Semi-Rigid cable soldering

(1) Soldering a little bit at the front of cable for ground contact
(2) Soldering half of cable for ground contact
(3) Fully soldering btw cable and PCB GND

I measured impedance by the way (1) (2) & (3) and they all got similar
measurement results. Frequency ragne is below 2GHz. I'm confused about it
seems the way (3) is the most standard way for measurement but how come
the way (2) & (3) got similar measurement result compared with the way (3) ?
According to your experience, what effect will be resulted in according to these 3 different ways? How to explain its effect ? Which way you are used to doing
measurement ? Thanks for your help.

Anyone can share your opinion ? Thanks a lot.

All the ways you did are quite correct, as your care is in ground connection. In fact no big differences are among them. If you want to go up in frequency you should take care in transition between coax and planar transmission line. The limit will come there.
I hope it can help.
Mazz

Thanks.
Does that mean the GND connection btw semi-rigid cable and PCB
are not so important ? I'm confused about that people are always
saying that consistency of GND connection is important in RF but
from this measurement it seems not. How do we explain it ?
Thanks for your help.

Ground connection is really important. I think that all 3 ways you did it are OK, and measurements proves that.
Mazz