Huseyin:
What you are looking for are FT-37-43 and FT-50-43 cores.
These are not powdered metal cores; they are ferrite cores.
The red, yellow, and white cores are powdered iron; they work
ok in BPF filters and such, but are not recommended for broad-band
amplifiers.
I don't know offhand of a good source for you but you can
use FT-37-61 and FT-50-61 binocular cores. They are
found in the old 300/75 ohm splitter units used in TV antenna
lines to feed the 75 ohm input to the TV.
There are ferrite cores in computer power supplies also, but these
are usually of the wrong material and will not work well...but they
may work (usually they don't above 160m).
Consult on-line sources for winding data, such as that of W8DIZ.
The type 61 cores will take a few more turns than the 37 type cores
for the same inductance. They have the advantage of not saturating at
lower frequencies. I presume you can find some European sources for the type 37 cores;
that should work.
Hope this helps.
john
AD5YE
