[Elecraft] Building a power supply

[Julian (G4ILO)]

I'm just about getting round to building the power supply for my K2 into
the EC2 enclosure I bought a long time ago, when I discovered that the
transformer I was thinking of using is a few millimetres too tall. This
transformer has a single output winding which measures about 17V, which
would have been fine as I'm going to be using a bridge rectifier.

I'm looking at a toroidal transformer to fit into the EC2 case but I'm not
quite sure what I need, as the ones I can buy all have *twin* secondary
windings. Should I get one described as 2 x 9V and connect the two
secondaries in series? Looking on the web for guidance the only power
supply circuit diagram I found showed two secondaries connected in parallel
which seems to me (perhaps wrongly) as not the best thing to do. If the
windings weren't exactly matched you'd get current flowing from one into
the other, wouldn't you? If it is possible to use paralleled secondaries,
can I go for a current rating half what I want?

Also, is the magnetic field greater or less with a toroidal transformer?
The VFO of the FT-817 I had used to "warble" when sat on top of its power
supply, because of this.

The transformer supplier's web page is at
http://www.antrimtransformers.com/80VA.htm.

Thanks in advance for any help.
--
Julian, G4ILO. (K2 #392)
Homepage: http://www.qsl.net/g4ilo