The first tin didn’t have enough metal to make a proper length image element. For optimum results, the groundplane needs to be at least as long as the driven element. Longer is OK. Mag mount antennas perform well on a car roof. (which was suggested by belzybob.
The mag mount antennas included with most of the SDRs aren’t very good. Some of them are downright horrible. The worst part is the feedline. Small diameter coaxial cable, e.g. RG-174 is some of the lossiest stuff made. I noticed the coil of feedline in your picture. As lossy as the stuff is, even a moderate length of it isn’t doing you any favors. True the loss may not be large, but with the DSP the SDRs do, sometimes the difference between receiving a signal and not is only 1 or 2 tenths of a dB. Feedline is to an antenna like a speaker is to a good audio receiver. Even if you have a top-of-the-line receiver, if it’s connected to lousy speakers, it’s still going to sound lousy. Same with the antenna. Connect a good antenna to lousy feedline and your antenna performs lousy. It’s hard to beat the good stuff, e.g. LMR-100 or any of the other LMR coaxial cable series.
I once again tried a metal lid, and I also tried a paint tin but they both reduced performance.
At this point, it sounds as if the metal lid improved the input to the preamp to the point the preamp was overloading your receiver’s front-end, hence the performance drop.
The taller can works because even though its diameter is too small, the vertical length of the can is sufficient to make the image element. Much the way the radials in abcd’s third picture are positioned.
(where the radials are parallel to the feedline)