I like listen to shortwave with my PL-380. I find that clipping the Sony wind-up antenna (that came with my 7600GR) to the PL-380 whip produces much more signal strength, and allows ETM to find many more stations.
This works fine when listening though the speaker, but when I listen through headphones, almost all of the signal is canceled out, and mostly what I hear is noise. It seems like the headphone cable is acting like an out of phase antenna, and canceling out the desired signal. I tried three sets of headphones with similar results. This even happens with earbuds that have only a three foot cord, but to a lesser extent.
Does anybody have an idea what is going on and why? What is the solution? Would an audio isolator (normally used for ground loops) help?