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Exploring the ATAS-25: A Versatile Portable Antenna Solution
The world of portable ham radio operations often requires antennas that are efficient, easy to tune, and simple to set up. The ATAS-25 antenna, designed for portable use, covers frequencies from 40m to 70cm and handles up to 100 watts. In this blog post, we will explore various innovative ways to utilize the ATAS-25, including its potential for mounting on a vehicle roof. This approach not only enhances efficiency but also opens up new possibilities for portable operations.
Getting Started with the ATAS-25
The ATAS-25 antenna stands just over 2 meters tall, making it a bit longer than its mobile counterpart, the ATS-120. This increased height can lead to better efficiency, particularly when used for portable operations. Designed to fit onto a standard camera tripod, the ATAS-25 is perfect for outdoor setups. In previous tests, it has shown impressive performance, making it a reliable choice for ham radio enthusiasts.
Why Consider Vehicle Mounting?
One interesting possibility is to mount the ATAS-25 on the roof of a vehicle. While this setup isn’t suitable for mobile operations, it can significantly improve performance. Mounting the antenna on a car roof allows the vehicle to become part of the antenna system. The car acts as a ground plane, enhancing radiation efficiency. Essentially, the car body can function similarly to a vertical dipole, with the antenna as one half and the vehicle as the other.
Setting Up the ATAS-25 on a Vehicle
To experiment with this setup, the first step involves placing the ATAS-25 on the roof of a van. The coax feed connects to the bottom of the antenna, with a ferrite core acting as a line isolator. This setup prevents the coax from interfering with antenna operation. Next, three radials, each about 3 meters long, are spread out on the roof of the van to create an effective ground plane.
Initial Setup Steps
- Attach the coax feed to the ATAS-25.
- Use a ferrite core as a line isolator.
- Spread the three radials across the roof of the van.
While it may be challenging to spread the radials evenly without a step ladder, simply throwing them onto the roof can suffice for this experiment. The key is to ensure that the radials can interact with the vehicle’s metal surface, forming an effective ground plane for the antenna.
Testing Performance and Resonance
Once the antenna is set up, the next step is to check the resonance on different bands. The initial test for 20m showed excellent SWR(Standing Wave Ratio), indicating that the radials and the metal roof were functioning effectively together.
Results Across Frequency Bands
- 20m Band: Excellent SWR, confirming resonance.
- 15m Band: Also showed excellent performance.
- 40m Band: Achieved a remarkable SWR of around 1.2:1.
- 10m Band: Similar low SWR results.
- 6m Band: Required the removal of two sections to resonate.
This versatile performance highlights the potential of using the ATAS-25 mounted on a vehicle, making it a practical option for portable ham radio operations.
Experimenting with Different Vehicles
To further explore the ATAS-25's capabilities, the next test involved using a family car instead of the larger van. The setup was similar, but adjustments were made to ensure compatibility with the smaller vehicle. A large solder tag was attached to the antenna's base, allowing radials to connect securely.
Key Adjustments for Smaller Vehicles
- Use a larger solder tag to connect radials effectively.
- Ensure that the radials can still couple with the vehicle's metal roof.
After setting up the antenna on the family car, tests revealed that the performance remained strong, demonstrating that this method can be applied to various vehicles.
Surprising Results with Random Radial Placement
In a moment of curiosity, the radials were simply tossed onto the roof of the vehicle without any specific arrangement. Surprisingly, the performance remained consistent with the earlier tests, showing that even a casual placement can yield good results. This flexibility emphasizes the ease of use and adaptability of the ATAS-25 antenna.
Comparing Radial Effectiveness
Further experimentation involved running a 20m quarter-wave antenna from the ATAS-25 on the roof. The results were comparable to using the radials, indicating that the radials effectively couple with the vehicle's roof, much like a magnetic mount would.
Conclusion: The Versatility of the ATAS-25
The ATAS-25 has proven to be a highly versatile antenna, capable of delivering excellent performance for portable operations. Whether set up on a tripod in a field or mounted on a vehicle roof, it offers flexibility and efficiency.
As we head into the winter months, this antenna provides an exciting option for portable ham radio enthusiasts. The ability to quickly set up a station without obstructing foot traffic makes it an excellent choice for public spaces.
In summary, the ATAS-25 stands out as an effective solution for those seeking to enhance their portable operations. With its adaptability and ease of use, it truly is a fantastic addition to any ham radio setup.
Thank you for joining me on this exploration of the ATAS-25. I hope these insights inspire you to try new setups and get the most out of your portable ham radio operations. Until next time, happy radioing!