User talk:Ki7z

2012-11-30T20:59:18Z

Ki7z: Created page with "I would like to encourage everyone to add content and contribute to this wiki."

I would like to encourage everyone to add content and contribute to this wiki.

Loop antenna

2012-11-30T20:52:22Z

Ki7z: /* Large Loops */

There are two types of loop antennas: '''small loops''' and '''large loops'''. The key difference between the two is that in a small loop, the current is approximately in phase at all points around the loop, while in a large loops the phase varies at different points. The two types of antenna have very different properties and are used for different purposes.

== Small Loops ==

''Main article: [[small tuned loop]]''

A common saying in antenna design circles is "small, efficient, [[broadband]]: pick any two". As their name implies, small loops are small and reasonably efficient, but they are necessarily narrowband antennas. This means that even small changes in frequency require retuning the antenna.

[[Mobile antenna|Short linear antennas]], whether horizontal or vertical, have capacitive reactance and require an inductor for tuning. [[Small tuned loop|small loops]] are just they opposite; they have significant inductive reactance, and require a capacitor for tuning. Most [[Small tuned loop|small loops]] use a variable capacitor, allowing the antenna to be tuned over a wide range (5 MHz - 15 MHz is easily accomplished).

Small loop antennas have a perimeter of no more than 0.12 λ. (Remember that λ is the symbol for [[Electromagnetic Waves|wavelength]].) They are normally mounted in the vertical plane.

This type of antenna has very sharp [[nulls]] at right angles to the plane of the loop. These nulls can be very useful for suppressing [[QRM]] from a local source. Simply rotate the loop until the interference can no longer be heard. Because the [[nulls]] are sharp, small changes in antenna orientation can make a large change in signal or noise received from the direction of the [[nulls]]. The [[nulls]] are sharpest on the smallest loops (perimeter approximately 0.05 λ, and gradually broaden as the perimeter increases to 0.1 λ and beyond.

== Large Loops ==

Large loop antennas have a perimeter of at least 1/2 λ, but they develop significant gain when increased to 1 λ or 2 λ. Large loops are normally mounted in the horizontal plane.

[[File:skyburner.png]]

== Quads ==

[[Quad antenna|Quad antennas]] are essential multiple large loops mounted near each other, with one of them fed and the others used as [[passive elements]]. [[Quad antenna|Quads]] can achieve significant [[gain]]. They have more theoretical gain than the commonly used [[yagi|yagis]], but they're harder to build since they require significantly more room and are a bit more sensitive so many people just opt for building [[yagi|yagis]] instead.

{{antennas}}

File:Skyburner.png

2012-11-30T20:51:28Z

Ki7z: Large Loop (by KI7Z) Intended as a temporary until a better image is presented.

Large Loop (by KI7Z) Intended as a temporary until a better image is presented.

Amateur Radio Wiki - User contributions [en]

User talk:Ki7z

Loop antenna

File:Skyburner.png