H field measurements with waveguide twist

I am trying to get the value of the h field with a horn antenna as a reference antenna. I used a 90 degrees waveguide twist with the horn antenna in preset to measure le level of the received signal. But I am getting strange values.

Am I proceeding the right way to measure the h field? If yes is it a scaling issue if the values that I?ve got? If not how can I measure the h field knowing that I only have a stage ratatiné in the E filed?

Thanks!