Anybody know anything about antique radios?

[radioian]

A fan of vintage valve radio sets here in the UK; my oldest set is a 1933 round EKCO AD65, and my newest set is a 1961 SABA FRIEBURG 125. I have about 12 sets here in the house, but have sold on about 40!

 

[pigface]

That big round thing by the speaker looks like it's the speaker electromagnet. It draws power from the plug — a helluva lot of power, which can be very dangerous if the parts are degraded.

The guy who fixed my radio told me the speaker had been replaced years before, probably to eliminate the need for the power-draining and heat-generating electromagnet.

Field coil loudspeakers (if that eveready is one, I'm not so sure) serve two purposes, and replacing one with a permanent-magnet loudspeaker can cause problems.
Field coils were used in powerful loudspeakers (that is anything over about 10 Watts) because the permanent magnets they had back then could be de-magnetised by a strong audio signal delivered to the loudspeaker's voice coil.

The field coil also served double duty as the series inductor for the power supply filter. An inductor has a high resistance to AC, low resistance to DC. It is necessary to protect the rectifier tube from too much AC ripple. If you eliminate a field coil speaker, you have to substitute a replacement inductor, or risk destroying the rectifier tube.

Re the loop antenna show in the link:
This will work, BUT it is a compromise. They are using a small physical antenna, and making up for its poorer performance with a fet amplifier, so the end result is a noisier reception, even though it might be as sensitive. Still, if you are stuck for space it might be the only possible solution. But the parts are so cheap, its not any loss if it doesnt work well, so worth trying.