On 5 sep, 14:56, ml wrote:
hi

Over the years, I've found it interesting and disturbing even
confusing, that there seems to be so much confusion regarding the
above.

Nothing gets a post responce, like the above topic and boy those
threads quickly grow to large numbers

I always read them trying to learn as well as books on the topics,
i don't pretend to have any formal engineering /scientific
knowledge just enjoy reading what i can

but i ponder why there seems to be so many opposing /contradicting
views on same subjects and topics and i am not referring to just
those here on the news groups

if i get x people in a room ask about baluns or chokes 1/2 say one
thing the other 1/2 say something else

dunno it's strange in all that confusion obviously we all pick
what we interpert and believe to be best but i hate when that happens

Hello ML,

Is it really opposing /contradicting or just different?

Most baluns (in antenna systems) are used to make sure that the
current in the antenna structure is far higher then the common mode
current in the feedline.
Common mode current = Icenter + Iscreen.

To say in other words: function of balun is to make sure that the feed
line does not take part in the radiation process.

Some issues that may affect the type and actual design of the balun:

1. "far higher" (how good it mist be) is not a hard figure and depends
on the application. Requirements for a field day will be different
then for an EMC measuring antenna in an anechoic chamber.

2. The behavior of the balun depends on the impedance levels (both
common mode and differential mode) on both balanced and unbalanced
side. A balun for a full wave dipole "receives" more voltage stress
than a dipole for a HW dipole (at same power level).

3. A balun can be narrow band and wide band (ferrite core baluns
[wide] versus resonating transmission line [narrow]).

4. Some baluns have the function to generate two opposite voltages
with respect to another point (even when the load is not fully
balanced [for example in electronic circuits]).

5. Financial issues may play a role (especially in mass volume
products). A balun on PCB is far cheaper than a coaxial one with
ferrite cores.

6. How much insertion / mismatch loss is allowed, what about power
handling?

Just by mentioning 6 points, you can imagine that a certain balun does
perform well in application A, but not in application B. A wrong type
of balun for a certain application may even make the situation worse
(while that balun is OK for another application).

Like Cecil, when 1:1 impedance is OK up to VHF, I prefer the current
choke balun (the one with the ferrite cores). If possible with low Q
factor for the common mode inductance.

For the upper UHF and SHF, performance of ferrite ceases and other
types (like shorted quarter wave sections or tapered lines) can be
used.

As there are many varieties, two poeple may say different things, but
they are both right.

Best regards,

Wim
PA3DJS
www.tetech.nl
the address is OK but don't forget to remove abc