Many thanks to SWLing Post contributor, Rolf, who writes:

I made a great discovery tuning using a second passive analog radio.

When I tune to Radio Caroline, for example, on my portable I can receive the signal okay. When I put the receiving radio on minimum then place it next to and couple it with the second radio, it is receiving a lot better!

Even stations I could hardly hear, now i can hear them!

Check out my short demonstration video:

Click here to view on YouTube.

That is fascinating, Rolf. Thank you for sharing. Indeed, this is one of the reasons why I try to maintain a good distance between radios when comparing them in reviews. In this case, though, you’re using coupling to your advantage!