Our new Loop Fed Array (LFA) antennas, phasing lines, and power dividers have arrived from InnoVAntennas. Our plan for this phase of our project includes the following steps:
- Build mounts for the stack Power Dividers
- Design and a mounting and truss system for the 3 Element LFA yagis in our stacks
- Build the first 3-element LFA yagis, test mount it on our Tower, and adjust the SWR
- Build the additional ten 3-element LFA yagis
- Build the 7-element LFA and adjust its SWR
We are using Power Dividers from InnoVAntennas to construct our three new fixed stacks.
These units are very well made and perform well, but they did not come with a system to mount them on our tower. I decided to fabricate mounting clamps to attach the Power Dividers to the legs of our tower.
The clamps are made using stainless steel U-clamps and 1″ square aluminum tubing.
The mounts worked out quite well, allowing easy access to the connectors on the Power Dividers for attaching coax cables. I made up three sets of clamps to mount the power dividers in our stacks.
3-Element LFA Mounting System
The 3-Element LFA antennas that we are using are a custom variation of InnoVAntennas 3-element LFA design. The antennas are designed to be rear-mounted to a pair of legs on a rotating tower. We are using the antennas on a fixed tower, and we want to be able to adjust the direction they point in. To accomplish this, I decided to fabricate an adjustable system suggested by Matt Strewlow, KC1XX, using a 1/4″ threaded stainless steel rod.
I began by assembling the boom and clamps for one of the 3-element LFA antennas and attaching it to our tower. This allowed me to fabricate and test an adjustable rear clamp to orient the antennas. The clamps and hardware are made from aluminum and stainless steel. The components came from DX Engineering and our local hardware store.
The final step in this part of the project was to install a small eye bolt near the front of the booms and create a simple clamp to attach a boom truss (dacron) rope and a turnbuckle to support the front of the antennas.
Once everything fit and worked properly, I made up 11 sets of mounting hardware to support all of our 3-element LFA yagis.
3-Element LFA Assembly and Test
The next step was to assemble the first 3-Element LFA yagi. These antennas are well-made and go together easily. I assembled the boom, mounting attachments, and the center of the elements in my shop and then moved the antenna outdoors to complete the assembly and final adjustments.
I attached and sealed the phasing lines to the driven elements and checked the SWR with the antenna pointing skyward. Next, I adjusted the length of the driven element loop ends to get each antenna’s SWR where I wanted it.
I mounted the first antenna on the tower to confirm that my mounting system worked as planned and to check the SWR adjustment with the antenna at its installed height above ground.
As you can see from the analyzer image above, the antenna tuned up very well.
The only real problem I encountered was finding enough space to store all 11 antennas after they were assembled and tested. As you can see from the photo above, we had quite an “antenna farm” in our backyard during this part of our project.
7-Element LFA Assembly and Test
The final part of this phase of the project was to assemble the new 7-element LFA yagi. This antenna uses a curved reflector to further improve its pattern and lower its noise temperature.
I had just enough room in our workshop to assemble the antenna’s boom, mast clamp, truss components, and element centers.
I moved the antenna outdoors, where we had more room to complete the final assembly, and attached the feedline. I adjusted the SWR of the antenna with the front elevated skyward. Final SWR and driven element adjustments were made with the antenna suspended about 30 ft above the ground on a tram line.
The final step in our preparations was to run control cables from our shack to the junction box on our towers to enable our microHam system to control the remote Preamp Housing and Antenna Switch.
The next step in our project will be to install everything on our towers and integrate all the antennas and components into our station.
We’ll continue to post more articles in this series as our project proceeds. Here are some links to other articles in our series about our 6m Antenna Upgrade Project:
- 6m Antenna Upgrade Part 1 – Plans for Antenna Enhancements
- 6m Antenna Upgrade Part 2 – High-Power Power Preamp System
- 6m Antenna Upgrade Part 3 – microHam Antenna Control System
- 6m Antenna Upgrade Part 5 – Antenna Installation and Station Integration
With all of our preparations complete, we are ready to install our new antennas on our tower.
I’m curious, do you really have enough boom sag that you need to truss the boom? I’m surprised that the square boom would sag like that on a short 3 element yagi.
This is a really cool design and I am excited to hear your results with the array.
Mike – KI8R
Thank you for reading our Blog. Think about what might happen as we get a load of ice and snow on these antennas. This is where the truss becomes important,
That makes perfect sense.