My expectations were in line with F6FLT and Smudge's
...however experiments show that induction IS happening.
What would you suggest to eliminate errors caused by capacitive coupling and coaxial cable imperfections ?
My idea for the latter is to insert a normal coax into a bendable but solid copper tubing, in order to make a very low-loss coax ( double shielded  ) ...and retest.
...but how to quantify and control the capacitive coupling?
There is surely a measurable, some pF capacitance between the shield of the coax and any one end of the secondary coil wire. I would suggest to form a parallel resonant circuit for 45.5 MHz with this capacitance by connecting two small RF toroidal coils as I indicate in your earlier drawing. The two coils should have resultant inductance appropiate for resonance with the capacitance at 45.5 MHz. If the created galvanic connection between the coax and the secondary is not wanted, then a some hundred pF (or higher value) capacitor could be connected in series with each coil to eliminate galvanic connection. Regarding the copper tubing, it is ok to shield the coax further on, alternatively a cheaper solution would be to wind a Alu foil bandage around the coax cable in a few layers. Self adhesive Alu tapes may also make fixing wire connections to such bandage a bit easier. Gyula
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Topic: Coaxial Cable Coil Induction (Read 4608 times)
