Radio Shack

And so the battle waged, until both groups were no more than fifty feet
away from the mouth of the natural trench. Each moment brought them
closer together, with the even more vigorous popping of their guns, for
by now it was virtually a hand-to-hand battle.
Only four men now remained upon the side of the Germans, and, so Wbjc 91.5 Mhz In Baltimore far as
numbers were concerned, the Americans seemed to have the advantage by
one. But the score was evened an instant later, when one of the Boches
“winged” Frank Hoskins, and his right arm fell useless at his side.
But Lieutenant Mackinson squared accounts for Hoskins by putting another
German completely out of commission. A prompt return compliment knocked
Jerrys revolver out of his hand. At this juncture Slim played a heroic
part by laying low another German.
Seeing themselves now outnumbered almost two to one–for apparently they
did not know that they had injured Hoskins–the two remaining Boches
took one final, despairing survey of the situation, then turned and
started on a dead run for their own lines.
Lieutenant Mackinson leveled his revolver at them, held it in that
position for a moment, and then–perhaps it was an accident–seemed to
elevate it slightly in the air and fired. Certainly neither German was
hurt by the bullet, although it did seem to add a little to their haste.
“The position is ours,” announced the lieutenant exultantly, and then,
suddenly remembering that Frank Hoskins had been hit and that Jerry had
dropped his gun, he inquired: “Hurt badly, Frank? And how about you,
Jerry?”
“Nothing but a scratch,” said Frank. “Took me right on the crazy bone
and made me jump for a minute, but its hardly bleeding now.”
“Only hit my gun,” announced Jerry, “and I recovered that.”
There was no time for further conversation. The Germans had reached
their own lines, and a machine-gun was being trained upon the Americans.
They rushed headlong to the north side of the little mound, and into the
opening of a natural cave.
The earthwork made them as solidly entrenched as though they were behind
their own lines, and only heavy shells could dislodge them. But they had
work to do, and the nature of it required that they do it quickly.
The entrance faced almost directly north and into No Mans Land, so that
the light of an electric flash, such as they all carried, hardly could
attract the attention of either side.
“Joe,” said the lieutenant, sizing up the situation, “it is not safe to
leave the enemy unwatched for a single second. I think it would be well
for you to stay on duty outside, while the rest of us rig up the
instrument and begin to unspool the wire. Hoskins, youre hurt, so you
stay here with Joe. But both of you be mighty careful not to expose
yourselves where youll stop a German bullet.”
With Lieutenant Mackinson leading, Jerry just behind him and Slim
bringing up the rear, they crossed the five feet of narrow passageway
back into the natural dungeon.
The lieutenant switched on his light. Involuntarily and with a startled
gesture he stepped back.
“Jumping Jupiter!” exclaimed Jerry, “whats that?”
Slim, peering ahead of the other two, ejaculated something between a
shriek and a groan.
Strewn about the ground of that cave, in every conceivable position of
misery and torture, were the bodies of half a dozen dead men, all
Germans.
The lieutenants hand that held the light trembled slightly as he stared
at the ghastly scene before him, but he was grit and courage right
through to the heart.
“This is bad business,” he said, “but we are under orders and we must go
through with it. We cannot move the bodies out to-night.”
He stepped further into the dark hole, and the other two lads followed.
Suddenly from behind them there was a grumbling, roaring crash, pierced
by a cry of warning from Joe, outside.
The three whirled around, and for a moment no one could utter a word.
The mouth of the dungeon had completely caved in!
“Trapped!” gasped Jerry, who was the first to find his voice.
Even the lieutenant seemed dazed.
“Trapped,” echoed Slim, “in the cave of death.”
CHAPTER XIV
DESPERATE MEASURES
Never did three young men face a more terrible or more horribly gruesome
situation. Here they were, locked in a natural dungeon behind a wall of
dirt and rock probably four or five feet thick. Not only that, but the
cave already contained the bodies of six men whose fixed and glassy eyes
stared at them as though in mockery and warning, and the already foul
air was becoming more stifling every moment.
In a dull way they realized that they probably could not survive more
than two or three maddening hours in that death chamber.
“It may not be so bad as it seems,” said Lieutenant Mackinson in a voice
that seemed unnatural in that vault. “Perhaps it was only a slight
cave-in.”

