I had a RCA Radiola 15 for a number of years. I restored it and it plays. Its a tuned radio frequency device. It was one of the very first AC plug in radios. Two stages of RF amplification are within the radio. The RF signal is then high enough to get through the detector. It requires a long antenna. I likes to pick up WJM knoxville at night. Receivers today are all superhetrodyne. A short internal antenna will do with these.
I was at a yard sell last week and came across a Radiola III. They thought it was a metal detector. It is in good condition and I grabbed it. Its about 90 years old, cera1923. I plan to restore this one too. It ran on batteries. I will have to build a battery replacement pack. I not sure where to get the tubes. I may put FETs in the device and use a more modern tubes simply for aesthetics. The RCA radiola III is a super-regenative receiver. It has a gain knob that can be turned up until it oscillates. The original headphones were with the device. This one will be fun to play with. Its fun to work both with old (radios) and new (apps) technologies. http://www.angelfire.com/scifi2/zpt/images/radiola3and15.jpg Frank Znidarsic
