I ordered a Nagoya UT-106.
In the past I owned a similar dualband antenna, but with just one coil, so I can do comparisons. The very first impression is that the base is too small. The UT-106 base is as large as 2€ coin and purely circular, while the older was slightly larger and had three small protruding feet that helped stability.
A smaller base means a smaller metallic area that couples with the car body (reflector or ground plane). Also the antenna oscillation is more likely to snap everything off the car in a bump or just at highway speed.
So I tried the magnet on pure iron. Weak. Too weak. Wobbling the antenna radiator caused the whole base to jump back and forth. I will not mount this antenna on my new-ish car and drive around!
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With all these "bugs" I will not even try it on-the-air.
I know the old say "you get what you pay for". I was prepared to do some improvements, but this is probably too much to fix.
My review: don't buy it.