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Introduction
Welcome to this blog where we will be discussing End Fed Half Wave Antennas. This type of antenna has been a popular topic on this channel, and for good reason. It is a versatile and useful antenna, especially as we head into the winter months. In this blog, we will explore the concept of End Fed Half Wave Antennas, and provide some tips and tricks to make them more interesting and accessible for various scenarios.
Understanding the End Fed Half Wave Antenna
The End Fed Half Wave Antenna is a length of wire that is exactly half the wavelength of the lowest band it is intended to operate on. For example, on the 40-meter band, the wire would be approximately 66 or 67 feet in length. This wire is connected to a 49:1 transformer, which in turn is connected to your transceiver using a short length of coaxial cable. The great advantage of this antenna is that it eliminates the need for a long length of coaxial cable, making it more convenient and efficient.
Tips and Tricks
Converting to 80 Meters
If you want to use the End Fed Half Wave Antenna on the 80-meter band without increasing its length, you can use a loading coil. The loading coil is connected in series with the antenna and is placed at the end of the antenna. By adjusting the number of turns on the loading coil, it can act as a loading coil and a choke, isolating the 80-meter resonator section. This allows you to resonate the antenna specifically on the 80-meter band without affecting the other bands.
Shortening the Antenna Length
If the standard length of the End Fed Half Wave Antenna is too long for your needs, there are ways to shorten it for specific bands. For example, if you primarily operate on the 20-meter band, you can simply cut the antenna to a shorter length, such as 33 or 34 feet. Alternatively, you can use a loading coil at the center of the antenna to achieve a shorter length. By experimenting with the number of turns on the loading coil, you can find the optimal length for your desired band.
Adding a Tuned Trap
If you want to use the End Fed Half Wave Antenna on a band that is not a harmonic of the base band, such as 18 meters, you can use a tuned trap. The trap isolates the 18-meter half wave while allowing other frequencies to pass through. By adding a short length of wire, you can resonate the antenna on the desired band. This method allows you to utilize the End Fed Half Wave Antenna on bands that would not typically be possible using harmonic relationships.
Fitting the Antenna in a Small Garden
For those with limited space in their gardens, the End Fed Half Wave Antenna offers some interesting possibilities. One option is to use the inverted L configuration, where one antenna is fed at ground level, and the other is fed in the air. This configuration allows for a total antenna length of 40 feet. Additionally, by experimenting with different bending angles, you can further modify the radiation pattern and make the antenna more omni-directional.
Radiation Pattern and Additional Considerations
The radiation pattern of the End Fed Half Wave Antenna is very similar to that of a dipole. As you change bands, the antenna transforms from a half-wave dipole to a full wave or one and a half waves, depending on the band. It is important to note that bending the antenna can modify the radiation pattern, making it more omni-directional. It is also recommended to use a line isolator to ensure accurate SWR readings and to reduce RF interference.
Conclusion
The End Fed Half Wave Antenna is a versatile and efficient antenna that offers great performance in various scenarios. Whether you have a small garden or need a portable antenna, the End Fed Half Wave Antenna can be adapted to suit your needs. By utilizing the tips and tricks discussed in this blog, you can create your own End Fed Half Wave Antenna and enjoy the benefits of this reliable antenna design.
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