Antennas On The Tower – Part 3 (System Complete)


Final Tower

Final Tower

Well, after several more days of intense work, our new tower and antenna system is complete! The work this week began with the installation of our Second SteppIR DB36 Yagi on the tower. Matt and Andrew from XX Towers made short work of this step. We began by rigging the second DB36 at the base of the tower and we removed one set of guy lines and replaced them with temporary guys so that we could pull the large yagi straight up the tower.

SteppIR DB36 Number 2 Ready for Tower

SteppIR DB36 Number 2 Ready for Tower

We removed the 6m passive element that is closest to the center of the antenna (and therefore the tower) before pulling the antenna up the tower to avoid damaging it. Once the antenna was up to the 60 ft level, Andrew positioned it on the K0XG Ring and clamped it in place. The following picture shows the DB36 installed on the rotating ring. Next, Andrew installed the phasing line from the lower beam to the Custom Feedline Breakout System at 80 ft and he also ran the control cable for the second DB36 to the base of our tower. This completed our 4 over 4 array system.

Up The Tower

Up The Tower

I did a quick test using the SteppIR Controller and confirmed that the second DB36 was working correctly. Its SWR performance is slightly different that the upper antenna on the lower bands. This is, no doubt, due to the large antenna’s closer proximity to the ground. We also found that we had a defective position sensing pot in the K0XG Ring. Fortunately, Matt had a spare and returned the following day to replace it. With this fix, the ring worked fine. Here’s a video of the second antenna turning around the tower on the ring.

To create clearance for the lower antenna, we modified the 80m Delta Loop that was installed previously into a diamond. This moved the resonance frequency of the loop somewhat higher so we removed a few feet of wire to bring it back to the center of the 75m DX Window.

We also built a 160m Inverted-L antenna. Since my SteppIR BigIR Vertical antenna was previously located only a few feet from the tower, I have a radial field and base plate that could be reused for the 160m antenna. The radial field consists of 48 buried radials each 85 ft long. The existing radial field was built using a DX Engineering Radial Plate. We rigged a wire up from the connector on the plate to one of the Phillystran guy lines on the tower and then ran the wire up along the guy line to form the top of the inverted L. After some checks with an antenna analyzer, we determined that the antenna needed a little bit of base inductance to resonant at the right spot in the 160m band. Matt had a suitable core available so we build a simple inductor and connected the antenna to the connector installed on the DX Engineering radial plate. The antenna was completed with a short length of LMR400 UltraFlex coax to the DX Engineering Remote Antenna Switch on the tower.

160m Inverted L

160m Inverted-L

With this step done, our new antenna system is complete! We managed to cover all amateur bands from 160m through 70cm (except for 1.25m) on a single tower. I have some cabling and finishing touches to complete to put everything into operation. One step that is done is to complete the shack entry cabling and water proofing. Here’s a picture of the results of that step.

Final Shack Entry

Final Shack Entry

I did  little testing on the SteppIR array on 20m and on the modified 80m loop. The array is very strong on 20m – it produced some really good signal reports including on report of 59 + 60 dB into LA, USA (about 1,400 miles from me). I have also gotten many signal reports from Europe in the 59 + 10 db to 59 + 30 db range. All good signs. I am also seeing some effective gain (about 5 – 10 db) on 40m. This is probably more due to the lowering of the takeoff angles and tightening of the vertical pattern due to the array than stacking gain. Also, the ability to use the array with the two antennas out of phase is great for close in work and for filling in holes in the pattern.

The 80m loop is better in the diamond configuration than as a Delta Loop. It now has a little wider bandwidth and is more omnidirectional, covering Europe more effectively. I don’t think a second loop facing Europe will be needed at this point.

Tomorrow will be a day to get the 2M and 70cm on the air, waterproof the tower side of the feedline conduits and tie up loose ends. I will try to post some additional operating information as well.

– Fred (AB1OC)

One thought on “Antennas On The Tower – Part 3 (System Complete)

  1. Congrats, and thanks for the video! I’m not familiar with tower rotors, but the speed of rotation for such a massive antenna is impressive! Also liked the effect of the leaf falling during the video!

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