Ron D'Eau Claire wrote:
needed to produce a balanced "feed" is a length of transmission line (1/4
wave or so) and a balanced load. If you have those things, it doesn't matter
Note that this is "approximately", not "at least". Ignoring losses, a
half wave would be ineffective.
whether the output from the rig is "single ended" or "balanced", the
currents at the balanced load, such as the center of a dipole, will be
balanced.
All a "balun" does is wind up that feed line in a smaller, tidier package so
A [1:1 current] balun does rather more than that. Firstly, the coiling
increases the inductance, so ignoring mutual capacitance changes and
that the inductance is behaving in a lumped way, L/C will increase and
therefore the common mode characteristic impedance will be much more
than the 620 or so ohms of a single wire feeder in free space.
Secondly, the radiation resistance will be much less than the 35 or so
ohms of a quarter wave of feeder in common mode, so it won't be
distorting the radiation pattern or picking up local noise.
The core material may be lossy, which also means that the common mode
signal will be dissipated as heat, which would only really happen for
the cable length if it were buried in the ground.
The un-importance of balance is shown in popular antennas like the G5RV,
The G5RV *is* balanced at the radio side input to the ladder line.
One important issue to remember is that a passive device is *not* a lossless
device. Passive devices, like baluns, all have losses.
They also have finite inductance, etc., so it is true that the real
world is more complicated than an ideal balun.
--
David Woolley
Emails are not formal business letters, whatever businesses may want.
RFC1855 says there should be an address here, but, in a world of spam,
that is no longer good advice, as archive address hiding may not work.
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