VIDEO
Are you facing limitations on what antennas you can erect? Perhaps your neighbours have a say in your amateur radio pursuits? If so, I have a solution for you: the pop-up dipole antenna! Let's dive into the details of this ingenious design, crafted from easily accessible materials, and how it can elevate your ham radio experience.
The Inspiration Behind the Antenna
It all started during a casual visit to my local coffee shop, where I often find inspiration for new projects. While sipping my coffee, I began to think about antennas that are both efficient and unobtrusive. This led me to experiment with Ampro antennas, specifically a helically wound model that could serve as a compact solution for amateur radio enthusiasts.
Understanding the Ampro Antenna
The Ampro antennas feature a helical winding at the base, transitioning into a whip halfway up. This design allows for easy adjustment of the whip to achieve resonance. The antenna I focused on is designed for the 20-meter band, and I've been testing its efficiency. My previous videos showcased its performance as a base vertical antenna, which turned out to be surprisingly effective.
- Performance Insights - When I mounted the Ampro antenna just a metre above the ground, using a single radial, I was amazed by the results. Despite being half the size of a full-sized vertical, it performed exceptionally well, yielding contacts comparable to my traditional dipole. The vertical polarization of the Ampro does present some differences when compared to horizontally polarized dipoles, but overall, it proved to be a reliable choice.
Testing It as a Dipole
With my positive experiences using the Ampro as a vertical, I decided to push the boundaries and test it as a dipole. I must admit, I was initially sceptical about using two mobile whips for this purpose. I worried about the feed impedance being too low and the overall functionality. However, the only way to truly know was to put it to the test.
- Setting Up the Dipole - To create a dipole, I needed a bracket to mount the two mobile antennas. Luckily, we offer a suitable bracket that accommodates antennas with a 3/8-inch thread. One end connects to the inner conductor of the coaxial cable, while the other connects to the earthy side, requiring no insulation. This setup provides a solid foundation for a dipole configuration.
I've also been using a telescopic mast to elevate the antenna. These fiberglass masts are incredibly sturdy and allow for easy height adjustments. The locking mechanism enables you to secure the antenna at various heights, making it versatile for different situations.
Adjustments and Tuning
As I set up the dipole, I encountered a challenge: the whip telescopes inside the helical section, which can affect the antenna's Q factor. I discovered that when the whip is inserted too deeply, it can lower the antenna's frequency and introduce losses. To mitigate this, I trimmed 8mm off the whip, which improved the SWR readings significantly.
- Measuring SWR - Using an antenna analyzer, I observed the SWR readings at resonance, which were quite promising. However, if you push the elements in too far, expect to see a poor dip on the SWR meter. It's essential to make adjustments gradually, trimming a little at a time until you achieve the desired results.
Real-World Testing
After tuning the antenna, I was eager to test its real-world performance. I made several QSOs, even while the antenna was only about 15 feet above ground. The results were impressive, and I quickly established contacts with operators from various locations.
- Contact Experiences - During one of my tests, I received a 59 report from a station in Italy. The audio quality was clear, and I was pleasantly surprised by the antenna's effectiveness at this height. Although I found it about an S-point down compared to my full-sized dipole, the pop-up nature of this antenna makes it a fantastic option for limited spaces.
Directivity and Benefits
While the pop-up dipole is not highly directional, it does have some directivity, providing around 6 to 8 dB gain when rotated. This makes it a practical choice for both local and distant communications. The ability to telescope it down when not in use is another significant advantage, as it keeps the antenna discreet and avoids any neighbour complaints.
Conclusion
If you're considering an antenna that combines portability, efficiency, and ease of setup, the pop-up dipole is worth exploring. It’s a compact solution that can fit into tight spaces while still delivering solid performance. I encourage you to give it a try and see how it works for you. Links to the components I used are provided below, and I hope this inspires you to elevate your ham radio experience.
Thank you for joining me on this journey into the world of pop-up dipole antennas. Until next time, happy hamming!
For more information please visit our online store or alternatively contact us and our team will be happy to assist you