Ferrite cored RF chokes in Class-E RF power amplifiers – core material issues

At Ferrite cored RF chokes in Class-E RF power amplifiers a design was offered for a choke using a Fair-rite 2843000202 core (commonly sold as a BN43-202), and the point was made that some products sold as BN43-202 might be significantly different.

Let's look at the calibrated model estimates of choke impedance and core loss, side by side.

The left hand chart is derived from Fair-rite 2843000202 data (as calibrated for SRF), and the right hand is the same but referencing the National Magnetics Groups H material permeability chart.

Though they are very similar in form, the core loss is quite different at lower frequencies, mainly a consequence of lower impedance components increasing magnetising current and its follow on effects. The solution is probably not to simply add another turn as that compromises Idcmax.

This is not to suggest that the H material is unsuitable, but it is less suitable, though it may work well enough in the application. Be aware of the source and applicable data from your magnetics supplier, and an imitator might have good product, but use their data to assess that.