RF Frequencies 101

February 1, 2018 at 8:00 AM

 

RF, radio frequency, is an electromagnetic wave between 1 MHz and 3 GHz used in wireless networks to transmit video, voice and data. They can also be used for AM radio broadcasting, navigational beacons and shortwave radio. Waves from 3 GHz to 30 GHz are microwave frequencies used for FM radio, aviation communications, radar and satellite links. Millimeter wave frequencies range from 30 GHz to 300 GHz and are used to transmit large amounts of data and simultaneous voice or video. RF waves can be transmitted through different media such as coaxial cable, a circuit board or through an antenna.

 

There are three main factors to consider for RF waves: frequency, wavelength and Hertz. Frequency is the number of electromagnetic wave cycles that pass a specific point per unit of time. Wavelength is the distance after which the electromagnetic wave fields repeat themselves. Hertz is a measurement of the wave cycles per second.

 

           1 Hertz (Hz)              =      1 wave/ 1 second

                                           1 Kilohertz (kHz)        =      1 thousand waves/ 1 second

                                           1 Megahertz (MHz)     =      1 million waves/ 1 second

                                           1 Gigahertz (GHz)      =      1 billion waves/ 1 second

 

To get the full picture, and for a handy reference, here is a chart of RF frequencies:

 

 

For more information on RF frequencies used in wireless networks, check out some of our other blog posts: RF Antenna FAQs and Wireless Infrastructure 101.

 

RF Antenna FAQs

June 22, 2017 at 8:00 AM

 

 

Antennas are critical components to any wireless network, so having a good grasp of antenna technology can be very important for anyone engineering, designing or managing a wireless network. With so many antenna options and so much information to digest, it’s no wonder people have a lot of questions when it comes to antennas. Here, we’ll highlight some of the questions we’re asked most frequently.

 

How do I choose the correct Wi-Fi antenna? 

There are two main types of antennas - Directional and Omni-directional:

          

-   Directional antennas emit an RF signal in a focused beam, like how a car headlight focuses light in one direction. They are great if your application is a  point-to-point Wi-Fi link. For example, if you’re transmitting a signal from one building to another, you would use a directional antenna.

 

-   Omni-directional antennas radiate an RF signal in a 360-degree pattern. These antennas are ideal if you need the Wi-Fi signal to cover a 360-degree radius.

       

-   If you have a point-to-multipoint application, such as a campus environment, using a combination of directional and Omni-directional antennas would be your best bet.

 

What is antenna polarity?

Antenna polarity is the orientation of the radio wave’s electric field with respect to the Earth's surface. Antennas can be vertically polarized, horizontally polarized or a combination of the two. For more information, check out our antenna polarization blog post.

 

What is antenna gain? 

Antenna gain is a relative measure of an antenna’s ability to direct or concentrate radio frequency energy in a particular direction or pattern. Antenna gain is typically measured in dBi or dBd. Click here for more info.

 

What is 802.11? 

802.11 is an IEEE standard for implementing wireless local area network (WLAN) communications in the 2.4, 3.6 and 5 GHz frequency bands. There are numerous 802.11 standards and new versions continue to be developed. Existing standards include 802.11a, 802.11b, 802.11g, and 802.11n, 802.11ac, 802.11ac Wave 2, 802.11ah, 802.11ax, 802.11ay and 802.11af.

 

What is a decibel (dB)? 

A decibel (dB) is a unit of measurement for the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale. Decibels are commonly used in radio and sound measurement. One decibel is 1/10 of a Bel.

 

What is dBi ? 

Decibels-isotropic (dBi) are decibels relative to an isotrope. This unit of measure defines the gain of an antenna system relative to an isotropic radiator at radio frequencies. 

 

What is an isotrope? 

A theoretical isotrope is a single point in free space that radiates energy equally in every direction, similarly to the Sun.

 

What is frequency? 

Frequency is the number of cycles of alternating current in one second. It is measured in hertz (Hz).

 

What is a microwave? 

A microwave refers to all radio frequencies above the 1 GHz range. They are shorter than normal radio waves but longer than infrared radiation. Microwaves are used in radar, communications, for heating in microwave ovens and in various industrial processes.

 

What is multipath interference? 

Multipath interference is when signal reflections and delayed signal images interfere with the desired, un-delayed, larger signal. It causes picture ghosting in over-the-air analog TV and errors in digital transmission systems.

 

What is path budget?

Path budget is a mathematical model of a wireless communications link. It takes into account a wide variety of factors that can affect operating range and performance. Path budget is sometimes referred to as "link" budget.

 

What is path loss? 

Path loss is the weakening of a signal over its path of travel. This can be caused by factors such as terrain, obstructions and environmental conditions. It is measured in decibels.

 

What is fade margin? 

Fade margin is the loss of signal along a signal path caused by environmental factors such as terrain, atmospheric conditions, etc. It is measured in decibels.

 

What is a point-to-point network? 

A point-to-point network is a communications channel architecture that runs from one point to another. Directional antennas would be used in a point-to-point wireless link.

 

What is a point-to-multipoint network? 

A point-to-multipoint network architecture runs from one point to several other points. For this type of network, you would use both Omni-directional and directional antennas.

 

What is radio frequency? 

Radio frequency (RF) is typically a frequency from 20 kHz to 100 GHZ. RF is usually referred to whenever a signal is radiated through an enclosed medium, like a transmission cable or air.

 

What is a radio wave? 

A radio wave is an electromagnetic wave of a frequency used for long-distance communication. It is a combination of electric and magnetic fields varying at a radio frequency and traveling through space at the speed of light.

 

What is very-high frequency? 

Very high frequency (VHF) is the designation for radio waves in the range of 30 to 300 MHz.

 

What is ultra-high frequency? 

Ultra-high frequency (UHF) designates radio waves that are in the 300 to 3,000 MHz range.

 

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