In the previous Winter I built a HB9CV-in-a-box for 23cm for my uplink to the local ATV repeater PI6ATV. Although this antenna works nicely, its gain just isn’t enough when their 23cm preamp is broken (which, unfortunately, is the case most of the time). To achieve a more steady uplink, I decided to build an antenna with a bit more gain, at least 6 dB extra compared to the HB9CV. A short yagi should make this possible.

Design criteria

There are lots of designs available for yagi antennas. Guenter Hoch DL6WU has researched this subject for decades, nowadays his design formulae are accepted throughout the world in both commercial and home made antennas. Many other designs are actually just small modifications of the DL6WU formulae. In the past I built a couple of 2m beams using DL6WU’s design, so I decided to use this again, now for my 23cm yagi. I started with my design criteria:

Yagi Design Programs

• Center frequency: 1260 MHz
• Bandwidth (3 dB): 1240-1280 MHz
• Gain: 10 dBd or more
• Polarization: horizontal
• Mount: in front of mast
• Lightweight

Construction

Because of low weight and easy handling I mostly use aluminium to construct VHF/UHF antennas. This material is also easy to drill, saw and grind. You can buy it in most DIY shops. For this antenna I bought an square bar (15x15mm), made of aluminium, length 1 meter. At one end I mounted a standard available mast mount, leaving about 90cm for the actual antenna. Using the DL6WU formulae, this results in a 14 element yagi, with a gain of over 13 dBd. I used the DL6WU spreadsheet calculator of DF2CK to calculate all measurements. Unfortunately DF2CK’s website has vanished. Luckely I kept a local copy of the sheet to calculate your own yagi, click here to download the sheet. I used AlMg3 welding rods for the radials. These rods have a diameter of 4 mm. The dipole is made of 6 mm2 copper wire, matched with a matching loop (1/2 wavelength coax or semi-rigid) and mounted to a female N connector.

• This is an Excel spreadsheet template to design DL6WU Yagi antennas based on the following references by Guenter Hoch, DL6WU. The program dl6wu-gg.bas.
• Yagi Calculator is a Windows program that also runs well on Linux, Ubuntu 8.10 under Wine, 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. Category: Personal and Home. Developer: John Drew - Download.

Yagi Calculator (Yagi.exe). Yagi Calculator is a Windows program that also runs well on Linux, Ubuntu 8.10 under Wine, to produce dimensions for a DL6WU style long Yagi antenna. Yagicad is a fully integrated analysis and design package primarily intended for VHF yagi aerials. With Yagicad it is possible to enter a base design from scratch or use one of a number of saved well known designs. This design can then be optimised or scaled to suit particular requirements.

These are my inputs for the spreadsheet:

• Frequency MHz: 1260
• Boom diameter cm.: 1.5
• Element diameter mm.: 4
• Element Thru Boom (“Y/N”): Y
• Boom Length (Metres): 0.89

This spreadsheet returned these specifications, the real specifications will differ a bit, but it will give you an idea what to expect:

• Gain: 13.6 dBd
• Usable bandwidth: 1234.8 to 1285.2 MHz

And it returned these element sizes:

The finished antenna looks very good, but I have to admit that the driver is a bit wacky. Any hints to improve this are welcome.

Results

The ATV repeater now receives a decent signal, resulting in a steady and colourful picture. Unfortunately I don’t have equipment to measure the impedance and resonance point of my antenna. Whenever I’m able to measure this, I will update this article.

Reproductions

Lex PH2LB managed to reproduce this antenna to examine whether it’s possible to make contacts at the 23cm band from his home. He send me some pictures:

If you’ve built your version of this antenna, please let me know your experiences, and send me some pictures of it!

This article was also published in:

Ever since I started working on 144MHz, back in 1985, my major problem was fighting with a city noise (man made noise) since I live in a medium sized city but with a lot of industrial facilities. Sometimes noise was just unbearable in some particular directions and it was almost impossible to listen for a weak signals. At that time I was using very popular and well known DL6WU 11 element yagi – very good performance antenna but obviously still not good enough – now I see and know why. Most of my activity those days was high speed CW MS and all of you that have done that kind of communication know that very often reflections were weak, particularly when we operated out of major meteor showers, trying to use sporadic meteors.

Later I have built a new 15 element DL6WU antenna that gave me better results noise vise and more gain but it was not that efficient in collecting signals reflected from meteors due to narrow beam width.

