A 17M Dipole Antenna
I have sometimes heard dipole antennas referred to as "the simplest type of antenna that works well." They certainly are simple to make, and they do have certain advantages. A full size resonant dipole needs nothing else to make it work. You still have to consider ground losses and reflections, but they don't affect operation to the same extent as with a ground mounted quarter wave vertical, where the ground supplies the "missing half" of the antenna. Dipoles have some directivity and therefore, some degree of noise rejection, which is helpful especially for weak signal reception. They do have a null off the ends, but it's pretty narrow. Ideally, you would like to be able to rotate the dipole to obtain maximum signal from the distant station and avoid having them in a null, but it's not usually a problem if you can't.
For this experiment, I configured my dipole broadside to the NE and SW. This covers a lot of useful areas, including Europe and Australia. Closer in, it covers most of the NE part of the United States along with the Southwest. I was able to re-use the wire and balun from the 17M Delta Loop and I mounted my dipole about 26 feet high, running from a tree to a TV tower on the roof. This is about 1/2 wavelength above ground, which is a good height for avoiding ground losses and obtaining good lower angle radiation for working DX.
Right away I noticed lower noise levels compared to the vertical. My noise level typically ran S1 to S2 on the dipole and S3 to S4 on the vertical. I had my station configured such that I could switch immediately between the two antennas, which is how I like to make comparisons. For the first time I found that I could hear (and work) DX stations in Europe. Some of the signals that were an honest S9 on the dipole were barely readable on the vertical, especially with its higher ambient noise level. Signals from Arizona and California were sometimes equal on the two antennas, but mostly a bit stronger on the dipole. During fades, it was possible at times to observe stronger signals on the vertical, but usually not for long.
In the end, I decided that because most 17M stations were stronger on the dipole most of the time, I no longer needed the vertical, so I took it down. I replaced that antenna with a two-band vertical for 40 and 80 meters. More about that one in another post. Anyway, the dipole worked well, especially considering its modest size and low cost, and I decided that it's a keeper. I am using a Guanella type balun and feeding it with about a 50' run of good quality RG-8X coax. It easily handles 600 watts from my amplifier and the SWR is under 1.4:1 across the relatively small 17M band. I don't use any additional matching devices in the feed line.
For this experiment, I configured my dipole broadside to the NE and SW. This covers a lot of useful areas, including Europe and Australia. Closer in, it covers most of the NE part of the United States along with the Southwest. I was able to re-use the wire and balun from the 17M Delta Loop and I mounted my dipole about 26 feet high, running from a tree to a TV tower on the roof. This is about 1/2 wavelength above ground, which is a good height for avoiding ground losses and obtaining good lower angle radiation for working DX.
Right away I noticed lower noise levels compared to the vertical. My noise level typically ran S1 to S2 on the dipole and S3 to S4 on the vertical. I had my station configured such that I could switch immediately between the two antennas, which is how I like to make comparisons. For the first time I found that I could hear (and work) DX stations in Europe. Some of the signals that were an honest S9 on the dipole were barely readable on the vertical, especially with its higher ambient noise level. Signals from Arizona and California were sometimes equal on the two antennas, but mostly a bit stronger on the dipole. During fades, it was possible at times to observe stronger signals on the vertical, but usually not for long.
In the end, I decided that because most 17M stations were stronger on the dipole most of the time, I no longer needed the vertical, so I took it down. I replaced that antenna with a two-band vertical for 40 and 80 meters. More about that one in another post. Anyway, the dipole worked well, especially considering its modest size and low cost, and I decided that it's a keeper. I am using a Guanella type balun and feeding it with about a 50' run of good quality RG-8X coax. It easily handles 600 watts from my amplifier and the SWR is under 1.4:1 across the relatively small 17M band. I don't use any additional matching devices in the feed line.