Below some photographs of my 300 KHz to 5 MHz coupler. The coupler is build on a Philips core. Probably the TN 36/23/15 3C90 material. The sizes match and the colour is blue.
For more explanation see the article about the coupler from 1.5 – 30 MHz.
This was available in my junk box. 32 turns on the toroid.
The measurement on my sweeper / analyser, the directivity is quite good (>30dB).