>
>Hi Larry...could you please help me understand what is meant by separate
>windings? I have wound a few ununs for beverages using the design details
>in ON4UN's and Maxwell's books. They were what I thought we standard
>winding techniques??? Does 'separate windings' mean that they are not
>trifilar or quadrifilar, but more like a power transformer with one part of
>the
>core supporting the primary and a separate part supporting the secondary?
>
>Thanks for your help.
>
>73, Tom
>W4iU
>(ex-WB4iUX)
>
>skelttom@gateway.com
Yup, you got it Tom. The old standard bifilar/trifilar windings have little
or no isolation between the primary and secondary. Even worse they are
usually connected as an autotransformer. With the primary and secondary
physically seperated by distance on the core, there is only a picofarad or
so of capacitance between them and so the only coupling is magnetic. This
pretty much eliminates the common mode problem that W8JI described at
length and I experienced in practice. The problem with this approach is
that the requirements for the core are very much more demanding. The
transformer I used that Earl described is not one I would actually have
recommended. It happened that those parts were on the bench and I just
threw them together to see what would happen. Now, I can say that it does
work, but I'm going to persue a more efficient design. Probably the
binocular type of transformer that W8JI suggested is what I will wind up
with, but I want to try a few more things before I commit to anything. At
least for now, the design that Earl mentioned is useable and uses real
common cores.
73,
Larry - W7IUV
w7iuv@axtek.com
www.axtek.com/w7iuv
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