Monthly Archives August 2007

KnowledgeQuest – Yagi Antenna Design

Experiment with Yagi designs on your computer!

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There are many software packages on the internet useful in designing various types of antennas. I’ve been playing with a software package named “YagiCad 4.1” since about 1992. I first installed a copy of it on our TEARA webpage back in late 1994. Since then, I’ve received many emails from users of this software who praised it’s performance and simplicity. Here, many years later, I find myself updating this website with ‘work-arounds’ and tips, as the user base continues to grow. Seems the software’s author has developed quite a following!

Yagicad 4.1 was written by Paul McMahon VK3DIP. It’s shareware, so you can download it (and lots of antenna profiles) below. It’s a DOS program and can be run outside of windows if you like. It requires a minimum of a 386 PC platform to run and a math co-processor really speeds things up, but isn’t required. The program runs best in DOS (‘real DOS, not the fake stuff rolled up inside of WIN95/WIN98/NT, hehehe) or when executed from WIN3.x, but there are simple ‘work-arounds’ for 95/98/NT users. As computers and operating system have become more complex, users have come up with methods of keeping Yagicad4.1 running. Despite a little bug with newer operating systems, I LOVE this program and have designed/built many antennas with it. I’ve used a lot of other programs, but find myself back using VK3DIP’s YagiCad 4.1.

Hey, this is a great reason to drag out one of those older PC’s you’ve had packed away, trying to figure out a ‘real use’ for it! I used to toss everything that wouldn’t run on my newer computers, but have since discovered there were MANY great programs that were somewhat simpler to use and developed for the older PC platforms. Don’t automatically discount software just because it won’t run well on your newest machines or operating systems. Anyway, c’mon and lets get started with YagiCad 4.1!

Download YagiCad 4.1 here. This file will download as Once the download is complete, unzip the file into an empty directory. To start the program, type yagi41 from the dos prompt (first, switch to the yagicad’s working directory) or double click on yagi41.exe from your file manager in windows. First, before trying to start and run this program, read the rest of the notes and tips below.


1- Keep the .yag file names exactly 7 characters long (not counting the extension). Example: 1234567.yag or WB4IUY1.yag , etc. Since I didn’t write the source code for this program, I can’t explain why it grumbles over files names of other lengths. When running on older systems with Win3.1 or just DOS6.22 (or lower), you can name the files in any length you like, but WIN95/98/NT etc only allows file names of 7 characters long to be opened. Windows NT is especially finicky about this. Since you may wish to send me your files to add to this page, share with others, or maybe run Yagicad on a newer operating system in the future, I’d recommend always naming them 7 characters long. Simple fix. Also, if you download a file somewhere with a name of a different length, simply rename it to something 7 characters long, and you’re set. Easy!

2- When you design or modify antenna designs, you’ll want to give them a unique name (so you’ll know what they are!). Never use more than 60 characters (spaces included) in the NAME/TITLE or COMMENTS sections. No problem, another easy work-around.

3- NEVER us a COMMA (,) in the NAME/TITLE or COMMENTS sections. It’ll keep your work from opening later, and sometimes crash the program. Yet another easy work-around.

4- When used with WIN95/WIN98, Yagicad will only display/open the first antenna file (.yag files) it finds, when they reside in the same directory as the program. It doesn’t do this when running under DOS or 3.1 and earlier systems, and works OK on Windows NT…go figure, heheheheeh. If that should ever happen to you, I recommend you make a directory named ‘yagicad’, and a subdirectory called ‘template’. Once you unzip the file contents into the ‘yagicad’, move all of the .yag files into the ‘template’ subdirectory. Only move the file you’re going to model from or look at into the ‘yagicad’ directory. In nearly EVERY instance of a user having problems with WinNT, Fix #1 above solved it.

I’ve not found any other oddities when running Yagicad on newer computers with WIN95/98/NT. Should any of you run across other glitches, or come up with a better ‘fixes’, please drop me a note to [email protected].

The program has all the help files contained within, and can answer most questions. It will allow you to design a basic antenna based on a NBS antenna standard, and then scale it to your desired frequency. You can then modify element diamaters, boom length, match type, element spacing and lengths, etc. You can also generate E and H plane radiation plots. All data can be sent to a local printer. You can save your designs once complete.

Yagicad 4.1 comes with a host of sample antenna designs, thus allowing you to use a working design and simply scale it to your operating frequency. You can add or subtract elements, compensate for different element diameters, conductive or non-conductive booms, etc. A word of warning, however… When you open a sample antenna, click on “create” and name the antenna session to your own unique file name BEFORE you make changes (scale it, etc). Otherwise, your sample antennas will be forever modified. Remember, when you name a file, use 7 characters as outlined in Note #1 of ‘NOTES FOR WIN95/98/NT USERS’ above.