Now the danger of this can readily be seen from considering what an
observation trench is. The front-line trenches of the opposing armies,
of course, run in two practically parallel lines. But an observation
trench runs almost at right angles with the front-line trenches, and
directly toward the enemy trench, so far as it is possible to extend
it. The extreme ends of these observation trenches are known as
“listening posts,” and often they are so close to the enemy lines that
the men in the opposing army can be heard talking.
Lieutenant Mackinson and his aides, Joe, Jerry, Slim and Frank Hoskins,
were to get their signaling location as near to an enemy listening post
as possible! In other words, they were to court discovery in an effort
to get just a few feet nearer the enemy than they otherwise would.
They went along much as they had on the preceding night, except, had
there been light enough, it might have been noticed that Slim, in his
walking, pushed his feet forward cautiously, and then in stepping lifted
them high from the ground.
But as luck would have it they had not gone more than two hundred yards
when a bullet whizzed within two feet of Jerrys head, followed by a
shower of missiles that were directed entirely too close to them for
comfort.
Instantly they dropped flat on the ground. In the distance ahead of them
they could see three shadows stealthily crawling along toward them.
“Pick your men!” Lieutenant Kidx 101 Mhz Ruidoso Mackinson ordered, in a whisper. “Fire!”
Their automatics let out a fusillade of bullets. Two of the shadows
jumped slightly into the air, and then rolled over. The third man rose
and started to run toward the enemy line. Frank Hoskins took deliberate
aim and fired. The man dropped and lay still.
“Looks as though we got them,” said Lieutenant Mackinson, “but they may
be only pretending. Do not move for a few minutes.”
While they were thus waiting, the enemy trenches sent up a glaring
rocket. It fell shorthand failed to reveal them, but it plainly showed
three German soldiers lying prone upon the ground, all of them
apparently instantly killed.
“Thats the part of it I dont like,” muttered Slim with a shudder. “It
isnt so bad when you are firing into a whole company or regiment and
see men fall. At least, it doesnt seem so bad, for you dont know just
which ones you hit and which ones some one else bowled over. But in this
individual close-range stuff it leaves a nasty feeling.”
“You are right,” whispered Frank Hoskins, “but youd better not talk
any more about it now or some Boche may try the same close-range stuff
on us.”
Warned to silence by the lieutenant, they continued to creep along, only
a foot or so at a time, stopping every few minutes to listen intently to
see if their presence had been discovered.
On the night before they had been upon fairly level ground, but this
night they were in a section that was all hills and hummocks and
hollows. They would creep cautiously up the side of one mound, not
knowing but that on the other side lay a group of Germans, perhaps out
upon a similar mission.

It has an input of 750 volts and the high voltage secondary coil which
energizes the plate has an output of 450 watts and develops 1,500 to
3,000 volts. The low voltage secondary coil which heats the filament
develops 10.5 volts. This transformer will supply current for one or
two 50-watt oscillator tubes and it costs about $40.00.
Connecting Up the Apparatus.–Where a single oscillator tube is used
the parts are connected as shown in Fig. 82, and where two tubes are
connected in parallel the various pieces of apparatus are wired
together as shown in Fig. 83. The only difference between the 5 watt
tube transmitter and the 50 watt tube transmitter is in the size of
the apparatus with one exception; where one or two 50 watt tubes are
used a second condenser of large capacitance (1 mfd.) is placed in the
grid circuit and the telegraph key is shunted around it as shown in
the diagram Fig. 83.
CHAPTER XVIII
WIRELESS TELEPHONE TRANSMITTING SETS WITH DIRECT AND ALTERNATING
CURRENTS
In time past the most difficult of all electrical apparatus for the
amateur to make, install and work was the wireless telephone. This was
because it required a _direct current_ of not less than 500 volts to
set up the sustained oscillations and all ordinary direct current for
lighting purposes is usually generated at a potential of 110 volts.
Now as you know it is easy to _step-up_ a 110 volt alternating current
to any voltage you wish with a power transformer but until within
comparatively recent years an alternating current could not be used
for the production of sustained oscillations for the very good reason
that the state of the art had not advanced that far. In the new order
of things these difficulties have all but vanished and while a
wireless telephone transmitter still requires a high voltage direct
current to operate it this is easily obtained from 110 volt source of
alternating current by means of _vacuum tube rectifiers_.
