VIDEO
Messing about with antennas can be a rollercoaster of emotions. You might feel encouraged, disappointed, or even surprised. Over the last week, I experienced all three while experimenting with different antenna setups. Let me share my latest venture into the world of the Ampro antennas, particularly focusing on the vertical half wave dipole.
Getting Started with Ampro Antennas
My journey began with testing the Ampro vertical antenna for the 20m band. This antenna is just 2.25 meters tall, making it an ideal choice for those with limited garden space. I set it up about half a meter off the ground with a single radial and was pleasantly surprised by its performance. It handled 100 watts effortlessly and even managed 200 watts. There’s a larger version that can handle up to 600-700 watts, which adds to its versatility.
Next, I tried using the Ampro antenna in a mobile setup. Again, it performed admirably, but I learned a few essential adjustments needed for optimal use. If you're considering mounting the Ampro on your vehicle, be sure to check my detailed video for tips on adjustments.
Surprising Performance of Mini Dipoles
In another experiment, I opted for a mini dipole. To my astonishment, it worked incredibly well. I had good contacts, and it was only about an S point down compared to my full-size dipole. This was an unexpected success, reinforcing my belief in the potential of smaller antennas.
- Creating a Vertical Half Wave Dipole
- Design Configuration - Here’s the basic idea: I used a mobile whip for the lower part, which has a helical winding tuned to 20m, functioning as a quarter wave. By adding a full-size quarter wave, which is about 7 ft long, I effectively created a half wave dipole. The total height of the antenna is significantly shorter than a full-size dipole, making it more manageable for various settings. To feed the antenna, I set up a 49:1 unun at the base, allowing me to connect the coax cable directly. This configuration not only reduces the physical height but also simplifies the installation process. The antenna measures around 23 feet tall, which is much more achievable for many operators.
- Testing the Antenna
- Noise Levels and Performance
- Durability and Power Handling
Feeling inspired, I decided to take a step further and create a vertical half wave dipole using the Ampro antenna. Feeding a half wave dipole vertically can be tricky, as it typically requires feeding from the middle and routing the cable at right angles. I wanted to simplify this process. Hence, I aimed to feed it as an end-fed half wave dipole at the base, which should allow for easier feeding and effective performance.
After assembling the antenna, I connected it to my analyzer. The results were promising, showing a VSWR of 1.5:1, which indicates a broad response. The antenna was resonant just outside the bottom of the 20m band, which is typical when using a 49:1 unun, as it introduces a slight load that requires shortening the antenna.
I also conducted some listening tests, comparing the vertical dipole to my horizontal dipole. I noticed that the S meter readings were quite similar, indicating that the vertical was performing well. However, the real test came when I switched to a quieter part of the band.
Upon switching, I observed a significant increase in noise levels when using the vertical antenna compared to the dipole. The vertical picked up noise much more easily, which is a known characteristic of vertical antennas. In my case, being only 3-4 meters away from my house likely exacerbated this issue. Local noise can significantly impact the performance of vertical antennas.
If you're considering a vertical setup, I recommend testing the noise levels in your environment before committing. If the noise is manageable, the vertical can be a great option, especially since it allows for a shorter height requirement.
During my tests, I pushed the antenna to around 300 watts without any issues. It held up well under the load, and I had no concerns about overheating. This was encouraging to see, as many operators worry about their antennas' durability at higher power levels.
Overall, the antenna performed almost as well as a full-size vertical half wave. It’s particularly well-suited for DX operations due to its low-angle radiation pattern. I conducted a comparison with my half-size 5RB, and the results were strikingly similar.
Final Thoughts
While I was pleased with the performance, I couldn't ignore the noise issue. My horizontal dipole remained significantly quieter, with no noise at all when the preamp was off. The vertical, however, picked up a couple of S points of noise, making weak signals harder to discern.
As a result, I recommend ensuring that your vertical antenna is placed away from any noise sources. If you can get it further down the garden, the results may improve significantly.
Conclusion
The vertical half wave dipole is a fantastic option for those with space constraints. With a total height of around 23-24 ft, it’s achievable in many domestic environments. The Ampro antennas have proven their worth, but be mindful of cutting the elements correctly to avoid overheating issues.
Thanks for joining me on this journey! If you found this information helpful, please consider subscribing for more insights and experiments in the world of ham radio. Don't forget to check out some great deals on equipment, like the Yaesu FT-710 transceiver, which remains my go-to for HF operations.
Happy experimenting, and I look forward to sharing more with you in the next post!
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