Yagi Calculator by John Drew,
VK5DJ
to develop DL6WU style yagis for VHF/UHF
Yagi Calculator is a Windows program to produce dimensions for a DL6WU style long Yagi antenna. Long yagis are commonly used from the 144MHz amateur band to the 2.4GHz band. The DL6WU yagi is highly regarded as being easy to build with repeatable results, broad bandwidth and a useful pattern.
The program on this site was developed in the early 90s as a DOS program. Time moved on and so did operating systems, so the 2003 version was an opportunity to convert to a Windows environment and update the information and modify some of the algorithms. In Sept 06 and 5 May 2007 I made very minor changes to labels and display. The latest version is 2.3.3 (4 December 2007) when I added the capacity to print the Balun details and semi-auto configure some element sizes in the "Design Yagi" screen. There have been recent minor fixes to ensure the program found images and the help files reliably. "Show yagi details" screen now returns to "Yagi Design" screen. No changes were made to algorithms. If you run Vista I recommend you run it as Administrator.
Example printout of a 2M design
Features of the free but copyrighted program include: calculation of the element length and element spacings of a yagi for a particular frequency, different size materials for boom and elements are catered for as are different methods of mounting, dimensions of baluns are calculated, there is provision for entering the dimensions of an existing DL6WU antenna for optimisation through an external program or to gather information on its gain, beamwidth etc. A handy SWR calculator and feedline loss calculator are included as part of the package. Stacking information is also provided as are estimates of gain. A helpfile is included that covers many aspects of yagi design as well as helping with the operation of the program.
Amateur and commercial manufacturers have made use of the Yagi Calculator to create effective yagi antennas. The examples below are of yagis built using the program and constructed by a non technical person to solve a communication problem in a commercial environment. I have shown this as an example of the non critical nature of the antenna.
A DL6WU design yagi solves a comms problem A home built 860MHz yagi is used by a local water conservation authority to provide data communications via a mobile phone network. The commercially provided antenna wasn't good enough for reliable communication. Telemetry from sensors gauge water depth and salinity. Each day the site is accessed by mobile phone (CDMA network) to determine the results from the previous 24 hours. Conventional omni directional antennas were not reliable as the sites are all low lying, often surrounded by scrub and usually many kilometres from a mobile phone cell. The yagis were built from a design by Yagi Calculator. The yagis were built on a fibreglass rod boom normally sold for use with electric fences. A 3 metre rod costs about $8. The elements are 3mm brazing rod. push fit in 3mm holes. The driven element is a single dipole, split into a channel cut in the fibre glass, fed with 50 ohm foam coax with a quarter wave sleeve balun. The element and balun assembly are fixed using an epoxy product called "Knead it". The pictured yagi was built by a person with no previous experience following conversations with nearby radio amateurs. |
 View of site |
 |
The yagi is shown at the top of a 5 metre pole aimed at the nearest CDMA phone site 30km away. The photo at right gives a good idea of the problem in gaining good signals at the low lying and wooded site. |
 |
A successful yagi built using a fibreglass boom and 'knead it'. I've suggested
the builder uses silicone to seal the material as it looks porous.
Download Yagi Calculator
Click link to download. This setup file is approximately 600K , run it to
install Yagi Calculator (Version 2.3.3)
Acknowledgements
Yagi Calculator is a program to assist with the design of long
yagi antennas. It uses the broad principles developed by DL6WU and printed
originally in the German Radio Magazine VHF Communications (March 1982).
The article was titled Extremely Long Yagi Antennas.
The work of David VK3AUU (AR Feb 1988)
in developing some equations to fit DL6WU's graphs was very valuable. The
reflector calculations are based on a Basic program written by KY4Z and W6NBI
and
with suggestions
by DL6WU. The ARRL Antenna Handbook
provided information, as did various sources on the Internet. K5OE's site
at http://members.aol.com/K5OE is a particularly useful one.
The author acknowledges the 1998 ARRL Handbook for information on coaxial
cable impedance, dielectric and velocity factor.
Yagi builders are reminded that DL6WU designs are primarily for long yagis.
A boom length of 2 wavelengths (or 10 elements) would be a minimum sized
antenna. On the other hand, yagis with as few as 8 elements have used the
design and worked very well.
Yagi Calculator offers some information for the construction of folded dipoles.
A folded dipole is the radiator of choice for many constructors.
A look up table for coax cables is provided and when a coax is selected
a 4:1 balun is calculated. A pictorial description is also provided.
There is provision to calculate the gain of a yagi of this design using an
input of boom length. This is because gain is almost independent of the number
of elements (for common designs).
Yagi Optimiser (YO) is commonly used to fine tune designs. This program allows
an experimenter to measure an existing beam and enter the dimensions for
the production of a .YAG file.
Note that it is NOT generally useful to try to optimise these yagis as you lose some of the strengths of the DL6WU design - these include easy, non critical construction, good gain and pattern and good bandwidth.
Providing that the design is derived from DL6WU then the elements may be
converted to and from categories of:
· Through and electrically connected
to a metal boom
· Through but insulated from a metal boom
· Either
attached to a non-metallic boom or well away from it
This means that a beam of one construction can be translated into one of an alternative construction and observations made on changes to element lengths. In addition it enables use by a yagi optimising program that can only use one or the other construction.
A YO file is generated on demand.
Optimised yagi files can be reloaded into the Make YO File page if required. (See the File menu when in the Make YO File page.) Only simple YO files as generated by Yagi Calculator and YO can be reloaded. The software does not cater for element taper or multiple frequency input.
Stacking pairs of yagis is a common strategy to improve results. The program offers a solution for stacking distance. It also calculates the estimated gain advantage. A SWR calculator is provided for those who measure forward and reflected power; it takes into account coax losses.
Links
Some valuable comments on scaling and boom diameters from W4RNL
Considerations on the effects of boom diameter by Lief Asbrink, SM5BSZ
Construction of a DL6WU yagi using a folded dipole by Jim W6PQL
Experiments on an antenna range by Jim W6PQL