Finally, I had some time to try out my homebrew vertical. I set it up in my garden and measured the radial wire. I got around 25m of wire, I wound it on a wire winder to 5m which corresponds roughly to a quarter-wave of 20m. Soon I found a nice SWR on the coil and then fine-tuned the radial. I was quite euphoric!
The bandwidth of the antenna was good in this band. But soon the struggle began. I could not find any good tune on lower bands. On 40m the resonant frequency was very narrow. I tried to tune the radial on every possible way, the coil, nothing
I am not sure what is wrong, maybe the common-mode current is making me trouble, I don’t know. I abandoned the project now for a while until I get a batch of toroids to make a decent HF common mode choke.
I thought about making a linked radial, like the wires on my dipole for quickly changing the bands. But honestly, why bother. Using an antenna tuner and just a simple piece of wire thrown up in the tree does the job. I recently even just took a 5m long wire, hung it up directly from my tuner vertically and attached 20m of one ground radial on the ground. I made a QSO with Brazil and Washington. Just like that 😎
Although the whip and the coil look very nice and powerful, I am rather disappointed with the result. But, I will not give up on this project, just postpone it for a while. Still waiting for short whips from China to start a project on 15/20/40m small MFJ Walkabout clones for my FT-817.