This is an early project for a tactical RX loop over all 40 meters HAM band. No need adjustable high voltage capacitor. Only need about 2 meters foam -75 ohms, vf:0,82- coax and a fixed 150 pF capacitor (ceramic type, low voltage -remember.. RX antenna only!).
Emergency style, simple and easy to make, but amazing performance. Try yourself!
This are some model draws:
And two photographs tunna-tin made style. 80 meters prototype:
20, 40 and 80 prototype: