1) The operation of any CMC, current balun, true balun, or..... does not
depend on voltage. It's all about current. Voltage alone does not, I
repeat, not induce magnetic current in the ferrite toroids! Only current,
flowing current (that's a double whatever), produces magnetic currents in
the toroids. Capacitance is all about voltage and voltage is responsible
for aligning the polarization vector in dielectrics. Current alone can not
accomplish that. Inductance (magnetic currents in the ferrite material) is
all about current and flowing charges are responsible for producing the
magnetic currents in the toroids. Voltage alone can not accomplish that.
Visit Lenz's Law for a clearer explanation:
's_law
2) A bifilar wound toroidal CMC is a bilateral device. From a circuit
aspect, both ends are identical. In place between the output of the
matching network and the open wire feeders, it converts CM to DM. This is
the function and only function of a true balun - NOT a transformer. One
could turn the CMC completely around - swap port for port - and the result
would be identical.
Dave - W?LEV
On Mon, Jan 18, 2021 at 3:22 PM Manfred Mornhinweg <manfred@...>
wrote:
Jeff,
Could you please explain what you mean by "end-to-end"? There are four
"ends"
in the CMC and I'm trying to understand which ends you are referencing --
input-pair to output-pair, or between in and out of one wire, or...?
I mean, voltage applied to those 12 turns. Short the input pair to make
one connection, short the output pair to make the other connection, apply
the voltage between those two points.
In a "textbook" antenna installation, such as a perfectly symmetrical
horizontal dipole, symmetrically over ground, with the feedline coming down
straight and vertical, no other objects nearby, and fed from an unbalanced,
perfectly grounded transmitter, with the dipole impedance and cable
impedance being identical and the CMC's impedance being infinite, the
voltage appearing end-to-end on a CMC used as balun is one half of the
transmitter's output voltage. In a typical practical installation it's
usually lower, but with some bad luck it could also be higher.
Also, why 170V RMS?
Because the applied voltage defines the flux density in the core, along
with frequency, number of turns, and core dimensions. And for the core size
(FT-240) and turns number (12) considered here, 170V at 1.8MHz results in a
flux density of about 11mT, which for this particular core material (31)
results in a volumetric loss of roughly 300mW per cm?, which I somewhat
arbitrarily defined as a reasonable value for intermittent service.
And I made the calculations at 1.8MHz because it's the worst case. On
higher frequencies the loss gets lower.
Manfred
--
*Dave - W?LEV*
*Just Let Darwin Work*
