I measured this antenna with my VNA. It's a single frequency antenna; there is a sticker on it: 315/433MHz. It is actually tuned at about 350MHz; vswr of about 1.2 and impedance 50 Ohms. At 315MHz vswr is 2.3 impedance is 27 Ohms. At 443MHz vswr is 4.0 impedance is 85 Ohm. So actually this antenna is not fit for purpose.
I measured this antenna with my VNA. It's a single frequency antenna; there is a sticker on it: 315/433MHz. It is actually tuned at about 350MHz; vswr of about 1.2 and impedance 50 Ohms. At 315MHz vswr is 2.3 impedance is 27 Ohms. At 443MHz vswr is 4.0 impedance is 85 Ohm. So actually this antenna is not fit for purpose.
I'm not sure how this antenna is supposed to work (i'm not antenna expert). If you open it up it contains a pcb. See my previous comments and pictures with measurements. I had more but can only attach 5 pictures. The 15dBi certainly is not true.