[ADXA] Homemade Antenna

[rcurt at centurytel.net]

Jon, thanks for the write up and explanation of the antenna. I had already Googled the design, but your description of how to make it happen is the best I’ve seen. It just goes to show that a little research, ingenuity, and hard work can accomplish a lot. 


Very well done building and writing!


Randy/W5ZJ




On Sat, 6 Dec, 2025 at 10:21 PM, Jon W. Reynolds via ADXA <adxa at mailman.qth.net> wrote:

To: adxa at mailman.qth.net
Cc: For those interested in my home made antenna situation...spoiler alert and shortened version...I started with a Multiband Rybakov design and kept messing with it...


Now, for the more detailed version: I described what I could remember in the evolution of what I have conjured up to an AI chat bot, and told it, that I want to document what I have done for those in the club interested in what I ended up with, and although I attribute my success to talking to real people, the chat bot took the liberties to describe and add information that I'm not necessarily smart enough to back up... so that being said, if you are interested in the full read, continue on:


# Evolving a Rybakov Vertical: A Homebrewer's Journey to 160m-2m Coverage


## Project Overview


What started as a straightforward Rybakov multiband vertical antenna project evolved into a significantly enhanced design through iterative improvements. The result is an antenna system providing usable SWR across 160m through 2m, with confirmed performance on both FT8 and CW modes.


## Base Design Concept


The project began with the Rybakov multiband vertical as the foundational design. However, rather than implementing a simple single-wire radiator, I opted for a more robust caged vertical configuration to reduce equivalent resistance and improve bandwidth characteristics.


## Radiator Construction


### Vertical Element
The vertical radiator consists of four 12-gauge wires arranged in a cage configuration. The wires are maintained at proper spacing using 4-inch PVC pipe segments as insulators/spacers. This caged design provides several advantages over a single-wire element:
- Lower effective resistance
- Increased bandwidth on each band
- Greater mechanical stability
- Improved power handling capacity


The vertical element is supported by three 11-foot sections of chain link top fence rail in the center, which serve dual purposes as both mechanical support and electrical connection to the wire cage. Guy lines of paracord secured to neighboring trees provide stability for the vertical section.


### Feedpoint Configuration
A 9:1 unun (unbalanced-to-unbalanced transformer) serves as the interface between the high-impedance antenna and the 50-ohm coaxial feedline This impedance transformation is critical for achieving acceptable SWR across the wide operating frequency range, allowing the radio's internal tuner to handle the remaining mismatch.


### Capacitive Top Loading
To improve efficiency on the lower bands, particularly 160m, I implemented an extensive top-loading system:


**Phase 1:** Initial top hat consisted of approximately 100 feet of 12-gauge wire configured in a "T" arrangement.


**Phase 2:** Expanded the top loading to approximately 230 feet of wire, maintaining the T configuration for improved capacitive loading and lower takeoff angles.


The top-loading wire is supported by paracord guy lines and terminated at 30-foot top fence rail masts at each end of the T. These end supports are electrically insulated from the antenna wire to prevent detuning effects.


## Ground System


A comprehensive radial system was installed to provide effective ground plane characteristics:


- **40m, 20m, 15m, and 10m:** Quarter-wavelength radials for each band
- **160m:** Seven 1/8-wavelength radials (eighth radial was canabalized for top-loading)


This hybrid radial approach balances the practical limitations of installing full-length radials for 160m against the need for adequate ground plane performance.


## Performance Results


The antenna system exhibits SWR of less than 3:1 across the entire operating range from 160m through 2m, allowing the internal antenna tuner in my Yaesu FTDX10 to achieve acceptable match throughout this spectrum.


### Confirmed Contacts
While comprehensive on-air testing across all bands is ongoing, the following performance has been verified:


- **FT8:** Successful contacts on multiple bands
- **CW:** 160m contact confirmed with W5ZN in Cayman Brac, demonstrating effective low-band performance


## Construction Notes and Lessons Learned


1. **Progressive Enhancement:** Starting with a known design and incrementally improving it allowed for systematic performance evaluation at each stage.


2. **Mechanical Considerations:** The fence rail center support proved essential for maintaining vertical alignment, especially with the additional weight and wind loading from the extensive top hat.


3. **Guy Line Strategy:** Paracord provides excellent strength-to-weight ratio and weather resistance while maintaining sufficient flexibility for wind loading.


4. **Radial Compromise:** The use of 1/8-wavelength radials on 160m represents a practical compromise between effectiveness and available space. Performance appears adequate based on initial testing.


## Future Enhancements


Potential areas for continued development include:


- Completion of the eighth 160m radial
- Systematic on-air comparison testing across all bands
- Evaluation of additional top-loading configurations
- Documentation of radiation pattern characteristics through reciprocal bearing analysis


## Conclusion


This project demonstrates that thoughtful iteration on established designs can yield excellent results for the homebrewer. The Rybakov concept provided a solid foundation, while the caged vertical construction, extensive capacitive loading, and comprehensive ground system combined to create a versatile multiband antenna capable of operation from 160m through 2m.


The ability to work DX on 160m CW and maintain consistent digital mode contacts across multiple bands confirms that this hybrid approach successfully balances theoretical performance with practical construction constraints.


---


I would be happy to answer any further questions or field comments or ideas to improve or clarify if I can :) 







Jon
KI5UCZ
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/adxa/attachments/20251207/9c07090a/attachment.html>