Hi Guys,
Results of the build and test were that the 7Mhz HPF worked very well with
the "6" grade cores, but the 20Mhz LPF was crap (it used #6 as well). It
started to roll off at 20Mhz as expected, dropped smoothly to -10dB by the
time it got to 40Mhz, then stayed at 10dB at all frequencies above 40Mhz.
I suppose the core should be a grade #10 or #12 instead of #6? or perhaps
just a normal air core?
JEFF


"Jeff" wrote in message
...
Thanks for all the suggestions. Ive got some Amidon T68-6 toroids to wind
up, and will test the completed filter on a spectrum analyser next week.
JEFF

"Jeff" wrote in message
...
Hi,
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?
Thanks,
JEFF

"Jeff" wrote in message
...
Hi Guys,
Results of the build and test were that the 7Mhz HPF worked very well with
the "6" grade cores, but the 20Mhz LPF was crap (it used #6 as well). It
started to roll off at 20Mhz as expected, dropped smoothly to -10dB by the
time it got to 40Mhz, then stayed at 10dB at all frequencies above 40Mhz.
I suppose the core should be a grade #10 or #12 instead of #6? or perhaps
just a normal air core?
JEFF

Then you haven't built the filter that you designed. The choice of core
material will not affect the blow-by. If you measured the inductors at a low
frequency, I would be pretty certain that you have way too much inductance
at 20-40 MHz.

W4ZCB