Jim,
I've seen experimental data for a Guanella current balun, wound on a #43
material ferrite toroid with a bifilar winding, which shows the
efficiency as 97% (0.12dB loss) when working into its design impedance.
I'm puzzled trying to reconcile that data with your view that:
"When used in a transformer (voltage) balun, or in a choke wound with
parallel wire line, a core
with high losses (#43, #31, #77) will convert much of the transmitter
power into heat. The result
are 1) high losses (that is, several dB of the transmitter output is
lost in the balun); 2) balun performance
may degrade due to heating; 3) the balun may overheat; 4) the balun (or
the line) may
fail due to overheating (that is, the line may melt and either deform or
short, the ferrite may crack)."
Several dB of the transmitter output lost in the balun seems an awful
lot. If true, I don't see how any of the bifilar-wound current baluns
from the more reputable manufacturers could survive?
Steve G3TXQ
Jim Brown wrote:
> The primary problem is that there is a
> LOT of leakage flux from the differential field in virtually any bifilar
> winding. Not a problem on receive, but enough to cause SERIOUS heating on
> transmit.
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