No, I did not measure these whips with any equipment. I dont have a VNA. The equipment I have measures only SWR/impedance, but does not measure Gain.
I have however compared whips: (1) standard stock whip of dvbt dongle, (2) same, but removeable part cut to 52mm, & (3) coiled whip like @ClarenceDold has. Here is the test setup and results: