I am building an AM Radio and I have constructed a tuner circuit. See below.
However, I cannot use this circuit, because even though in my calculations it works, I am not able to see the signal for the 570kHz band when it's connected to the oscilloscope. The 570kHz band will only show up if I drop my inductance down to about 250 uH. To me, this doesn't make sense and so I'm trying to track down the culprit.
After finding the band 570kHz, I measured the capcitor and found that my capacitor was set to about 234 pF.
Thinking this was odd, I put my LCR meter to the inputs of the oscilloscope and found that it has an inductance that fluctuates from 1000mH to 2000mH.
Is my oscilloscope affecting my tuning circuit, or is there parasitic capacitance somewhere in my circuit that is affecting it?
I want to be able to use the circuit I've described here so I can get a better band pass filter (I want high L and low C).
Details: - the oscilloscope I'm using is an Iwatsu SS-5702 oscilloscope -- quite an old model - my inductor is hand made and measure to be 1960uH - my antenna is just a piece of wire - I'm using a spring board to connect the parts