I have the following circuit on a breadboard connected to a RiGOL DG1022 function generator as the input voltage source (V1). (R1 is supposed to model the resistance of the function generator and is not part of the circuit itself).
The function generator is set to output a sine wave of 1 MHz and an amplitude of 5 Vpp. As can be seen from the picture, it is set for high impedance mode.
The two coupled inductors inductors are realized using two soda bottles with 20 windings of copper wire each. When I bring the soda bottles together, and measure the voltage of V1 using RIGOL DS2072 oscilloscope, I get the following measurement: . The Vpp shown in the oscilloscope is 4.36 (which is legit since the function generator is trying to output Vpp of 5 volts).
When I increase the distance between the soda bottles, the measured voltage ACROSS THE FUNCTION GENERATOR drops to 2.72 Vpp. As in the following picture:
I would like to know how come the function generator voltage drops when I increase the distance. I know that changing the distance changes the impedance of the coils, but how does it affect the voltage of the wave-generator? Is it because of its output impedance of the function generator (even though it is set to the High Z mode)? I tried changing the output impedance of the function generator but it still showed the same effect.