Actually a good example of this is the inverted vee. Where you
deliberately add a lot of sag :-) This tends to lower the feed point
impedance of the antenna. One thing to realize is that the resonant
point is changing because the wire is also getting longer as it sags.
On 12/30/2010 8:25 AM, Tod - ID wrote:
> Roger, K8RI, commented on the tension required to install a sloper antenna
> so that it had little or no 'sag' as it went from top to bottom.
> That caused me to contemplate the 'requirement' that all elements of slopers
> and dipoles must be in a single plane -- essentially a straight line in a
> single plane in three-space.
> Since we have a number of skilled EZNEC model makers on this reflector,
> perhaps one of them could do a small amount of modeling and help us
> understand just how much of a penalty we pay when our antennas 'sag' from
> end to end?
> I certainly hope this is one of those things that can easily be demonstrated
> to be very necessary. I have read with interest and watched with even more
> interest as folks have invested much time and treasure seeking to achieve
> the magic single plane state. If we had an idea of the penalty paid for
> failing to meet the ideal situation, it might allow us to make a
> knowledgeable decision on just how much time, energy and money should be
> devoted to achieving that state.
> As someone who is quite lazy and lets my wire antennas sag in a relaxed way
> by using only sufficient tension to keep the elements 'sort of in the same
> plane",[by no means do they really occupy space in a single plane] I am
> curious to know just how much of a catenary curve is tolerable -- or at
> have an idea of the rate of change of radiated energy from the antenna as a
> function of the departure from a straight line in a single plane.
> Tod, K0TO
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