I re-wound the coil this week with 18 turns (17 turns and 2 half turns, slightly smaller 14AWG .0591) and finally got the 40m band under 2.0:1 by adding 49 inches to the elevated radial (you were right)!
40M, SWR 1.9, 7.00 mHz
40M, SWR 1.6, 7.20 mHz
I can live with these results.
Now it’s on to Field trials on 40m to see how the contacts go.
Thanks for hanging in there Bob! I tested with a 17' Chameleon whip.
I've noticed quite a bit of variance depending on quality of ground and radials. It sounds like you found the "dip" at 17 turns, but the dip wasn't as low as you'd hoped. I understand. This might be a good time to experiment with extra ground radials, or trying a different location with different soil.
Did you test this with your whip? The best I could get with the original design was 2.2 to one. I took off a winding and it went to 2.5 then I went the other way to 18 windings and it went to 3.0 so I’m a little lost. Not sure how many iterations of this process will need to do, but I will keep trying..
I built this and it had 10.5µH of inductance. With my CHA SS17 whip fully extended it had the lowest SWR at 6.645 MHz. I needed to collapse two sections to get it resonant on the 40m band. I backed out one full turn of the winding to get 8.9µH. I need to test this with my whip but I'm surprised with this result. I would have expected needing more inductance with a 17' whip.
Your induction measurement is close to my own. I've had to tuck in more of the whip than I wanted to on occasion as well. Not every time, but it does happen. I usually attribute it to the quality of my ground plane and the [less than ideal] grounding qualities of the surface I mount the antenna on.
Thanks, Gary!
I re-wound the coil this week with 18 turns (17 turns and 2 half turns, slightly smaller 14AWG .0591) and finally got the 40m band under 2.0:1 by adding 49 inches to the elevated radial (you were right)!
40M, SWR 1.9, 7.00 mHz
40M, SWR 1.6, 7.20 mHz
I can live with these results.
Now it’s on to Field trials on 40m to see how the contacts go.
73s
Bob, WB0WIF
Thanks for hanging in there Bob! I tested with a 17' Chameleon whip.
I've noticed quite a bit of variance depending on quality of ground and radials. It sounds like you found the "dip" at 17 turns, but the dip wasn't as low as you'd hoped. I understand. This might be a good time to experiment with extra ground radials, or trying a different location with different soil.
Did you test this with your whip? The best I could get with the original design was 2.2 to one. I took off a winding and it went to 2.5 then I went the other way to 18 windings and it went to 3.0 so I’m a little lost. Not sure how many iterations of this process will need to do, but I will keep trying..
I built this and it had 10.5µH of inductance. With my CHA SS17 whip fully extended it had the lowest SWR at 6.645 MHz. I needed to collapse two sections to get it resonant on the 40m band. I backed out one full turn of the winding to get 8.9µH. I need to test this with my whip but I'm surprised with this result. I would have expected needing more inductance with a 17' whip.
Which type of Loctite would you suggest for this project?
Sorry for the late reply. I'm sure anything will work, but I use the red 271.
Thanks for sharing Pete.
Your induction measurement is close to my own. I've had to tuck in more of the whip than I wanted to on occasion as well. Not every time, but it does happen. I usually attribute it to the quality of my ground plane and the [less than ideal] grounding qualities of the surface I mount the antenna on.