“What?” shouted Brandon, leaping excitedly to his feet. “Do you really mean that? Tell me all about it.”
For the second time that evening Bob recounted the happenings of their eventful excursion, while the radio inspector listened intently, throwing in a question here and there. When Bob had finished he made no comment for a few minutes.
Then he took the copy of the code and examined it intently, jotting down phrases here and there in his own notebook.
“Well,” he said at length, “this looks to be a much bigger thing than I had supposed. Of course I heard of the robbery of the motor-truck, but I never for a moment connected that with this sending station we’ve been looking for. It seems fairly evident, though, that if we can lay our hands on the operators of the unauthorized sending outfit, we’ll also have the perpetrators of that hold-up. This is a case where we’ll have to think out every move before we act.”
“Just before you arrived I was considering the advisability of putting the matter into the hands of the police,” said Mr. Fennington. “What would you do?”
“Keep the whole thing to ourselves for the present,” said Mr. Brandon decisively. “I’ll send for a couple of good men to come up here and help me, and we’ll keep a watch on that cabin for a few days. If this thing got into the papers, it would put the crooks on their guard, and probably spoil our chances of catching them and getting back the loot. I’ve got a small but extremely efficient receiving and sending set in my car, and if any more code messages are sent out we’ll catch them.”
His confidence was contagious, and the boys felt almost as though the capture of the criminals had already been accomplished.
“What puzzles me, though,” remarked Mr. Fennington, “is how you knew that there was an unauthorized radio sending station in this neighborhood, Mr. Brandon. I should think it would be almost impossible to locate such a station, even approximately.”
“On the contrary,” replied Frank Brandon, “it is little more than a matter of routine. Probably any of these radio fiends here could explain the method as well as I can, but I’ll try to make it plain to you.
“There is a certain type of aerial that has what we call ‘directional’ properties, that is, when it is shifted around, the incoming signals will be loudest when this loop aerial, as it is called, is directly in line with the sending station. The receiving antenna is wound on a square frame, and when the signals are received at their maximum strength, we know that the frame is in a practically straight line with the sending station we’re after.”