I was able to pick several radio stations. I fixed the variable capacitor so that I can only hear the 1230 kHz station which I identified from the FCC call letter. I connected the antenna directly to my oscilloscope and obtained the following FFT:
How is it possible that the largest peak was not attenuated while small peaks surrounding the station I hear were attenuated even though I can't hear the largest peak frequency? and why is the voltage increased?