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Introduction
When it comes to trying out antennas, having open space is essential. That's why I often come down to this park where we have our holiday home. In today's blog, I want to talk about an alternative to the 9:1 unun that I've been experimenting with recently. But before we dive into that, let me share my experience with the 9:1 unun.
My Experience with the 9:1 Unun
Over the past few years, I have tried using the 9:1 unun on and off, but I have never been truly satisfied with its performance. While many hams swear by it, I found that it didn't live up to my expectations. The 9:1 unun is essentially an RF transformer with a 9:1 ratio. The idea is that it can transform a 450 ohm impedance to 50 ohms, which is ideal for transceivers. However, in practice, it often falls short.
One of the main issues with the 9:1 unun is that it is designed for non-resonant antennas. These are antennas that are neither a half wave nor a quarter wave or multiples thereof on a particular frequency. While theoretically, the 9:1 unun should work well with non-resonant antennas, it often fails to deliver the desired results, especially with shorter lengths of wire.
Commercial designs for the 9:1 unun typically recommend lengths of wire around 70-90 ft for optimal performance. However, for my own portable work, I prefer using a shorter length of wire. This might explain why the 9:1 unun didn't work well for me.
An Alternative: The Floating ATU
In my quest for a better alternative, I came across the concept of the floating ATU. This antenna tuning unit offers more flexibility and better performance compared to the 9:1 unun, especially for portable operations. Let me explain how it works.
The floating ATU is essentially a combination of two antenna designs: the W3 EDP antenna and the T2LT antenna. The W3 EDP antenna is an 84 ft wire antenna fed with an antenna matching unit (ATU). The T2LT antenna, on the other hand, is a single-band antenna that uses a quarter wave of wire and a quarter wavelength of coaxial cable to form a half-wave dipole.
By combining these two designs, we can create a flexible antenna system that works on multiple bands. The main radiator is a long length of wire, the LDG ATU acts as the matching unit, and the counterpoise is formed by choking off the coaxial cable. The beauty of this setup is that the ATU provides great flexibility, allowing you to tune the antenna for optimal performance on different bands.
Setting Up the Floating ATU
Setting up the floating ATU is relatively simple. You will need an LDG Z-100 antenna tuning unit, which benefits from an internal battery supply. The Z-100 is a versatile tuner that can run off internal AA cells, making it ideal for portable operations.
To connect the Z-100 to your transceiver, you will need a 3.5mm stereo lead. The Icom IC-705, for example, has an ATU interface with a 3.5mm stereo socket. Simply connect one end of the lead to the Z-100 and the other end to the IC-705, and you're good to go. The tuning process is automatic and takes just a few seconds.
For the main radiator, you can use a length of wire that suits your needs. While the W3 EDP antenna recommends 84 ft, you can adjust the length based on the bands you want to operate on. The measurements are not directly proportional to the W3 EDP antenna, but as long as you maintain the relationship between the different elements, you should achieve good results.
Benefits of the Floating ATU
The floating ATU offers several benefits over the 9:1 unun. First and foremost, it provides greater flexibility in terms of band coverage. While the 9:1 unun may require additional antenna tuning units to achieve a decent match on different bands, the floating ATU can handle multiple bands without the need for additional equipment.
Additionally, the floating ATU is more efficient and reliable. The use of an ATU ensures that the antenna is properly matched, resulting in lower losses and better performance. With the 9:1 unun, a significant mismatch can lead to heating of the ferrite core, which can further degrade the performance.
Another advantage of the floating ATU is its versatility for portable operations. The LDG Z-100 tuner runs off internal batteries, eliminating the need for an external power supply. This makes it ideal for field operations where power sources may be limited.
Conclusion
While the 9:1 unun has its merits, the floating ATU offers a better alternative for those looking for improved performance and flexibility. By combining the concepts of the W3 EDP antenna and the T2LT antenna, the floating ATU provides a versatile and efficient antenna system that can be easily tuned for optimal performance on different bands.
Whether you're a seasoned ham operator or just getting started, the floating ATU is worth considering for your portable operations. Its ease of use, flexibility, and reliability make it a valuable tool in the world of amateur radio.
To learn more about the floating ATU and other ham radio products, visit our website or give us a call. We have a wide range of products in stock and are always happy to assist you with any questions or concerns.
Thank you for your support, and happy ham radio!