As soon I got my first PC in 1991 (286/12MHz with math coprocessor and 5MB RAM) I came across “Mininec 1” software for antenna simulations and started “playing” with it. It was very useful to visualize antenna patterns and excitation parameters. However, due to very slow computer it was painful to do it - just for one calculation I had to wait for 15 to 20 minutes to end. Very quickly I got W7EL program “Elnec 1.0” that was much more user friendly so I was spending more and more time analyzing various antennas and trying to do some modifications to existing ones. As a result, I came to somehow modified design of 4 WL DL6WU antenna and have built it immediately to see if that really works. To make it short, it was noticeably better than original antenna and that gave me first ideas of where design has to go to reduce city noise pickup. With those two antennas stacked vertically I even worked quite some number of EME stations in early 90’s, only in CW, using only my TR-9000 and about 500w power amplifier.

Later, with AO software that was even better, having optimization feature available, actually I started designing my own antennas, rather than just doing modifications to published designs. Once I got NEC2 program things were much better and results were more reliable and I am using it ever since. There are many different programs at the market today but most of them are giving similar results and the difference is just how the authors have developed user interface and couple of different options. For several years now I am using 4nec2 software from Arie Voors, in my opinion currently the best software available.

Being intrigued with antenna performance I have spent many hours analyzing any antenna I came across in various magazines and publications, just to verify declared specifications and see if they are really that good as they say. Well, I must say that probably > 70% of those antennas were not even close to declared specifications and were all but good and just a few actually confirmed declared specifications. Doing those analyses I also realized how many mistakes were made and some statements were false, no wonder good antennas were rare those days. Having all that in mind, ever since then, I never used any other antennas but my own designs.

Naturally, it took me many years and thousands of hours on simulations and optimizations until I came to designs that are compatible to some of most famous designs. For a long time I was actually walking in the dark, not being able to make a brake through how to get rid of those side lobes since I did realize they are to blame for increased local, man made noise pickup.

Thanks to Peter Sundberg program Yagi Analysis 3.54 I finally had an opportunity to actually “see” where the problem really is, since it is obviously showing what part of radiation pattern is to blame for good or poor noise specification of the antenna. Only with that program I could see that total antenna temperature is mostly dependant on suppression of side lobes and clear pattern. At the same time, it was obvious that F/B ratio is not so important since difference from say 20dB to a 25dB would reduce total temperature only few °K which is not worth too much sacrifice. Many designs might have been much better if only people doing them were not so much focused on F/B ratio that, on the other hand, led to poor side lobe suppression.

As every optimization is a “game” with various trade off parameters, I was focused on getting design with pure 50 Ohm impedance, reasonably wide operating range, gain as close to FOM as per DL6WU formula and suppressed side lobes to acceptable level in order to get as good G/T ratio as possible.

Most of those designs were tested by myself or my friends and results were very good. However, for a very long time I did not publish my designs for various reasons. Finally, after several friends told me I should do it, I have sent files to Lionel VE7BQH for his review and opinion. After they were published in his chart, many people started asking questions and information and I decided to publish them on the WEB as I was not able to answer numerous mails I was receiving on daily basis.

However, I am confident that each and every of these antennas can be improved even more, so I will continue working on them and hopefully will come up with even better results so there is definitely more to follow.

*****************************************************************************

When I started this article I was thinking what antenna should I present and it didn’t look reasonable to pickup one of the antennas already published on the WEB. Instead, I have decided to be an antenna that was especially developed for those living in extremely noisy areas such as big cities or huge industrial facilities who are suffering the most from man made noise.

Dl6wu Yagi Calculator

As I said before, I was always fighting with heavy city noise and was always trying to figure out way to reduce it as much as possible. In order to get antenna with maximum suppression of side lobes it is necessary to give up much more gain than usual. Idea is based on my consideration like this:

Yagi Design Online

If my antenna has to pick up noise from all directions, and it does, let me than reduce pick up from all other directions but from main lobe. I will give up some more gain than usual for superior side lobe suppression but incoming signals will be heard with less birdies and other junk.

As a result, antenna that will be presented here is something that can not be considered as a top class antenna by looking to gain or G/T ratio. As a matter of fact, if someone will compare gain of this antenna with some other designs of the same boom length, it is about 0.5-0.6dB below the DL6WU F.O.M. (figure of merit) for that boom length. I am considering it worth doing and acceptable if I can reduce city noise pick up.

This boom length is chosen as, from my experience, such antenna has optimal -3dB beam width for MS and terrestrial communications. Two of those vertically stacked antennas will give us more than sufficient gain for successful work on daily basis and H stack of four antennas should be sufficient even for EME .

Vhf Yagi Calculator

Since there are so many different ways of antenna construction and element mounting I am always giving free space dimensions for elements – letting everyone to execute building preferred way. Naturally, depending on the chosen construction technique, appropriate boom correction to the element lengths has to be applied in order to maintain original specifications.