On Thu,4/7/2016 8:28 AM, TexasRF--- via TowerTalk wrote:
Why would you not just solder the balun flying leads to a PL259 connector
for connection to the dipole connector and be done with it?
First, the word "balun" is used to describe almost a dozen very
different things that I can think of. It's a contraction of "balanced to
unbalanced," implying a conversion.
Second, it is ALWAYS good practice to use a ferrite COMMON MODE CHOKE at
the feedpoint of ANY antenna that does not intentionally USE the
feedline as part of the antenna. The reason is to PREVENT the feedline
from being part of the antenna, which in turn prevents the feedline from
picking up signals and coupling them to the antenna. Those signals
picked up on the antenna may be noise, or from some direction other than
that favored by the antenna.
Third, the best common mode choke for the HF bands is one formed by
winding multiple turns of the feedline through one or more ferrite
cores. Simply clamping a lot of cores onto the coax WILL NOT WORK WELL.
Neither will a simple coil of coax. See the references below to
understand why.
I first did research common mode chokes in 2004-5, and published the
results as a technical paper for the Audio Engineering Society. The
emphasis there was preventing RFI to audio systems. After moving to W6
in 2006, I continued my research and published the first version of
http://k9yc.com/RFI-Ham.pdf in 2007. There have been well over a million
downloads, and some key elements of the material has been added to the
ARRL Handbook. Slides from a talk I've done for several hamfests and
clubs are at http://k9yc.com/CoaxChokesPPT.pdf
73, Jim K9YC
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