Hi all,
one problem I always had with my vertical antenna prototypes is that the SWR varies significantly with the type of ground and the deployment. This might not be a problem for KX2/KX3 users with an integrated ATU, but for my MTRs, it is.
So far, I mostly used 1-2 elevated radials, sloping loosely from the feedpoint ca. 80 cm above ground. Tuned in my yard, it worked well on rocky summits. But on Texel island in PA land, it did not match without an ATU.
I used elevated radials for they are said to be way more efficient. Now I see that this new design uses relatively short ground radials.
The unreliability wrt SWR depending on the installation has reduced my interest in loaded verticals, despite the big advantages in terms of deployment on small summits.
Can anybody comment on whether the ground radials approach, taken in this new antenna, is less dependent on the type of soil?
BTW, my last approach was to make an Elecraft T1 integral part of the vertical SOTA antenna, based on the respective mount released as a 3D printable design.. The downside of this is that
- Tuning takes time.
- Tuning puts stress on the MTR PA.
- If the T1 fails, so does the activation.
What I am considering now is using a 12 step rotary switch and respective taps on the coils instead of two slide switches that shorten the entire coils, so that
- you can mark the default positions for 20, 30, and 40m, but
- you can still vary the inductance in order to optimize the SWR.
This will be a bit bulkier than the 2-slide-switch design, but way more flexible and more robust that a T1.
73 de Martin, DK3IT
PS: I might add a common-mode choke and a Dan Tayloe, N7VE SWR indicator to the design.