The time to make some further improvements to the Hartley transmitter has come. I wanted a more stable tone when the wind blows. It's Fall at the time of writing this post ... so having a warm tube on the desk, to make some good QSO with my friends, is just perfect on this part of the year.
The antenna link made by rigid Copper wire has been replaced by two turns of coaxial cable, wound right upon the main coil. The braid is left open on one side, and grounded on the other. The central conductor is the usual link to the antenna.
It's important with a Hartley having a center tapped coil, to place the link right in this position: the ground connection of the tap brings the electric potential of the turns, here, the minimum, therefore making also minimum any stray capacitive coupling to anything around.
By placing the antenna link here, plus electrostatically shielding it, by the grounded coax cable braid, the tone quality is now much better and the frequency sensitivity to a windy weather, reduced.
And here, the result: the transmitter, loaded into the antenna, normally waving in the air ...