On 18 Giu, 17:37, Tim Wescott wrote:
wrote:
Hello,
in an old VFO project that I'd like to duplicate (seems easy and
stable enough for me), the inductors (2) are specified as a number of
turns on a 5mm former with
"purple core". Now I know what a 5mm former might be, but I surely
don't have any idea what a purple core is and how to recognize it on
my parts department :-)
Any info is appreciated, thanks in advance.

Francesco IZ8DWF

Some company in Europe that was popular with amateurs made ferrite or
iron-powder cores and color coded the mixes. Purple doesn't match the
color codes for Micro-Metals cores that are available in the US, so it's
not one of theirs (or it's an obscure one).

You may be able to figure out the inductance, and make the inductor some
other way. This takes away some of the 'easy', but it's at least a method.


Well, actually the inductances should be approximately 76 nH and 9.2
uH according to the frequency range of the VFO. But not having a
reliable method to determine cores characteristics from the ones found
on the parts box, I'd rather identify the good cores in some other
manner.
The long way will be just winding some (random?) number of turns on
random cores and see where it goes to oscillate, if oscillating at
all :-) But it's true, it's not as easy as before, and still wouldn't
tell me if the selected core is well suited for the frequency range
I'm interested in.

Francesco IZ8DWF