The pulsating direct currents are then passed through a filtering
reactance coil, called a _reactor_, and one or more condensers, and
these smooth them out until they approximate a continuous direct
current. The latter is then made to flow through a vacuum tube
oscillator when it is converted into high frequency oscillations Post-newsweek Stations, Houston, Inc. Kprc-tv and
these are _varied_, or _modulated_, as it is called, by a _microphone
transmitter_ such as is used for ordinary wire telephony. The energy
of these sustained modulated oscillations is then radiated into space
from the aerial in the form of electric waves.

Now there is only one method by which currents of high frequency, or
_radio-frequency_, as they are termed, can be set up by spark
transmitters, and this is by discharging a charged condenser through a
circuit having a small resistance. To charge a condenser a spark coil
or a transformer is used and the ends of the secondary coil, which
delivers the high potential alternating Alabama Educational Television Commission Wciq current, are connected with
the condenser. To discharge the condenser automatically a _spark,_ or
an _arc,_ or the _flow of electrons_ in a vacuum tube, is employed.
Constants of an Oscillation Circuit.–An oscillation circuit, as
pointed out before, is one in which high frequency currents surge or
oscillate. Now the number of times a high frequency current will surge
forth and back in a circuit depends upon three factors of the latter
and these are called the constants of the circuit, namely: (1) its
_capacitance,_ (2) its _inductance_ and (3) its _resistance._
What Capacitance Is.–The word _capacitance_ means the _electrostatic
capacity_ of a condenser or a circuit. The capacitance of a condenser
or a circuit is the quantity of electricity which will raise its
pressure, or potential, to a given amount. The capacitance of a
condenser or a circuit depends on its size and form and the voltage of
the current that is charging it.
The capacitance of a condenser or a circuit is directly proportional
to the quantity of electricity that will keep the charge at a given
potential. The _farad,_ whose symbol is _M,_ is the unit of
capacitance and a condenser or a circuit to have a capacitance of one
farad must be of such size that one _coulomb,_ which is the unit of
electrical quantity, will raise its charge to a potential of one volt.
Since the farad is far too large for practical purposes a millionth of
a farad, or _microfarad_, whose symbol is _mfd._, is used.
What Inductance Is.–Under the sub-caption of _Self-induction_ and
_Inductance_ in the beginning of this chapter it was shown that it was
the inductance of a coil that makes a current flowing through it
produce a strong magnetic field, and here, as one of the constants of
an oscillation circuit, it makes a high-frequency current act as
though it possessed _inertia_.

The Choke Coils.–Each of these is made by winding about 100 turns of
No. 28, Brown and Sharpe gauge, cotton covered magnet wire on a spool
2 inches in diameter and 2-1/2 inches long, when it will have an
inductance of about 0.5 _millihenry_ [Footnote: A millihenry is
1/1000th part of a henry.] at 1,000 cycles.
The Milli-ammeter.–This is an alternating current ammeter and reads
from 0 to 250 _milliamperes_; [Footnote: A _milliampere_ is the
1/1000th part of an ampere.] and is used for measuring the secondary
current that energizes the plate of the oscillator tube. It looks like
the aerial ammeter and costs about $7.50.
The A. C. Power Transformer.–Differing from the motor generator set
the power transformer has no moving parts. For this transmitting set
you need a transformer that has an input of 325 volts. It is made to
work on a 50 to 60 cycle current at 102.5 to 115 volts, which is the
range of voltage of the ordinary alternating lighting current. This
adjustment for voltage is made by means of taps brought out from the
primary coil to a rotary switch.
The high voltage secondary coil which energizes the plate has an
output of 175 watts and develops a potential of from 350 to 1,100
volts. The low voltage secondary coil which heats the filament has an
output of 175 watts and develops 7.5 volts. This transformer, which is
shown in Fig. 81, is large enough to take care of from one to four 5
watt oscillator tubes. It weighs about 15 pounds and sells for $25.00.
