In article ,
"Jeff" wrote:

Im confused regarding the choice of iron powder toroid for a 7Mhz high pass
filter. I need to use a small size (T68) toroid. For the freq range, some
reference texts say T68-2 is the one, others say T68-6" grade. I see
differing "best Q range" specs for the 6
grade.....2-30Mhz......10-50Mhz...etc.
Have similar need for 20Mhz LPF, but assume "6" is really the choice there.
Any suggestions as to the relative differences and reasons to choose between
grades 2 and 6 for the HPF in T68 size?


Either grade 2 or 6 should work fine at 7 and 14 MHz. The Al values
differ somewhat, so the number of turns to get a given inductance will
be a little higher for grade 6 than grade 2. You only need to confirm
that the number of turns required will actually fit on your T68-size
core.

For a given number of turns, the unloaded Q does peak at one frequency
but is still quite good on either side of that frequency. Unless you
have some real need to achieve the highest possible Q for a given
inductance at the frequency of interest, I wouldn't worry too much about
it. Wind the toroids, build the filter, and see how it works out!

--
Joe