On Sun, 18 Jan 2009 12:35:01 -0800 (PST), JIMMIE
wrote:

K3MT had used them in 2M project so for the time being I will let it
go at that for now. Iam concerned about the cores saturating at that
power level but I doubt if there is a lot of info on it. When I get
off the road in a couple of weeks I will try hooking a couple of them
back to back to a dummy load, putting 10 watts in and seeing what
happens.

The web.

Jimmie

Hi Jimmie,

Last things first, you should Google in "Groups," specifically this
group. This isn't a guarantee, but at least you will land in a thread
where discussion will reveal flaws where they exist.

For a core to saturate reveals a misunderstanding of how the BalUn
works (it goes to the same correspondents who speak of "turns ratio").

The most effective BalUn provides a high common mode reactance or
resistance to current. Hence current in that mode will be low. With
low current into a high resistance you have low power dissipation.
Core saturation never becomes a problem, and is a distinctly separate
issue - although solved through the same mechanism.

The most effective BalUn adds absolutely no differential mode
reactance or resistance. Again, where there is high current and no
resistance, there is no power dissipation and zero core saturation
(for the same reasons, but through different mechanisms).

Practical BalUns have some residual reactances and resistances that
they add to the transmission circuit. A Ruthroff BalUn design even
purposely introduces this to its own limitation (and no advantage over
other designs). The Ruthroff design invites core saturation. A
Guanella BalUn seeks to be the most effective design to its advantage
over the Ruthroff. The Guanella design suppresses core saturation.
There are limitations, of course.

You can still flame out a Guanella if the core reactance/resistance is
under designed, or your load is unbalanced and not suited to the
transformation ratio. This can be aided through choking the input to
the BalUn (which serves as a choke, too, for controlled loads).

The back-to-back test is useful. Take one BalUn between a finger and
thumb and count to 10. If you don't raise a welt, then they probably
are not too lossy.

73's
Richard Clark, KB7QHC