VHF/UHF Yagi Antenna Design
by Martin E. Meserve
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Antennas | VHF/UHF Yagi Antenna
Place your mouse pointer over any of the catagories above,
for an active menu of their contents.
Click to view the
Frequency, Gain,and Spacing
Boom Typeand Mounting
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
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.
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.
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
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.
You can choose to enter all you data in
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.
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.
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.
Select Foward Gain or Boom Length
dBd - Foward Gain
inches - Boom Length
mm - Boom Length
Lambda - Boom Length
0.20 - DL6WU
0.15 - ARRL
Director Element Spacing
Use DL6WU Element Spacing
Use ARRL Element Spacing
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.
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.
Boom Type (Mounting)
Metal Boom (Bonded)
Metal Boom (Insulated)
(At this frequency, the Boom Diameter should
be limited to x, which
It is recommended that the element diameters be limited to between
0.001 and 0.02 wavelengths. At x,
this is 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.
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 Driven, and
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.