Loop Antennas

  

 

A loop antenna is a radio antenna consisting of a loop (or loops) of wire, tubing, or other electrical conductor with its ends connected to a balanced transmission line. Within this physical description there are two very distinct antenna designs: the small loop (or magnetic loop) with a size much smaller than a wavelength, and the resonant loop antenna with a circumference approximately equal to the wavelength. Self-resonant loop antennas are larger. They are typically used at higher frequencies, especially VHF and UHF, where their size is manageable. They can be viewed as a form of folded dipole and have somewhat similar characteristics. The radiation efficiency is also high and similar to that of a dipole.
 
Small loops have a poor efficiency and are mainly used as receiving antennas at low frequencies. Except for car radios, almost every AM broadcast receiver sold has such an antenna built inside of it or directly attached to it. These antennas are also used for radio direction finding. As the frequency or the size are increased, a standing wave starts to develop in the current, and the antenna starts to have some of the characteristics of a folded dipole antenna or a self-resonant loop. A technically small loop, also known as a magnetic loop, should have a circumference of one tenth of a wavelength or less. This is necessary to ensure a constant current distribution round the loop. 
 
The large or self-resonant loop antenna can be seen as a folded dipole which has been reformed into a circle (or square, etc.). This loop has a circumference approximately equal to one wavelength (however it will also be resonant at odd multiples of a wavelength). Compared to the dipole or folded dipole, it transmits less toward the sky or ground, giving it a somewhat higher gain (about 10% higher) in the horizontal direction.
 

 

 

News

Cerebrum: Mobile Passwords Lifted Acoustically with NASB

Hackaday Cerebrum: Mobile Passwords Lifted Acoustically with NASB Hackaday The prototype was tested by interfacing a magnetic loop antenna directly onto the Cerebrum through a coax-to-marshmallow transition. By...

Apr 1, 2017

Loop Antenna is Portable

Loop Antenna is Portable Hackaday We don't know if [OH8STN] has a military background, but we suspect he might since his recent post is about a “DIY Man Portable Magnetic Loop Antenna .” “Man-portable” is usually a...

Feb 26, 2017

Analyst Angle: Closed loop antenna tuning saves the smartphone from poor performance

RCR Wireless News Analyst Angle: Closed loop antenna tuning saves the smartphone from poor performance RCR Wireless News Modem suppliers that implement advanced closed- loop antenna algorithms will be able to...

Jan 11, 2017

Young Ham Wins First-Place Science Fair Trophy with Mag Loop Antenna Entry

ARRL Young Ham Wins First-Place Science Fair Trophy with Mag Loop Antenna Entry ARRL A 10-year-old ARRL member from Snoqualmie, Washington, took first place in his grade and division for a magnetic loop antenna...

Apr 27, 2016

A VETERAN'S STORY: The Ghost Liberator — Lady Be Good

Warbirds News A VETERAN'S STORY: The Ghost Liberator — Lady Be Good Warbirds News The actions of pilot in flying 440 miles into the desert are indications that the navigator probably took a reciprocal reading off...

Apr 24, 2017

LeEco Le 2s leaked photos hint at ultra-thin bezels, loop antenna design

BGR India LeEco Le 2s leaked photos hint at ultra-thin bezels, loop antenna design BGR India LeEco Le 2s leaked photos hint at ultra-thin bezels, loop antenna design. LeEco is reportedly gearing up to launch the Le...

Aug 16, 2016

Building a magnetic loop antenna and broadband amplifier for your SDR

Building a magnetic loop antenna and broadband amplifier for your SDR Southgate Amateur Radio Club In this guest post, Dave Gahimer, K9ZCE, describes how you can build a compact (dual) magnetic loop antenna to improve...

Mar 27, 2016

DX Engineering Acquires InLogis, Exclusive Rights to Make and Market Active Magnetic Loop Antenna

DX Engineering Acquires InLogis, Exclusive Rights to Make and Market Active Magnetic Loop Antenna ARRL DX Engineering of Tallmadge, Ohio, has acquired the assets of InLogis and the exclusive right to manufacture and sell...

Nov 24, 2015

Amplified Loop Antenna LA800

Officer.com Amplified Loop Antenna LA800 Officer.com AOR USA has added a highly sensitive and directional “ loop” antenna to its product line. The LA800 is designed for outdoor use by monitoring enthusiasts. It...

Dec 5, 2013

Magnetic Loop Antenna controlled by Arduino and infrared

YouTube Magnetic Loop Antenna controlled by Arduino and infrared YouTube This video presents a Magnetic Loop antenna controlled by an Arduino. The controller system receives a command via infrared transmitter...

Oct 16, 2012

Units & Modules