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Radio-Frequency Amplification From
the Ground Up
With Some Simple Details for Applying It to Your Present Receiver With Little Difficulty, and a Series of Six Graduated Circuits
By ARTHUR H. LYNCH
M
UGH of the trouble experienced by listeners-in is directly due to an exaggerated ambition for long distance. Many of them read descriptions of new forms of receivers for which great claims are made and they decide to have one — and have it immediately. As a rule, their knowledge of the set is confined to a few technical terms which they repeat in parrot-fashion to some harassed dealer who is just as much in the dark as they are. Not more than a few days ago, a youngster asked me to draw a diagram and tell him how to make a radio compass. In the course of the conversation that followed, he described his single-tube receiver, which had been assembled from units bought one at a time, after comparatively long periods of saving. He spoke of the purchase of his storage battery as a great event and prided himself on a pair of phones that cost eight dollars — and he wanted a radio compass, for he had read of the great work being done by the U. S. Navy at its compass stations. He had a notion that a
radio compass could be made in a few minutes by adding a loop or something to his outfit. He thought it would be a fine thing to carry around and locate stations that interfered with his receiving. He also had some very vague ideas about radio-frequency and super-regeneration and many other technical subjects of which he knew little more than the name, but he was anxious to try them all — at once.
And this lad is just like a great many others and they are not all youngsters. It is a mighty good thing for the person just being initiated into the vagaries of radio to be satisfied with a good single-tube, three-circuit, regenerative receiver until he has mastered it. It takes a lot of skill to get the best from a receiver of this type and vacuum-tube detectors themselves offer plenty of opportunity for experiment before the best working point is found. Two steps of audio-frequency amplification do not cause much additional difficulty and are helpful when you desire to use a loud-speaker. They add but little to the distance over which you can receive, however. Of course there are some
FIG. I
A single-stage, transformer-coupled, radio-frequency amplifier and vacuum-tube detector applied to a standard coil mounting. Various adaptations of this arrangement are possible