> I have a bunch of old antique and near-antique tube radios that I would > like to hook up to my outdoor antennas. What impedance should I assume > for the antenna terminals so I can build matching/isolating transformers > to attach to me coax lead-ins? I know it will probably vary with the > radio, but what is a good ballpark impedance value to work with?
Most were set to work with a long wire or multi-turn untuned loop, so I'd guess 450 ohms (9:1) would work well. That would be my starting place... Be careful if you use a separate speaker. Some of the old radios used a coil and steel core for the speaker magnet which doubled as the choke in the power supply. These can usually be recognized by a four-pin speaker connection. I haven't worked with one of these for many years. They always were fun. When I was a kid I fixed a 1940-vintage receiver. I turned it on and my mother happened to be in the room. When it came on, Franklin Roosevelt was heard giving a speech. It was in the late 50's and some station was rebraodcasting it for some reason. It certainly freaked out my mother when she looked at the radio and heard that! Couldn't have planned a better joke if I'd tried. Craig Healy Providence, RI _______________________________________________ IRCA mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: [email protected]
