Below you will find a proposal to form a community to develop what has been termed the “BatBeam”.  The BatBeam is a multi-band, high-gain, software-defined Yagi antenna being developed as a free, open-source project. The goal is for a group of us amateurs to collaborate on the design, development, testing and production of these antennas together – both to advance the state of the art, have fun and learn some new technologies together doing what we like to do. I am envisioning that the core team will meet online via weekly screen sharing meeting using HF and/or Internet audio (depending on everyone’s location and propagation conditions).  So far, there’s been quite of bit of early interest – and we’re just getting started.

“So what?”, one may ask… why should anyone care about a new Yagi antenna design.  We have plenty of options to choose from today.  Good question!  Here’s why:

The BatBeam multi-band Yagi and Bat-V Dipole are Software-Defined Resonant Antennas (SDRA) that address some of the biggest drawbacks we see with typical alternatives today:

  • Multi-band operation without separate elements required per band
  • No mechanical moving parts to break down
  • Lower cost to build (hundreds of dollars)
  • Lower weight and mass – easier to handle and manage
  • Lower wind load – mount on masts as well as smaller towers
  • Higher gain with more elements
  • Instantly tunes to resonance
  • Auto-tunes to resonance by sensing RF frequency and automatically adjusting element configurations in a matter of milliseconds
  • Remotely managed – no controller box required inside the shack
  • Battery / solar power option – low-power operation enables solar power

As a bit of background, earlier I posted an idea for advancing the state of the art around self-tuning, resonant antennas.  After sharing a video and blog post explaining the original “BatBeam” concept with one of the communities I am a member of here, it was brought to my attention that there are patents covering aspects of the original BatBeam invention.  Upon further research, I was able to confirm that appears to be the case.  As a result, I withdrew the original video and related proposals as this approach did not allow us the freedom to innovate and promote our project’s results properly.

Given that I and others are passionate about development of these high-gain multi-band antennas and related concepts, as part of our pursuit of amateur radio, I decided to release these ideas, concepts and inventions to the public for use by everyone (versus attempting to patent or otherwise create proprietary products or works).  As indicated in the attached invention disclosure, anyone is free to pursue these ideas for personal or commercial use, with the only restriction being proper attribution in accordance with the Creative Commons 3.0 Attribution License.

Please take a few moments to review more details about the project. If you are interested in tracking our progress, then you can register at the end of this blog post. If you would like to become a member of the project team, please email me directly:  rick (at) w5fcx (dot) net.

BatBeamRev1 (click link to download the PDF – register for updates at end of this blog post)

The attached “Rev 1” of the BatBeam proposal is to document the goals, objectives and what is possible as a community effort to develop a new type of multi-band high-gain antenna – the BatBeam, and its cousin, the Bat-V Dipole, a “natively resonant” multi-band dipole. Natively resonant antennas require no tuners for low-SWR operation.  The BatBeam and Bat-V Dipole antennas are examples of Software-defined, Natively Resonant Multi-band Antennas, whereby intelligent controllers sense the RF signal and automatically tune the antenna to resonance.

Here’s a copy of the original hand drawing design (click on the link to enlarge).

If you are familiar with the Spiderbeam design, which is available from spiderbeam.com, you will note some similarities.  The BatBeam is an evolution of the Spiderbeam design, using fiberglass poles, Kevlar supports, and a spreader system that allows many wire elements on a single, lightweight beam.  The Spiderbeam exhibits excellent gain characteristics; however, like most multi-band Yagis, it consists of many monoband elements spread across a single boom. One difference with BatBeam is each element is multi-band, so fewer wire elements are required for multi-band operation and if you want to deploy more elements, then higher gain should be possible.

The architecture diagram below shows the main components of the BatBeam.  On the right, we see an Arduino-based element controller, which manages the antenna resonance switching via a series of J-Box junctions.  Each J-Box is an addressable RF switch, that electronically modifies the overall antenna element conductor length for resonance on a given band.  Each antenna element consists of a series of conductors (e.g., antenna wires) which carry the RF signal. We call these “conductor segments”.  Each conductor segment is separated by a J-Box. The J-Box RF switch is opened/closed to electrically alter the antenna element length.  To create a Yagi antenna, a combination of these elements are combined on a boom, as shown in the PDF file and original invention disclosure hand drawing.

Due to the J-Box design, the Rev 1 BatBeam and Bat-V Dipole antennas should be capable of tuning to resonance in a matter of milliseconds, as there on no moving mechanical parts, unlike other prior art.  Instead, each J-Box contains a relay or PIN diode that acts as a switch which controls whether or not the RF signal is allowed to extend to the next segment.  For example, if all J-Boxes are in the “closed” state (signal is passed through the J-Box), then resonance would be at 20 meters when all of the J-Box and wire segments are combined.  To retune for 17 meters, the 20-meter J-Box is placed into the open state, resulting in near instantaneous tuning.  Similar instantaneous switching also takes place in Reflector and Director elements for the BatBeam antenna, a multi-band Yagi.

PIN diodes and relays have been used in numerous RF applications and are a proven means of switching RF signals today. During the prototyping phase, we intend to test both alternatives to determine the pros/cons of each in practical application.

Because each element and its J-Boxes are relatively small and lightweight, constructed from heavy duty wire and kevlar lines, the overall Yagi beam weight is a fraction (less than 50%) of traditional fixed Yagi antenna, and wind loads are up to 60% less. At the same time, it is also possible to build BatBeams with larger numbers of elements – perhaps as many as 8 to 12 elements, for record levels of antenna gain.

Another innovation is use of intelligent, microprocessor-based controllers using Raspberry Pi and Arduino technology, which is extremely powerful, inexpensive and reliable.

The result is a Software-Defined Resonant Antenna (SDRA) design that addresses the biggest drawbacks of most alternatives available today.

For more details, please download the PDF presentation file to learn more.

BatBeamRev1  (click the link to download the PDF file)

If you are interested in keeping up with the development of the BatBeam and Bat-V antennas and becoming a part of its community, please register below.

More as it develops.

73’s,

Rick / W5FCX

P.S. I decided to release the BatBeam and related inventions under the Creative Commons 3.0 Attribution License. This makes unlimited use of the inventions and any source code we develop under the BatBeam project freely available for both personal and commercial use.  From the outset, my objective has been to create a community of radio amateurs who are able to advance the state of the art, experiment and have the freedom to do whatever we want with the fruits of our labors, efforts and passion.