The German Navy VLF antenna at Rhauderfehn (Ramsloh)
23.4 kHz is multiple tuned. It comprises eight
325.5 metre umbrella top loaded antennas.
Each antenna is separately fed, and the 8 elements
of the antenna array are coupled through radiation.
Rr= 1.9 ohm; Rg= 0.15 ohm; Ras= 2.25 ohm; eta= 87%.
73 from Vaino, OH2LX
At 17:47 28.8.1999 +1200,
Rik Strobbe wrote:
But what to do with the 'loss resistance' (RL) in the real world ?
Assume a simple model where both tuned sections share the same
ground-system. In that case RL would be in series with R and this would
mean that a double tuned vertical would not only quadruple the radiation
resistance but also the loss resistance, resulting in an unchanged ratio
between radiation resistance and loss resistance.
Bob ZL2CA wrote:>
Which is basically what I meant in my previous comments about
"transformer action" from the division of current between multiple tuned
vertical feeds. It is similar to a folded dipole transformation.
Overall, multiple tuned verticals are still a similar antenna structure
from the point of view of "looking back at it from some distance away".
Multiple tuned vertical parts are an "impedance transformation trick"
but do very little, if anything, for the net radiation resistance of the
whole antenna. Where some advantages are likely is in the multiple
grounds.
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