Fig 3. Photographs and schematics of the single-tune circuit boards (CB1, left and CB2, center) and dual-tune circuit board (CB3, right) with and without loop-gap (LG) inductors.
Conventional BNC connectors (left and right) as well as a custom-made PTFE coaxial cable with low hydrogen content are shown (center). Values of variable capacitors are: CV1,3-9 = 0.3–3.5 pF, CV2,10,11 = 1.1–16 pF; fixed-value capacitors: CF1 = 1 pF, CF2 = 100 pF, CF3 = 6.8 pF, CF1 = 10 pF; inductors: L1,2 = 22 nH.