I was asked a very justified question, how well the DCTL-antenna would actually work. To test this, I was running the spectrumlab-grabber on a full-size vertical for 30m. The vertical is made from flimsy speaker twin-lead, cut to a length of 7.2m; both leads parallel. The vertical got two radials, made from the same stuff, cut to the same length. A telescopic fishing-rod keeps the vertical vertical.
On the left side of the following spectrum, I can see a spectrum taken with the vertical, the spectrum on the right hand side is taken using the DCTL.
It is somewhat obvious that the vertical delivers more signal. In terms of signal to noise ration, the DCTL is in a 3dB lead. Well, the slightly better S/N-R is not really visible, since I run WSPR parallel to SpectrumLab, it was actually measured. You may however get the impression that the FSK signal on 10140060Hz is somewhat clearer when the DCTL was use.
I have to add that the DCTL is placed next to a wall, the distance I would estimate as 20cm. With the DCTL not being proximate to other objects, and may somewhat higher, signals would probably be much better. Something still to be investigated.