[TowerTalk] "75-Meter Dipole Stretcher"

[Paul Christensen]

">Besides the loss problem you mentioned, a more fundamental problem is that a half wavelength line is only a half wavelength at one frequency, presumably the center of the band.  As you tune away from that frequency, the 1/2 wave line is no longer just an attenuator as you report, but it acts to reduce the bandwidth of the system. The more multiples of a 1/2 wave, the more reduction."

Rick,

Very true.  In some fairness to the author, he did set the 1/2-wave section length based on the lower frequency where the correction occurs, as the antenna is cut for the upper frequency where it's resonant.  

>"What I have been doing for a long time is to instead locate a capacitor at the feedpoint with the normally closed contacts of a relay across it."

That's the elegant solution if one wants to pass DC power on the line.   However, just using an RG-11 variant of cable pretty much solves the problems with reasonable efficiency and all the switching components can remain at ground level for easy servicing.

Paul, W9AC