A small ferrite toroid for use in baluns and line-isolators. This is 31-mix in the smaller 1.14" (29mm) size - unfortunately, 31-mix is not available in the more common FT140 (1.4") diameter.
9 turns of RG174 or RG316 make a great "resistive" balun/choke for 3.5-30MHz - this is ideal for QRP operators who favour the lower bands or require a small balun box. If you regularly run 100w "full duty-cycle" (ie: datamodes) then we suggest adding a 2nd core or consider the larger FT240-31 ferrite.
Need help choosing a ferrite? See our page on selecting the best size/type here.
Toroid sizes/types are easy to ID, the "114" translates to 1.14" (diameter) and the "31" is the ferrite mixture. What type do you need? 43 is good from 7MHz and up (and a good general-purpose 7-30MHz solution), 31 is better if you use the lower HF bands, 61 is good for an UnUn, while 75 is good for VLF projects. Remember, you can stack the cores for increased choking and power-handling. As always, ratings need to factor in the aerial (SWR) match and duty-cycle..