correct
The antenna is a full half wave dipole which has by definition a gain of 2.15 dB above a isotropic antenna (which is imaginary because it can not exist in real world.)
2 meter of RG174 gives - 0.6 dB
So the gain is 1.55 dBi (2.15-0.6) so the claimed 5.4dBi is a fantasy which I would not expect from a product sold by Digikey
see: https://www.sciencedirect.com/topics/engineering/isotropic-antenna for the mathematical background
look nice …eny link cooliner antenna calculation … i need fo 433 Mhz ?
thanks
I’m intrigued. Can you shared the construction details and measurements?
I am equally happy with all of these for portable or fixed devices:
Taoglas FW.86.B.SMA.M e.g. from FW.86.B.SMA.M | Taoglas Antenna, ISM, 850 … 890 MHz, 240mm, 3.5 dBi, Male SMA, Screw | Distrelec International FW.86.B.SMA.M | Taoglas Antenna, ISM, 850 ... 890 MHz, 240mm, 3.5 dBi, Male SMA, Screw | Distrelec International
Technikkram 868MHz 7dBi External Antenna https://amzn.eu/d/bmqdd5a
Eightwood 868 MHz Antenne Kipp-und-Schwenkbar https://amzn.eu/d/2bL4Wx5
For non-portable devices further suggestions on request.