VE7BQH Antenna Comparison Tables

Over the last quarter century, antenna performance has improved dramatically. Thanks to the development of computer modeling software, antennas can now be designed  to provide excellent results. Many older antennas are still in use around the world that were built using less sophisticated techniques. A number of 6m  operators have  wondered if it is time to upgrade their antenna systems, especially in view of the poor solar cycle and increased number of worldwide EME contacts being made by smaller stations.

CAUTION NOTES ON ANTENNA GAIN:  Many antenna manufacturers claim high gain values for their antennas (this is especially true for HF antennas) by including extra ground gain from an installation over some ideal ground plane (which very seldom is found by hams living in the real world).  Others choose to boost their gain figures over 2 dB in their advertising literature by listing the gain as compared to a theoretical isotropic radiator in free space (dBi).  This makes comparison of various specifications from different sources very difficult.  Howeer, the comparisons in these tables are all based on comparing apples to apples.  Lionel has spent a great deal of effort creating very valuable and unique comparison tables showing FREE SPACE antenna performance in terms of dBD gain.   This means, how the antennas will work if aimed up in the sky, compared to a DIPOLE antenna without any ground effects.  How an antenna will actually perform for you, depends to a very large extent on your location.  When a yagi is aimed at the horizon, the results between users of the same antennas can be quite different!  This is partially due to interaction with other antennas and feedline losses, but it also varies depending on the terrain in front of the antenna, height of the antenna above the ground (in terms of wavelengths), and whether there are obstacles in front of the antenna (such as houses, cars, other buildings, hills, mountains, etc.) or underneath it (such as large HF yagis, a rooftop, etc.) to prevent valuable ground gain reflections from reaching the antenna and increasing the effective gain of the antenna.  Gain created from the additive effects of signal reflections from the ground is called Ground Gain, and can result in much higher (up to 6 dB) effective antenna gain in antenna lobes at specific elevations!  That means a single antenna in an ideal installation with perfect ground gain can perform like 4 four antennas - at certain incoming signal elevations, anyway.  The gain of these ground gain antenna lobes (and the nulls in between them) depend somewhat on antenna height and the elevation of the lobes depends on the gain of the antenna, the height of the antenna and the flatness of the terrain in front of the antenna.  ON4KHG has written extensively on ground gain (a comprehensive article first appeared in DUBUS magazine in March, 2011) and prepared tools to help individual operators determine if and where the ground gain lobes may be for their own antenna installations.  Typically, the best way to "map out" your own ground gain lobes is to monitor moon echoes (either yours or the signal from someone else) during your moonrise and/or moonset.  Of course, that only provides data for antenna performance in those particular directions, but it is a very useful indicator of what can be expected.  In fact, this extra ground gain is what makes it possible for single yagi VHF stations to complete worldwide EME contacts - they complete the contacts when the rising or setting moon passes through one or more of their antenna's ground gain lobes.  An example of how height affects the elevation and number of ground gain lobes of a high gain 6m yagi is shown HERE.

There is no question that each operator has different interests and constraints. Some want to arrange various antennas to "fill in the nulls" in ground gain patterns so they  can be assured of not missing F2 signals coming in at certain angles. Others want to increase maximum signal strengths while still fitting the antenna into their gardens. And  still others are interested in assembling an antenna system that will have enough free space gain to enable them to complete EME contacts while the antenna is elevated  (without any ground gain). With the differences in how antennas are marketed and what specifications are published, it is no wonder that many hams have expressed confusion when they try to compare antennas to determine what would be the best choice for their particular situations.

Lionel Edwards, VE7BQH, is well known for his pioneering work in EME and his knowledge of antenna design. His comparison table of 2m antenna designs has been a  valuable resource for weak signal enthusiasts on that band. The recent increase in larger antennas for this band, along with the growth of interest in 6m EME, has resulted in many requests for such a 6m antenna comparison table, too.  Lionel now has generously put together a table comparing a number of popular 6m antennas to help guide  Magic Band operators on antenna decisions. This table was painstakingly prepared to include the free space gain of each yagi with respect to a dipole, the optimum  and 75% of optimum stacking distances for both two and four yagis and resulting gain figures, and the SWR of a single antenna 150 kHz from the design frequency. The SWR value provides an indicator of the "Q" of the antenna, and how likely it is to be affected by rain, ice and snow; the narrower the bandwidth of the antenna, the more susceptible it is to such de-tuning by the weather. Please join with me in thanking Lionel for graciously agreeing to undertake the very laborious challenge of preparing  these tables.

DOWNLOAD ALL VE7BQH 70CM, 2M, 6M COMPARISON TABLES TOGETHER IN EXCEL FORMAT

The purpose of the above tables is to provide comparison information for 6m operators selecting antennas, and stacking information for experienced weak signal operators interested in constructing antenna arrays to maximize gain.  VE7BQH does not have the time or interest to design custom antennas for individuals.  That is why I have provided some links below to more information about some of the antennas included in the comparison table.  For many people, the best value is to purchase a commercial antenna already constructed with hard-to-find materials.

If you are interested in constructing your own custom antenna from scratch, there are many excellent articles on the internet, along with sources of materials convenient for you.  For example, Texas Towers provides telescoping tubing for antenna projects, your local hardware store provides HDPE kitchen cutting boards (for insulated mounting plates, as required in all the YU7EF designs), and McMaster-Carr provides all sorts of bolts and fasteners of different type materials.  If you are looking for materials to build a split dipole driven element, simply pick up some nylon, fiberglass or HDPE at your local hardware store or plastics distributor and insert into the two halves of the dipole on an insulated mounting block.  If you don't have a local hardware store or plastics distributor, you can mail order many sizes of insulating rod materials from McMaster-Carr or Small Parts. You can certainly find more examples of suppliers and photographs of what others have done by simple searches on the internet.  Just remember that any metal plates for attaching the elements, or changes in the diameter of the elements, will require that the element lengths be modified correctly.  If you do not have the experience and references on how to do this, you should not strike off on your own -  If you are duplicating any high performance antenna you should exactly follow the instructions provided by the designer.