Javascript Electronic Notebook
VHF/UHF Yagi Antenna Design
by Martin E. Meserve

Contact Me | What's New | Site Map  

   Home | Antennas | VHF/UHF Yagi Antenna  

JavaScript®
Electronic
Notebook

Place your mouse pointer over any of the catagories above, for an active menu of their contents.

Click to view the
Resource Credits

Steves free web site templates

Page Top

Introduction

Frequency, Gain,
and Spacing

Boom Type
and Mounting

Element
Diameters

Design/Example
Viewing

Introduction

This page is a JavaScript® enhanced web page that implements the design of an antenna in the VHF, UHF, and Microwave frequency range with High Gain (11.8 to 21.6 dBd) and Long Boom Lengths (2.2 to 39 Wavelengths). Lower frequency antennas that have these attributes tend to be physically impractical. This page is adapted from BASIC program original written by Jerry Haigwood, KY4Z, and Bob Stein, W6NBI. This program is maintained by Ian White, G3SEK, and the master is now on his VHF/UHF Long Yagi Workshop page at www.ifwtech.co.uk/g3sek/diy-yagi/dl6wu-gg.bas.

For those that have already been through this page a time or two, and would rather not deal with the rhetoric, you might want to try my Yagi Quick Design page. One screen has it all.

Page Layout

There are 4 major sections, three for defining your design and one for viewing your design results. Navigation can be done by simply scrolling up and down the page, or you can use the menu that appears at the top of each major section.

Help Function

Once you get use to the sections, defining your design and inputting it into the data areas will be very straight foward and you won't need further explanations however, when you do, there is a Help page available that discusses each section in greater detail accessable through the section navigation menu. If you are not sure what the program is asking for, this should help.

Dimensions

You can choose to enter all you data in US/Imperial dimensions or Metric dimensions. You can also mix dimensions. For example, if you wish to specify Boom Diameter in Inches but want to use Millimeters to specify the element diameters, it's OK. The program takes care of the necessary conversion.

Error Notification

The text boxes, usually located under a set of select areas, contain information to aid in your data entry. Data inconsistant with this information is not brought to your attention until you display the antenna design in the Design View section. The antenna will still be designed, however, you will be notified of the inconsistancy and should realize that this data could cause eroneous calculations.

Page Top

Introduction

Frequency, Gain,
and Spacing

Boom Type
and Mounting

Element
Diameters

Design/Example
Viewing

Design Frequency, Gain/Boom Length, Reflector Spacing, and Director Element Spacing

On the right, define the Design Frequency for your antenna design. Then define either the Foward Gain or the Boom Length.

Gain should be between to 11.8 dBd and 21.6 dBd. Boom Length should be between 2.2 and 39 Wavelengths.

DL6WU used a 0.2 wavelength Reflector Spacing in his designs and the ARRL uses 0.15 wavelength Reflector Spacing in their designs. The spacing can be anything between these limits. The equations used for the Director Element Spacing is also slightly different between the DL6WU and ARRL designs. Select the spacing(s) of your choice but note that, it may affect the feed impedance.

x.

Design Frequency

Select Foward Gain or Boom Length

Reflector Spacing

Director Element Spacing

Page Top

Introduction

Frequency, Gain,
and Spacing

Boom Type
and Mounting

Element
Diameters

Design/Example
Viewing

Boom Type, Mounting, Dimensions, and Boom Correction

Select the type of Boom, metalic or non-metalic, and the method of mounting the elements. Then enter the Boom Diameter. The text area below will advise you of the limits that you should observe.

A x boom with x elements is currently specified with a diameter of x, which is x. A default Boom Correction of x has been calculated.

To accept the calculated Boom Correction, do nothing. However, you can choose a different Boom Correction. Use the Init BC Button to reset the Boom Correction to it's default, calculated, value.

Currently, x.

Boom Type (Mounting)

Boom Diameter

(At this frequency, the Boom Diameter should be limited to x, which is x)

Boom Correction

Page Top

Introduction

Frequency, Gain,
and Spacing

Boom Type
and Mounting

Element
Diameters

Design/Example
Viewing

Element Diameters

It is recommended that the element diameters be limited to between 0.001 and 0.02 wavelengths. At x, this is x to x, or x to x. The idea here is to keep the diameter small in relation to the element length. Thus, as frequency increases, the useful element diameter decreases.

Driven Element
Diameter

Parasitic Element
Diameter(s)

Page Top

Introduction

Frequency, Gain,
and Spacing

Boom Type
and Mounting

Element
Diameters

Design/Example
Viewing

Design/Example Viewing

Once all of the antenna requirements are defined, a output design page can be viewed, in US/Imperial or Metric dimensions. Once you have viewed the design and decide that you need to adjust the input parameters, navigate to the required section using the menu at the top, and then re-display. The view window can be left open and will update automatically, when the View button is selected.

The current design is an antenna for x. It has x Reflector, x Driven, and x Director Elements. Estimated Gain is x dBd.

For further viewing, below are several antenna designs from The ARRL Antenna Book, 18th Edition. They were designed using a method similar to the one in this web page, however, the element spacing and length curves are slightly different. That being said, don't expect to design an antenna with this program that exactly matches the ARRL designs. When you first click on one of the buttons a separate window will pop up. Clicking on the other buttons will then replace the contents of that popup window.

This is an antenna design for 144 MHz. It has 1 Reflector, 1 Driven, and 10 Director Elements. Estimated Gain is 12.5 dBd.

This is an antenna design for 222 MHz. It has 1 Reflector, 1 Driven, and 14 Director Elements. Estimated Gain is 14 dBd.

This is an antenna design for 432 MHz. It has 1 Reflector, 1 Driven, and 20 Director Elements. Estimated Gain is 17.9 dBd.

This is an antenna design for 432 MHz. It has 1 Reflector, 1 Driven, and 31 Director Elements. Estimated Gain is 19.9 dBd.

This is an antenna boom design example, by the ARRL, for obtaining extended boom lengths.