Here's a whole slew of Atwater Kent schematics redrawn to modern standards. Take a look at the model 20.
http://www.atwaterkent.info/TechData...wingIndex.html
For your indoor antenna try connecting the radio's ground to the third wire ground(green) of your homes AC wiring, which in theory goes to earth ground at your service entrance. Then try a short length(10-15 feet of whatever wire) stretched out across the basement floor. That short wire should pick up whatever radio signals are radiating off your homes AC wiring. I have very good reception from local stations using this method, but I also hear every appliance in the house turn on and off, as well as well as all the crappy wall wart switching power supplies that most every modern day electronic devise use. Nothing can compare to a 50-100 foot wire strung up outside far away from other electrical interference. I have about 50 foot going from my shop to a tree with a grounded shield coax(75 ohm) leading all the way to my basement. Ideally you want to earth ground the coax shield only where the antenna enters your home, then you can use the shield as the radio ground at the other end of the coax. Yes there are loses using coax for lead in but they are negligible relative to the overall clean signal you receive.