Letters of a Radio-Engineer to His Son

You are interested in radio-telephony and want me to explain it to you. I'll do so in the shortest and easiest way which I can devise. The explanation will be the simplest which...

You have learned that the simplest group which can be formed by protons and electrons is one proton and one electron chasing each other around in a fast game. This group is call...

When I was a boy we used to make our own batteries for our experiments. That was before storage batteries became as widely used as they are to-day when everybody has one in the...

You will need several batteries when you come to set up your radio receiver but you won't use such clumsy affairs as the gravity cell which I described in my last letter. Some o...

I was pleased to get your letter and its questions. Yes, a proton is a speck of electricity of the kind we call positive and an electron is of the kind we call negative. You mig...

In my last letter I told how electrons are boiled out of a heated filament. The hotter the filament the more electrons are emitted each second. If the temperature is kept steady...

If we are to talk about the audion and how its grid controls the current in the plate circuit we must know something of how to measure currents. An electric current is a stream...

I trust you have a fairly good idea that an ampere means a stream of electrons at a certain definite rate and hence that a current of say 3 amperes means a stream with three tim...

Although there is much in Letters 7 and 8 which it is well to learn and to think about, there are only three of the ideas which you must have firmly grasped to get the most out...

In the last letter we learned of an alternating e. m. f. The way of producing it, which I described, is very crude and I want to tell how to make the audion develop an alternati...

Let's look again at the coils of Fig. 28 which we studied in the last letter. I have reproduced them here so you won't have to turn back. When electrons start from _a_ towards _...

In the last letter I didn't stop to draw you a picture of the action of the audion oscillator which I described. I am going to do it now and you are to imagine me as using two p...

audion oscillator. It was the condenser and inductance which you studied in connection with Fig. 36. That's what determines the frequency and also what makes the oscillations. A...

In the last letter we got far enough to sketch, in Fig. 54, a radio transmitting station and a receiving station. We should never, however, use just this combination because the...

An oscillating audion at the transmitting station produces an effect on the plate current of the detector audion at the receiving station. There is impressed upon the grid of th...

The radio-telephone does not transmit the human voice. It reproduces near the ears of the listener similar motions of the air molecules and hence causes in the ears of the liste...

You remember the audion characteristics which I used in Figs. 55, 56 and 57 of Letter 14 to show you how an incoming signal will affect the current in the plate circuit. Look ag...

There is one way of making an audion even more efficient as a detector than the method described in the last letter. And that is to make it talk to itself.

In our use of the audion we form three circuits. The first or A-circuit includes the filament. The B-circuit includes the part of the tube between filament and plate. The C-circ...

In an earlier letter when we first introduced a telephone receiver into a circuit I told you something of how it operates. I want now to tell why and also of some other importan...

In this letter I want to tell you how to experiment with radio apparatus. The first rule is this: Start with a simple circuit, never add anything to it until you know just why y...

0.10 103 169 179 0.20 146 238 253 0.40 207 337 358 0.85 300 490 515 1.80 400 700 760 2.00 420 750 800 4.00 600 1080 1130 5.00 660 1200 1260 10.00 900 1700 1790 30.00 1600 2900 3100

0.10 169 225 240 0.16 210 285 305 0.20 240 320 340 0.25 270 355 380 0.40 340 450 480 0.60 420 550 590 0.80 480 630 680 1.20 585 775 840 1.80 720 950 1020 3.00 930 1220 1320 5.00...

Inductance in Number Length Feet of wire mil-henries. of turns. in inches. required. 0.10 25 0.46 25 0.16 34 0.63 36 0.20 39 0.72 42 0.25 44 0.81 49 0.40 58 1.07 63 0.60 75 1.38...

2.00 120 2.22 160 3.00 158 2.93 215 4.00 194 3.58 265 5.00 228 4.22 310 8.00 324 6.00 450 10.00 384 7.10 530 12.00 450 8.30 625

To transmit speech by radio three operations are necessary. First, there must be generated a high-frequency alternating current; second, this current must be modulated, that is,...

In the matter of receiving I have already covered all the important principles. There is one more system, however, which you will need to know. This is spoken of either as the "...

In the case of the transmission of speech by radio we are interested in having no interference from other signals which are within 2000 cycles of the frequency of our radio-curr...

The simplest wire telephone-circuit is formed by a transmitter, a receiver, a battery, and the connecting wire. If two persons are to carry on a conversation each must have this...