Hi Dianne,
What model/version of the nanoVNA do you have? many do not cover the 2.4GHz bluetooth frequency band.
What diameter/type of coaxial cable are you currently using? Type RG316 has diameter 2.5mm and RG178 diameter 1.8mm.
My advice is to test your antenna with a length of cable that will be used in the final product with a connector that will be used in that design.
I hope the above is of some help to you
Kind regards
Ed
