"What was it?" asked Bob.
"I finally found that the water pipes were insulated from the street pipes, as they are in some houses, so that I really didn't have any ground at all, even though my ground wire was connected with a pipe in the bathroom. I might have been looking for the trouble yet if a friend of mine hadn't given me a tip what to look for."
By this time they had reached Bob's room, and Dr. Dale and Mr. Brandon inspected the boys' outfit with great interest.
"Pretty good for beginners, isn't it, Brandon?" said the minister at length, when they had gone over the thing at length and Bob had explained the way they had made the different units.
"I should say so," acquiesced the expert. "They've made up one of the neatest amateur jobs I've seen in a long time. Let's see how it sounds."
He and the doctor donned head phones, and Mr. Brandon manipulated the tuning coil and the crystal detector with a deftness that spoke of long experience. He showed the boys how they might get even clearer and louder tones than any they had yet obtained by adjusting the detector until the best possible contact was obtained with the crystal.
"You could hear better with a more elaborate set, of course," he said, "but you get mighty good results with what you've got. Of course, you're range is limited to less than two hundred miles with this set, and your tuning range is limited, too. But you've made a fine start, and with this as a foundation you can go on adding equipment, if you like, until you have a first class receiving station."
"Yes, and after we get a little more experience, we want to try our hand at sending, too," said Joe.
"Well, that's a more complicated undertaking," said Mr. Brandon. "But there's no reason why you shouldn't, if you are willing to go to the trouble to learn the international code and take an examination. You have to be able to receive ten words a minute, you know, to get a license."
"I suppose you're an expert both sending and receiving," said Bob.