toroid frequency response and number of turns

In the short wave frequency range 1 turn can made a big difference.

The core material can make a big difference too.
The first choice to make is the core material?

The calculator give the frequency range for the material. The circuit under development is operating at 2 Mhz so the 77 material could be a good choice.
The next question is what will be the input Z. The rule of thumb is the primary should be 4 times the input Z. So with a 50 Ohm system we need a 200 Ohm primary. The next question is will we use a diode ring or feed a Jfet mixer?