Hi Roelof,
Another interesting information which is new for me. Thank you. I think
many of us have learned a bit from the topic.
I thought about using super glue to fix the winding on the core.
Or is this not to be recommended for some reason?.
I will use a T50-6 then. This will take a few days until i have it on
hand, unfortunately.
73, Stefan
Am 06.07.2012 09:39, schrieb Roelof Bakker:
Hello Stefan,
A FT-37-43 ferrite toroid is not suitable for a VFO as you found.
Powdered iron cores from Amidon are much better in this regard.
From the common available parts -6 material has the lowest temperature
coefficient,
-7 is slightly better:
T-50-2: 95 ppm/C
T-50-6: 35 ppm/C
T-50-7: 30 ppm/C
The temperature coefficient does not vary with the size of the toroid.
There are tricks to achieve mechanical stable windings on a Toroid.
One is to wind it as tight as you can and than place the coil in
boiling water for 10 minutes.
This removes the mechanical stress and the winding settles down.
73,
Roelof, pa0rdt
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