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Where only one vacuum tube is used for producing both frequencies you need only a regenerative, or feed-back receptor; then you can tune the aerial wire system to the incoming waves and tune the closed circuit of the secondary coil so that it will be out of step with the former by 1,000 oscillations per second, more or less, the exact number does not matter in the least.
This is the simplest type of heterodyne receptor and it will receive periodic waves from spark telegraph transmitters or continuous waves from an arc or vacuum tube telegraph transmitter. In this type of receptor the detector tube itself is made to set up the heterodyne oscillations which interfere with those that are produced by the incoming waves that are a little out of tune with it.
With a long wave autodyne, or self-heterodyne receptor, as this type is called, and a two-step audio-frequency amplifier you can clearly hear many of the cableless stations of Europe and others that send out long waves. For receiving long wave stations, however, you must have a long aerial a single wire 200 or more feet in length will do and the higher it is the louder will be the signals.
"The ... the justice," said Derec tearfully, "didn't name it in court, because it would have to be published. But he's set your bond at fifty million credits! Nobody could raise that for you, Bron! And with the reason for it what it is, you'll never be able to get it reduced." "But anybody who looks at the plans of the receptor will know it can't make deathrays!" protested Hoddan blankly.
If you have a short-wave set and plan to receive intermediate waves with it then loading coils and fixed condensers shunted around them affords you the way to do it, but if you prefer to buy a new receptor then the better way is to get one with bank-wound coils and variable condensers; this latter way preserves the electrical balance of the oscillation circuits better, the electrical losses are less and the tuning easier and sharper.
The easiest way to get a clear conception of how a wireless transmitter sends out electric waves and how a wireless receptor receives them is to take each one separately and follow: in the case of the transmitter, the transformation of the low voltage direct, or alternating current into high potential alternating currents; then find out how these charge the condenser, how this is discharged by the spark gap and sets up high-frequency currents in the oscillation circuits; then in the case of the receptor, to follow the high frequency currents that are set up in the aerial wire and learn how they are transformed into oscillations of lower potential when they have a larger current strength, how these are converted into intermittent direct currents by the detector and which then flow into and operate the telephone receiver.
To produce these beats a receptor can use: a single vacuum tube for setting up oscillations of both frequencies when it is called an autodyne, or self-heterodyne receptor, or a separate vacuum tube for setting up the oscillations for the second circuit when it is called a heterodyne receptor. The Autodyne, or Self-Heterodyne Receiving Set.
The easiest way to get a clear conception of how a wireless transmitter sends out electric waves and how a wireless receptor receives them is to take each one separately and follow: in the case of the transmitter, the transformation of the low voltage direct, or alternating current into high potential alternating currents; then find out how these charge the condenser, how this is discharged by the spark gap and sets up high-frequency currents in the oscillation circuits; then in the case of the receptor, to follow the high frequency currents that are set up in the aerial wire and learn how they are transformed into oscillations of lower potential when they have a larger current strength, how these are converted into intermittent direct currents by the detector and which then flow into and operate the telephone receiver.
According to Sherrington, a given receptor has a low threshold for only one, its own specific stimulus, and a high threshold for all others; that is, the doors that guard the nerve-paths to the brain are opened only when the proper password is received.
The receptor for wireless telegraphy and telephony is the same and may include either a crystal detector or a vacuum tube detector, as will be explained presently. The Easiest Way to Start.
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