Many of my ham friends, who know that I have a good knowledge of antennas and propagation, have asked what is a good height, or the best height for a horizontal antenna.
To give an answer to this relevant question we need to get information on the desired use of the antenna, on what bands are to be used and the primary distances to be covered, short, medium or long range.
Many Hams are not interested in DX so short and medium range communications is all that is necessary, however ,most Hams would want to put up antennas that will do everything.
With these questions in mind I recommend reading a very informative article on this subject from the ARRL. It is titled Antenna Height and Communications Effectiveness and can be viewed and downloaded as a pdf file by going to:www.arrl.org/files/file/antplnr.pdf.
This article was written to help explain to government officials who control zoning and other local regulations that affect tower height, why amateur radio operators need substantial towers for their operations. The discussion on propagation and antenna heights in the article is fairly complete and informative.
Another authoritative work which includes the subject of antenna height above ground is Yagi Antenna Design by Dr James L. Lawson. This is an ARRL publication and echoes the conclusions of the article cited above.
In a nutshell, the best overall antenna height for the bands 20 through 10 meters, is around 1.5 wavelengths.
In a nutshell, the best overall antenna height for the bands 20 through 10 meters, is around 1.5 wavelengths. At this height, the performance of a Yagi antenna is not seriously degraded from a free space design and the antenna provides good gain at the critical takeoff angles from 3 to 17 degrees. The 1.5 wavelength height would be 105 ft on 20 meters, 82 ft on 17 meters, 70 ft on 15 meters, 60 ft on 12 meters and 53 ft on 10 meters. A very good compromise for a multiband antenna such as a tribander, a StepIR or a log periodic is 70 ft. Many Hams have reported that they have observed drastic performance improvements, particularly on 20 meters, by going from say 40 ft to 70 ft.
I have firsthand experience with an antenna that is too high for general operation. A few years back I had a wide spaced 4 element Yagi mounted at the top of my 180 foot tower (see photo above). Since I am on top of a hill with the land sloping down at least 100 ft in all directions, the effective height of the antenna was 230 ft, which is 3 ½ wavelengths. This antenna was a high-performance band opener. Comparing signals with other stations in the area with lower antennas, when the band was first opening up or when conditions caused the signals to arrive at very low angles I could hear distant stations, such as signals coming from Antarctica, as strong as S5 to S6, when the other stations in the area could not detect anything on the frequency.
As the band opened up and the signals began arriving at higher angles, the advantage disappeared and actually reversed on many signals. Some stations in North America would be 20 over S9 at other stations in the area with lower antennas and be S9 at my station. In addition, many times signals from Europe would suffer in the same way.
However, on the lower bands, 40, 60, 80 and 160 meters the best height is more dependent on the amount of distance you want to cover. Many times on these bands, strong signals will arrive at near vertical angles. If you wish to maintain communications over short ranges, 30 to 200 miles, your antenna should have a good response at radiation angles from 30 to 90 degrees. Because of their
size, most Hams cannot put up directional antennas for these bands, they use wire dipoles. A majority of Hams have their dipoles at 40 ft height or below. At these heights, on the 4 lower bands most of the RF energy that is radiated is radiated upward between 30 and 90 degrees. These antennas work well when communicating with other stations in North America, however, it requires the infrequent
enhanced band conditions that allow DX stations to come in at high angles for these low antennas to allow communications with very distant stations (over 2000 miles).
If you want to work DX on the 4 lower bands with a horizontal antenna, then good heights would be 150 ft on 80 meters, 110 ft on 60 meters and 80 ft on 40 meters. Good low angle heights for 160 meters is impractical for 160 meters, which would need 300 ft.
As a good low angle radiator alternative to the horizontal antenna, you should consider putting up a properly installed vertical. The vertical antenna is a future subject.
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