[TowerTalk] Re: Baluns
Tue, 3 Feb 1998 14:37:35 EST
I fear that we are making this thread more complex than it has to be.
A "Balun" (Balanced) (Unbalanced) is a device to adapt a balanced feedpoint
(tee match, omega match, dipole, etc) to an unbalanced coaxial transmission
line. In its most basic terminogy, it is the point at which the antenna ends
and the feedline begins. When constructed properly, a coax choke doest this
very effectively. I have one on every dipole and sloper I put up.
If you must perform an impedance transformation (i.e. KLM antennas with log
periodic elements) you need a transformer and a balun, which may be inside the
same physical device. Again, this can be done with coax for monoband antennas.
When you introduce ferrite to RF, you generate heat. In time, the heat can
change the properties of the ferrite. Impurities in the ferrite can also lead
to potential failure points. Sometimes you cannot avoid ferrite devices. Some
are very reliable, others are marginal.
To keep it simple, I use coax whenever possible. It would be nice to summarize
the reliability experiences with ferrite devices reported in this thread to
help us select the appropriate one for our applications.
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