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

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.

If you can post the schematic and the operating frequency somewhere,
someone here may take a stab at suggesting an inductance.

Or wait and see if someone in Europe or with experience with European
parts gives you a response.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

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.

If you can post the schematic and the operating frequency somewhere,
someone here may take a stab at suggesting an inductance.


the schematic is 470K pdf, write me privately and I'll send it.
Thanks for help.

Francesco IZ8DWF

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

On 18 Jun, 17:02, wrote:
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

Neosid coil formers and cores have always been popular in Europe. They
are still made, but it can be difficult to buy them.

Leon

The following link will take you to some of the Denco (and other
manufacturer's) data sheets about the old coil formers and dust-cores.


http://vintageradio.me.uk/info/dencocoils.htm

Hope this helps

Derek.

In message
,
writes
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

--
Derek R. Smith.

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
=============================================
Purple coloured toroids are for example Ni-Zn ferrite type 4C65 made by
Philips.
For inductors used in frequency determining circuits (vfo), powder-iron
cores are normally used .

Ferrite for RF applications is usually applied in chokes , baluns, ununs.


Frank GM0CSZ / KN6WH