Guy Olinger K2AV wrote:
> Counting FCP segments 1 through 5. 33 feet per segment. Directions
> used are for illustration only.
>
> 1: center to 33 feet east
> 2: 33 feet east back to center
> 3: center to 33 feet west
> 4: 33 feet west back to center
> 5: center to 33 feet east and end insulator.
Your analysis IMHO doesn't take into account coupling between
the two conductors in the open wire line. I would characterize
the above as a 33 foot radial in series with two 33 foot
shorted stubs. A 33 foot shorted stub made of 600 ohm line
is equivalent to about 20 microhenries of inductance.
Two of those add up to 40 microhenries. This is close to the
55 microhenry loading coil you mentioned. Using a shorted
stub of OWL to implement an inductor is an implementation
decision. It seems less lossy because it doesn't get hot;
the heat is spread out over a large area. But you still have
the copper losses of a considerable length of wire which
add up to a similar amount of loss that a big coil would have.
You're probably right that it's cheaper than a coil, at least
if you buy it new. Again, nothing wrong with doing this;
I'm sure it works, but there is nothing magic going on here.
It sounds like a nice ham-proof implementation of short elevated
radials, which can be tricky to install the usual way.
I don't see how any of this improves bandwidth except
to the extent it adds loss to the system. There is a known
relationship between antenna size, bandwidth and efficiency.
Networks on the ground don't fundamentally affect this.
Replacing an inductor with a shorted stub is always detrimental
to bandwidth because the inductance of the shorted stub is
proportional to frequency, instead of constant like the
inductor.
Rick N6RK
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