Attempting to reconcile W5DXP & G3TXQ’s comparison of K and 52 mix ferrites

Steve (G3TXQ) posted a graph comparing Cecil’s (W5DXP) measurements of two turns on FT240-52 and FT240-K.

It is interesting to reconcile the #52 curves with Fairrite’s datasheets. A simple reconciliation is to compare results at the frequency where µ’ and µ” curves cross over. Continue reading Attempting to reconcile W5DXP & G3TXQ’s comparison of K and 52 mix ferrites

Ferrite K mix

Among forum experts, there are ready recommendations for the ideal ferrite material (or mix) for a balun, often without knowing any detail of the application.

The ‘magic’ mixes include K. Perhaps they are devotees of Sevick.

Over some years I have searched for manufacturer’s data on K mix, and found only two references:

  • Amidon who give a very brief table summarising characteristics, inadequate for RF inductor design; and
  • Ferronics who give characteristic curves, albeit in less common format.

Problem is that Ferronics µi is 125 against Amidon’s 290… so their K materials are different.

One has hoped that an interested competent person might have made measurements of some samples from Amidon to give full characteristic curves, it isn’t that hard. Continue reading Ferrite K mix

What does an Antenna Tuning Unit (ATU) do?

An Antenna Tuning Unit (ATU) performs a simple but important function in many transmitting systems.

Almost all things called an ATU are simply impedance transformers, and almost always, narrow band impedance transformers (meaning that when adjusted, they achieved the desired transformation over only a narrow frequency range).

Screenshot - 03_05_2014 , 15_06_33

ATUs come in a range of configurations, each designed for a specific set of characteristics. Above is the heart of a Palstar AT2K T Tuner, just three real passive components that are fully explained by conventional linear circuit theory. Continue reading What does an Antenna Tuning Unit (ATU) do?