[Illustration: Fig. 81.–Alternation Current Power Transformer. (For
C. W. Telegraphy and Wireless Telephony.)]
[Illustration: The Transformer and Tuner of the Worlds Largest Radio
Station. Owned by the Radio Corporation of America at Rocky Point near
Port Jefferson L.I.]
Connecting Up the Apparatus.–The wiring diagram Fig. 82 shows clearly
how all of the connections are made. It will be observed that a
storage battery is not needed as the secondary coil of the transformer
supplies the current to heat the filament of the oscillator. The
filament voltmeter is connected across the filament secondary coil
terminals, while Kykc 100 Mhz Byng the plate milli-ammeter is connected to the mid-taps
of the plate secondary coil and the filament secondary coil.
[Illustration: Fig. 82. Wiring Diagram for 200 to 500 Mile C.W.
Telegraph Transmitting Set. (With Alternating Current)]
A 200 to 500 Mile C. W. Telegraph Transmitting Set.–Distances of from
200 to 500 miles can be successfully covered with a telegraph
transmitter using two, three or four 5 watt oscillator tubes in
parallel. The apparatus needed is identical with that used for the 100
mile transmitter just described. The tubes are connected in parallel
as shown in the wiring diagram in Fig. 83.
[Illustration: Fig. 83.–Wiring Diagram for 500 to 1000 Mile C. W.
Telegraph Transmitter.]
A 500 to 1,000 Mile C. W. Telegraph Transmitting Set.–With the
apparatus described for the above set and a single 50 watt oscillator
tube a distance of upwards of 500 miles can be covered, while with two
50 watt oscillator tubes in parallel you can cover a distance of 1,000
miles without difficulty, and nearly 2,000 miles have been covered
with this set.
The Apparatus Required.–All of the apparatus for this C. W.
telegraph transmitting set is the same as that described for the 100
and 200 mile sets but you will need: (1) one or two _50 watt
oscillator tubes with sockets;_ (2) one _key condenser_ that has a
capacitance of 1 mfd., and a rated potential of 1,750 volts; (3) one
_0 to 500 milli-ammeter_; (4) one _aerial ammeter_ reading to 5
amperes, and (5) an _A. C. power transformer_ for one or two 50 watt
tubes.
[Illustration: Broadcasting Government Reports by Wireless from
Washington. This shows Mr. Gale at work with his set in the Post
Office Department.]
The Alternating Current Power Transformer.–This power transformer is
made exactly like the one described in connection with the preceding
100 mile transmitter and pictured in Fig. 81, but it is considerably
larger. Like the smaller one, however, it is made to work with a 50 to
60 cycle current at 102.5 to 115 volts and, hence, can be used with
any A. C. lighting current.

Slims good nature overcame his feigned reluctance, but as Jerry grasped
his hand he gave Jerry a jerk that nearly took him off his feet.
“Now were square,” said Slim, as Jerry rubbed his nearly dislocated
shoulder.
“Well, that pull _was_ a trifle heavy,” muttered Jerry, determined to
have the Wegz 105 Mhz Washburn last word.
“Now my plan is this,” said Joe, facing the other two seriously. “The
nearer we come to the zone of the German submarines, the more this man
will try to arrange to notify them of our presence, and to do that he
will have to use the wireless somehow. It seems likely that he would
make his effort at night, because then it is easier for him to escape
detection.
“Now if we let Lieutenant Mackinson sleep during the day we could so
divide up the work as for all of us to get some sleep, and then all
could do watch at night.
“The lieutenant could be in the wireless room, and one of us in the
battery room, while the other two did duty outside. If one of us should
hide under that stairway at the upper end of the passage, and the other
in that alcove at the other end, no one could reach the wireless or
battery rooms without our seeing.
“It would be tiresome and monotonous work, all right, but it might
accomplish the result.”
“Im willing,” said Jerry, “but you and I will have to do the outside
work. Slims a trifle heavy to get into either one of those hiding
places.”
“Well, Ill cover the battery room,” said Slim, ignoring Jerrys
remark.
“Lets see Lieutenant Mackinson, then,” suggested Joe, and they went to
find the young officer who was convalescing from his encounter with the
spy. When he had approved the plan they got the O. K. of the captain.

