“I suppose you use a tickler coil in the plate circuit, don’t you?” ventured Joe.
“No, in this set we use a variometer in the plate circuit instead,” said Thompson.
“Speaking of regenerative circuits, have you heard about Armstrong’s new invention?” asked Bob.
The operator shook his head. “Can’t say that I have,” he said. “It must be something very recent, isn’t it?”
“Yes, I believe it is,” said Bob. “I read about it the other day in one of the latest radio magazines.”
“Do you remember how it worked?” asked Thompson, eagerly. “I wish you’d tell me about it, if you do.”
“I’ll do my best,” promised Bob. “The main idea seems to be to make one tube do as much as three tubes did before. Armstrong found that the limit of amplification had been reached when the negative charge in the tube approaches the positive charge. By experimenting he found that it was possible to increase the negative charge temporarily, for something like one twenty-thousandth of a second, I think it was. This is far above the positive for that tiny fraction of a second, and yet the average negative charge is lower. It is this increase that makes the enormous amplification possible, and lets the operator discard two vacuum tubes.”
“Sounds good,” said Thompson. “Do you suppose you could draw me a rough sketch of the circuit?”
“Let’s have a pencil and some paper, and I’ll make a try at it,” said Bob. “I doped it out at the time, but likely I’ve forgotten it since then.”
Nevertheless, with the friendly aid of the eraser on the end of the pencil, he sketched a circuit that the experienced professional had no difficulty in understanding.