). A dual band antenna like this one uses an inductive “choke” element to create an electrical partition for the two frequencies. The antenna resonates at the 146 MHz wavelength, using the entire length of the antenna, and at the 440 MHz wavelength using only half the length of the antenna. Also, this antenna structure is made of a heavy gauge conductor in order to withstand the high power associated with this application.

Example Antenna #2: AM Radio Band Antenna

The loop antenna, at the far left of the picture, is used with an AM broadcast radio receiver. The table below lists the frequency spectrum allotted by the FCC for AM radio stations. Compared to the other frequency spans, the nominal antenna length is much, much longer to meet the quarterwave or halfwave resonance criteria.

Example Antenna #3: 2.4 GHz Antenna

The white, circular antenna in the lower right part of the picture is used for connecting a desktop PC to a local area network over Wi-Fi. The operating frequency for this antenna and network is 2.4 GHz, nominal. The wavelength and corresponding halfwave and quarterwave lengths are just an inch or two. One trend with RF and microwave transmissions is this: higher frequency operation makes the physical dimensions smaller, but it’s more expensive and less efficient for power.