A resonant antenna takes current better and current radiates. But when
the high current part of the antenna is in the loading coil it doesn't
radiate nearly as well as if the loading coil is connected a distance
from the feed point so the maximum current is in a straight wire. That's
presuming a single wire resonant as 1/4 wave so the opposite end is high
impedance and its low impedance at the feed point. It takes more coil at
the outer end than at the feed point to get resonance. A resonant
antenna is always easier to feed and a center fed half wave dipole or
end fed quarter wave presents impedances at resonance that match coax
pretty good.
73, Jerry, K0CQ
On 4/8/2011 6:42 PM, Richards wrote:
> Greetings Antenna Mavens --
>
> In my bailiwick, it is common for those working 160 m to use a long
> sloping wire with a particularly long loading coil. Many use a 70 foot
> straight wire to or from a 70 foot wrapped loading coil – sometimes
> mounted as a single sloper worked against a tower, or as a dipole.
> Some put the loading coil up close to the feed point, while others put
> the loading coil at the far end, like at the far ends of a dipole, or
> the bottom of the sloper. I have heretofore considered this a huge
> loading coil, and they tell me that it resonates well because of the
> length of the wire. I've always been skeptical of the real value of the
> loading coil, but they swear by these things.
>
> Would anything like this help in this case, considering the poster has
> such a relatively short backyard area. I'm interested in the answer,
> myself, because I have an even smaller backyard than he does, and would
> also like to work 160 on a better antenna that I have now.
>
> Any traction?
>
> ------------------
> Happy Trails.
> ======================= Richards / K8JHR =========================
>
> On 4/8/2011 3:52 PM, Steve Hunt wrote:
>> Irrespective of the matching problem, such a short dipole is going to
>> give you very significant losses in the feedline. If you could lengthen
>> the dipole to 200ft, TLW predicts the open-wire loss would be much more
>> acceptable at around 0.7dB.
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