Jon,

When you assembled the A3S, did you use the lengths show in the assembly instructions?  For Phone, Center or CW?   Do you have a Balun at the feed point?  What length and type of coax was between your Antenna Analyzer and the feed point for the measurements you made? Unless the feedline is an electrical half wave length (or multiple of ½ wavelength) at the frequency being tested, what you see on the analyzer is not what the impedance is at the feed point.  Did you see a SWR dip (minimum) on 15 and 20M?  The adjustment distance difference between CW and Phone are pretty small.  If you have a resonant point out of band you could look at the delta in frequency (measured resonant freq versus desired freq…Center of Band) and then look at the distances on the installation instruction table between band segments and get a rough idea how much to adjust the lengths.   If you are confident that your assembled lengths are close to the instruction manual lengths I’d be suspicious of the traps.  You might do a wide sweep from about 12MHz to 32MHz and look at the results….you should see SWR dips at somewhere around 14, 21 and 28MHz.   

10M looks OK….the first traps(away from boom)  should look like a high impedance on 10M..and apparently they do. The second set of traps should have a high impedance (parallel resonance) on 15M.   On 20M both traps should look like loading inductors…making the 25ft total driven element resonant on 20M (around 33ft).   You can test the resonant frequency of traps using a antenna analyzer…you can do a direct connection but the analyzer will load the tuned circuit.  If you use a small pick up coil (like used on grid dip meter) you’ll get better results.  I haven’t tried it but a small nanoVNA would probably give decent results on HF with a direct connection?  Google/AI is your friend.

It’s been a while (80’s?) since I had a trapped tribander…a four element Wilson of some variety.  It was fairly narrow banded but was good enough to cover the full bands without a tuner. ..less that about 2.5:1.

One of our real antenna experts can probably provide better guidance.

Good Luck/73,

Pat, W5VY

From: [email protected] <[email protected]> On Behalf Of Jon W. Reynolds via ADXA
Sent: Saturday, January 10, 2026 9:41 PM
To: [email protected]
Subject: [ADXA] Woof woof (silent woof)

Long Tower Saga update:

2 out of 3 woofs (I'm guessing). The Saturday tower fairy came out and we were able to accomplish much more work on the tower project! We now have a rotor that turns the antennas from the shack! 

We still have a little bit of work to do in the tri-band A3S. Because I'm new to tower work,  I prioritized things a little backwards. I got the antenna assembled and up (while the help was in town), before I checked the swr, and it is a little off. I also tried not to crimp the antenna boom with the u-bolts, and they are loose enough to sway a little. So...there is still some work to be done, but I have the rotor system up and working. 

The SWR Readings as I show with the Amazon nano vna:

20m 14.000-14.350

SWR 3.77-2.61 wedge shape (high to low)

15m 21.000-21.450

SWR 3.45-3.68 slight wedge shape (low to high)

10m 28.000-29.700

SWR 1.13-1.75 (slight wave shape)

My plan is to suspend the antenna from above on the mast pole, unbolt the antenna from the mast, and rotate it to 90° so that I can reach the loose elements. I'm thinking to address the swr problems, I'll extend the tips of the of the reflector and driven element 1/2" and re- mount everything and check the results. 

I'm open to suggestions if anyone is forthcoming with knowledge/technique or experience with a cushcraft A3S and tuning it a little. 

73

Jon

KI5UCZ