Roy Lewallen wrote:

A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has
roughly the same or a little higher total complex permeability than 73
over most of the lower HF range and same or higher than 43 on up to 100
MHz. So it should be a good ferrite to use for very wide band
applications. However, Table 1 shows that it's available in large parts
only. Type 43 is very widely available in a wide variety of sizes, so
you might have a lot more luck getting cores of the sizes you need in
type 43.

Roy Lewallen, W7EL


Amidon do stock some type 31 products, including FT-240-31 toroids and
the large beads for RG213, but they aren't listed on the website.

Part numbering is the same as normal, so simply substitute a "31" in the
part number you wish to order, and then call 1-800-898-1883.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek