I have two Zenith FM radios, an early 60's plastic table radio and a 1959 C845 (big table radio with great sound). Both bring in FM pretty well with a capacitor in a metal housing clamped to the power cord for an antenna. The cord is just a two conductor lamp cord.

My 1949 Marconi FM252 is recapped and repaired and received FM OK while out on the bench with a simple dipole antenna attached, but now that it is up on the special shelf I built to take a 40 lb brute of a table radio, FM is gone, even with an external antenna. Before I rig something outside for it, I would like to try a power cord antenna. An alignment would also be helpful, I'm sure, but first a good antenna.

Can anyone steer me towards a design? Is the length of the power cord critical? I suspect this system utilizes the whole house wiring as a big loop antenna?, but would like some more info.

The wire clamp on your Zeniths for FM is just a loose coupling to use the AC line cord as an antenna. You can basically do the same thing by wrapping the FM antenna wire around the AC cord a few turns.

:The wire clamp on your Zeniths for FM is just a loose coupling to use the AC line cord as an antenna. You can basically do the same thing by wrapping the FM antenna wire around the AC cord a few turns.
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Thanks, Warren. I will have to experiment, as I have two terminals on the Marconi, as well as a grnd screw.