So with the help of friends and family, I have a really nifty looking antenna setup. Seriously I keep looking at it everytime I walk out in the yard.

I love seeing this majestic monument to Ionosphoros (God of the Sky Bounce) The bearded titan who lives in the F-layer. When he’s in a good mood he gently curves your 20m signal around the planet for a perfect 5-9 into Japan. When he’s hungover (usually after a solar flare), he just shrugs and your DX disappears into the void.

I spent a day or so putting ends on coax and getting antenna switches and rotators connected and then the SWR testing commenced. Here is where we find out if GROK was right about the resonance frequency shifts or if I am scheduling a man-lift delivery to go up there and fix some things.

If you’re just joining us, this is the 4th installment in my saga. I inherited a beat up old Cushcraft A4 (not an A4S, this thing is probably from the 80s) tri-band antenna from a club member’s estate Bob Galloway, W5ACE (SK). Over 2 years I got it back assembled and all parts repaired and adjusted, and finally have it mounted on my tower.

Part 1: IT’S A TRAP! – I finally tackle the testing of the traps and learn a lesson about fear.

Part 2: It’s Alive! … ALIVE!!!! – I pull apart all the traps and clean and adjust everything I can get my hands on.

Part 3: Raising my Cushcraft A4S Tri-bander – I make some predictions about resonance shifts with the help of Tibetan monks and raise the antenna with the help of my Oompa Loompas.

Well, so here I am. I have probably 60 lbs of weirdly shaped aluminum 35+ feet over my head and I have to finally answer the question…. Is this thing a useable antenna or is it just an expensive lawn ornament? Grok assured me I was doing it right. He promised me my antenna would adjust itself into the bands as it is raised nearer to its sacred deity Yagius the Director.

For those that don’t know, Yagius the Director is the mighty multi-element war god with a huge parasitic array on his back. He focuses your signal into a laser-like beam so you can smash pile-ups. Loves forward gain, hates side lobes. His eternal enemy is Rearlobus, the sneaky god of back lobes who steals your power and gives it to the guy behind you.

Finally getting measurments

Now with ends on all the cables and everything connected up, it was finally time to measure this thing up and see how well I got everything adjusted. I grabbed my trusty NanoVNA and fired up the software and setup a sweep on each ham radio band starting with 30 meters.

30 Meters

Nice! On the ground I had a resonance at 9.835 Mhz and I expected 100khz to 200khz shift when the antenna was raised to full height. This look pretty much exactly like what I expected from the predictions and I am more than happy with this result. My VSWR is less than 1.5:1 across the entire 30 meter band. But what about the rest of the bands?

20 Meters

BOOYAH! This is nearly perfect! from my calculations I was expecting to see my resonance closer to the high end of the band (around 14.270) which would have been a little too high, but I was very pleased to see this resonance dead center! I have barely over 2.0:1 at the extreme low end of the band.

15 Meters

Double BOOYAH!!! So the measurements on the ground and AI predictions placed this resonance at between 21.135Mhz and 21.235Mhz. Well, look at that! pretty much exactly at the higher end of that prediction. Looking back, they all were right at the high end of the predictions. Again, this antenna is 100% perfect SWR. I can’t imagine making this better with any adjustment.

10 Meters

Not quite Triple BOOYAH!!! Say maybe 2 and 2/3rd BOOYAH!! This didn’t drift up nearly as much as the other bands, and that’s a shame. if it had shifted another 100khz or so I would have had <3.0:1 VSWR on all bands. As it stands I am 100% satisfied with these results! I’ll have to break out a tuner if I ever want to transmit between 29.550 and 29.700Mhz. I think I can live with that!

I also have an Alpha Delta DX-DD 80/40 dipole and a Sirio 50-3 6m yagi on this tower. Here are their plots in case anyone wants to see them. I have never had such a well-tuned antenna system! I have basically turned off the internal tuner on my ICOM IC-7300. It is a joy to operate. I’m currently working on an arduino rotator controller so I can set up a Raspberry Pi running rotctld and have automatic antenna control right from my logging software.

Alpha Delta DX-DD – 40 Meters

Alpha Delta DX-DD – 80 Meters

15m VSWR Plot on tower

They say you can tun up a 40m dipole on 15 meters, I’ll give it a shot.

Meh, it’s better than nothing I suppose.

Sirio 50-3 – 6m 3 Element Yagi

Conclusions:

So what do I have? I have a perfectly functioning Triband trapped 3-element beam up 36′. Above that I have a 3 Element 6m beam at 42′. It also has near perfect SWR curve just where I want it. Alongside the tower I have an Alpha Delta DX-DD 80/40 dipole as an inverted Vee. It is a little narrow on 80, but that’s fine, it is loaded after all. It is performing very well and I am learning what this “Gain” thing is. There is something magical about seeing a spot on the DX cluster, tuning in and spinning beam and hearing a signal slowly come up out of the noise. I haven’t run into a situation yet where I had to spin the beam in order to null out an interfering station, but I’m told that it is cool when it happens.

Moreso, I know that I can climb my tower now and work on the antennas. I have the equipment and skills to get it done if need be. Also I have learned there is nothing mysterious inside a Cushcraft (or any) antenna trap. It’s just wire and aluminum.

Also I learned that being patient and careful when building an antenna, taking time to get every measurement exactly correct and triple checking everything will likely reward you with a perfectly tuned antenna. I used AI to guess at the effect of raising my antenna from ground level up to the full height. In the early days of the internet a person learned really quickly how to search for information. Your search queries had to be very precise to get exactly what you were after. Today’s AI engines are very good at digesting information, but one still has to be very precise in their queries to get the needed evaluation. I can see myself using AI for many more ham radio related tasks.