Once you’ve designed/modified your antenna, go to “calculate”, select “auto”, and then select “resonate”. Set a residual reactance of 0.0 ohms. This step of the program will alter the driven element to be resonant at your target frequency. If the Actual “Z” (impedance) is not approximately 50 ohms, go to “edit” and move the location of the driven element back and forth on the boom a little and then resonate the driven element again. Continue this process until the actual Z is about 50 ohms.

You can add files that you and others design to your library for future reference. You can also store the designs of commercially manufactured antennas in your library and scale to other bands later. Below is a list of the supplied antenna designs (to replace yours when you forget tip #1 above, hehehe), and a few others I’ve added. If you scale or design any antennas of your own, send me a copy of the .yag file and I’ll include them here for others to play with.

The following files are available from this page in 2 formats. The first is the .yag file in text format. You can copy the text from the page, paste it to a text reader like notepad, and save it as whatever.yag. Then move that file into your yagicad 4.1 program directory. You can also read the .yag file from here. The first info in the file is the title and description. The first number is the forward gain in db. The second number is the front-to-back ratio. The 3rd number is the actual impedance of the antenna. The 4th number is the reactance. The 5th number is the # of elements. The columns are: element length, distance from the end of the boom, and element diameter. All measurements are in meters.

Following the .yag file is the same file in a zip format that can be downloaded and unzipped directly into your .yag storage directory (may be ‘template’ if you’re running yagicad4.1 on WIN95/98/NT, or the main Yagicad4.1 working directory if you’re running it in DOS or Win3.x or lower).

chchg10.yag 10 element optimized yagi by Chen and Cheng. 13 db fwd with 11.59 f/b

chchg6e.yag 6 element optimized yagi by Chen and Cheng. 12.35 db fwd with 17.42 f/b

DL6WU20.yag 22 element long yagi by DL6WU. 15.98 db fwd with 21.66 f/b

foxant1.yag Simple 2 meter narrowband “sniffer” antenna. 7.45 db fwd with 47.33 f/b

foxant2.yag Simple 2 meter wideband “sniffer” antenna. 6.93 db fwd with 23.77 f/b

lawson3.yag One of Lawsons 3 element yagi designs. 7.45 db fwd with 47.33 f/b

lawson4.yag One of Lawsons 4 element yagi designs. 8.61 db fwd with 19.27 f/b

law4new.yag One of Lawsons newer 4 element yagi designs. 10.53 db fwd with 35.92 f/b

lawson5.yag One of Lawsons 5 element yagi designs. 10.17 db fwd with 27.99 f/b

lawson6.yag One of Lawsons 6 element yagi designs. 10.45 db fwd with 27.68 f/b

nbs3ele.yag A NBS 3 element yagi designs. 9.09 db fwd with 12.89 f/b

nbs5ele.yag A NBS 5 element yagi designs. 10.32 db fwd with 22.43 f/b

nbs6ele.yag A NBS 6 element yagi designs. 11.22 db fwd with 15.15 f/b

nbs12el.yag A NBS 12 element yagi designs. 13.09 db fwd with 17.99 f/b

nbs15el.yag A NBS 15 element yagi designs. 14.44 db fwd with 15.05 f/b

nbs17el.yag A NBS 17 element yagi designs. 14.18 db fwd with 18.10 f/b

iuy2m-6.yag A 6 element modified VK3DIP 2 meter yagi design by WB4IUY. Designed with a gap in the right place for the mast mount. 11.41 db fwd with 17.99 f/b

wb2hol3.yag A 3 element 2 meter ‘sniffer yagi design by WB2HOL for Fox hunting. Designed for easy transport during foxhunting, and a great front-to-back raito. 7.3 dbd fwd with > 50 dbf/b !! Visit WB2HOL’s Website for a full write up on this cool antenna!

22011el.yag This is an 11 element 220 yagi I (WB4IUY) designed for KG4D. It was designed around materials from an old 2 meter Cushcraft 11 element yagi.

432atv8.yag This is a 8 element ATV yagi for 432 mhz scaled from a 144 mhz Rutland yagi and optimized by KD2BD for ATV use. Constructed on a PVC boom. Very wide banded and excellant for 70 cm ATV use.

900-6el.yag This is a 6 element ATV yagi for 900 mhz that I (WB4IUY) designed on a 0.32m PVC boom. 10.47db fwd with 17.52db f/b.

900-10e.yag This is a 10 element ATV yagi for 900 mhz that I (WB4IUY) designed on a 1.05m PVC boom. 12.73db fwd with 11.44db f/b.

900-24e.yag This is a 24 element ATV yagi for 900 mhz that I (WB4IUY) designed on a 1.5m PVC boom. 14.55db fwd with 16.09db f/b.

900vhfc.yag This is a 24 element ATV yagi for 900 mhz designed by DL6WU on a 2.5m PVC boom. 15.54db fwd with 20.92db f/b.

Visit WB2HOL’s Website for a full write up on this cool DF antenna built from a metal Tape Measure! Optimized on YagiCad.

Visit VK3VT Fox hunt beam from an article by Lawson in Ham Radio Magazine.

Other antenna design programs can be found on the TEARA software page.