Saturday, March 26, 2011

Lesson 32: General Class Exam Course G9C

Here is lesson 32 which deals with directional antennas.  This lesson primarily works with three type of directional antennas: Yagis, Cubicle-Quads, and Delta-loops.  The video for this lesson is long, but the information is relatively easy to absorb.

The basic Yagi antenna consists of three elements: The driven element, reflector element, and the director element.  The driven element is the element that is connected to the feedline and thus the transceiver.  The other elements are what are called "parasitic" elements and their function is to focus the signal to and from the driven element.  By increasing the length of the Yagi and adding director elements, the gain of the Yagi is increased in the Yagi's focal direction.  The length of a Yagi's driven element is generally 1/2 wavelength of the desired frequency.

Cubical Quad antennas are the second directional antenna this section deals with.  The basic quad antenna consists of a driven element and a reflector.  Directive elements can be added to increase gain.  The driven element of a quad antenna equals a full wavelength of the desired transmit frequency.

Delta-loops are similar to quads except that they are triangular vice square.

A few points to memorize: The gain of a 3 element Yagi, 2 element quad, and 2 element delta-loop are all about the same.

The relative gain of a Yagi antenna in its focal direction is 9.7 dBi.

And that's about it.  As always, please leave any comments, suggestions, or questions in the comments box.  Thanks!


1 comment:

  1. Hi! It appears that the answers listed in the Exam Answers for this section do not align with the 21 questions covered in ths lesson.


    Ron F.