OCF: Proprer type of balun (transformer)
Michael Coslo wrote:
I've always wondered, when people take these antennas that are likely to
have feedline radiation, and try as they may to stop it, isn't it likely
that they are making the antenna not work as well as it might have if we
just left the feedline radiate as it would? You might be taking away a
major part of the antenna performance?
I have to expect that a radiating feedline would have to be a pretty
inconsistent sort of antenna from one installation to another.
- 73 de Mike N3LI -
Absolutely. A radiating feedline is part of the antenna, as is the
entire path to the Earth along the outside of the rig, through the mains
power system or whatever other path it can take. So two people thinking
they have the same "antenna" can really have very different radiating
systems.
Sometimes the radiation from the feedline, mains wiring, and stuff in
the shack can be beneficial -- it might, for instance, fill in deep
nulls in the main antenna's pattern and result in a spectacular signal
strength improvement in particular directions. On the other hand, it can
cause lots of problems. For example, when I was testing an OCF dipole a
while back, on one band my electronic keyer would lock up after the
first "dit" due to RF in the shack and on all the station connecting
wires. And having the power wiring be part of your antenna system can
lead to trouble with telephone, TV, and other kinds of interference. But
then you might get lucky and get away with it.
Probably because of the same personality quirk that led me to become an
engineer, I prefer to be able to predict and understand how my antenna
system will work, and design it to work as I want, rather than making it
a crap shoot. But that's surely not the only, or necessarily the best,
way to get on the air and talk to people.
Roy Lewallen, W7EL
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