I measured my completely factory standard FX-3 ELT antenna today. I used an MFJ antenna analyzer and a Vector Network Analyzer. The MFJ has limited frequency range but the VNA was set to sweep 100 to 500 MHz.

The results for 121.5 can only be described as horrible. At 121.5 MHz the antenna shows an SWR of 4.4:1. The closest resonance is actually at 108.8 MHz where the antenna has an SWR of 2.5:1. The results for MFJ and VNA showed good agreement. The fact that the resonant frequency is lower than the design frequency is consistent with the supposition that the bracket makes the antenna electrically longer.

It looks better at 406 MHz where the SWR according to the VNA was 1.5:1. This may explain why CubCrafters live COSPAS/SARSAT test was satisfactory.

I would like to hear what measurements CubCrafters made on the ELT antenna. It's hard to believe that anyone with any knowledge of antenna theory or practice could have designed such a poor installation.