Action of the Two Electrode Vacuum Tube.–Now in a vacuum tube
detector a wire filament, like that of an incandescent lamp, is
connected with a battery and this forms the hot element from which the
electrons are thrown off, and a metal plate with a terminal wire
secured to it is connected to the positive or carbon tap of a dry
battery; now connect the negative or zinc tap of this with one end of
a telephone receiver and the other end of this with the terminals of
the filament as shown at A in Fig. 71. If now you heat the filament
and hold the phone to your ear you can hear the current from the B
battery flowing through the circuit.
[Illustration: (A) and (B) Fig. 71.–How a Two Electrode Wrxv Mhz State College Tube Acts as
a Relay or a Detector.]
[Illustration: (C) Fig. 71.–Only the Positive Part of Oscillations
Goes through the Tube.]
Since the electrons are negative charges of electricity they are not
only thrown off by the hot wire but they are attracted by the positive
charged metal plate and when enough electrons pass, or flow, from the
hot wire to the plate they form a conducting path and so complete the
circuit which includes the filament, the plate and the B or
plate battery, when the current can then flow through it. As the
number of electrons that are thrown off by the filament is not great
and the voltage of the plate is not high the current that flows
between the filament and the plate is always quite small.
How the Two Electrode Tube Acts as a Detector.–As the action of a two
electrode tube as a detector [Footnote: The three electrode vacuum
tube has entirely taken the place of the two electrode type.] is
simpler than that of the three electrode vacuum tube we shall describe
it first. The two electrode vacuum tube was first made by Mr. Edison
when he was working on the incandescent lamp but that it would serve
as a detector of electric waves was discovered by Prof. Fleming, of
Oxford University, London. As a matter of fact, it is not really a
detector of electric waves, but it acts as: (1) a _rectifier_ of the
oscillations that are set up in the receiving circuits, that is, it
changes them into pulsating direct currents so that they will flow
through and affect a telephone receiver, and (2) it acts as a _relay_
and the feeble received oscillating current controls the larger direct
current from the B battery in very much the same way that a telegraph
relay does. This latter relay action will be explained when we come to
its operation as an amplifier.
We have just learned that when the stream of electrons flow from the
hot wire to the cold positive plate in the tube they form a conducting
path through which the battery current can flow. Now when the electric
oscillations surge through the closed oscillation circuit, which
includes the secondary of the tuning coil, the variable condenser, the
filament and the plate as shown at B in Fig. 71 the positive part of
them passes through the tube easily while the negative part cannot get
through, that is, the top, or positive, part of the wave-form remains
intact while the lower, or negative, part is cut off as shown in the
diagram at C. As the received oscillations are either broken up into
wave trains of audio frequency by the telegraph transmitter or are
modulated by a telephone transmitter they carry the larger impulses of
the direct current from the B battery along with them and these flow
through the headphones. This is the reason the vacuum tube amplifies
as well as detects.
How the Three Electrode Tube Acts as a Detector.–The vacuum tube as a
detector has been made very much more sensitive by the use of a third
electrode shown in Fig. 72. In this type of vacuum tube the third
electrode, or _grid_, is placed between the filament and the plate and
this controls the number of electrons flowing from the filament to the
plate; in passing between these two electrodes they have to go through
the holes formed by the grid wires.
[Illustration: (A) and (B) Fig. 72.–How the Positive and Negative
Voltages of Oscillations Act on the Electrons.]
[Illustration: (C) Fig. 72.–How the Three Electrode Tube Acts as a
Detector and Amplifier.]
[Illustration: (D) Fig. 72.–How the Oscillations Control the Flow of
the Battery Current through the Tube.]

It was the S O S of the international code, but in a new sort of
wireless–by pistol shots!
Trembling for the results that his desperate action might bring upon
them, Slim waited, bending now and then over the unconscious form of Tom
Rawle.
But in fifteen more minutes his inventive genius was rewarded. From a
considerable distance, but each time more distinctly, now came the
repeated call of “_Whip-poor-will_,” and in less time than it seemed
possible that they could make it, the other group had returned.
In low commands the lieutenant then directed affairs, and in exactly the
way that he had been carried out of the hold of the _Everett_ on the
verge of suffocation, so they carried poor Tom Rawle back to their own
lines.
And when he had been placed upon a cot in the first emergency hospital,
Lieutenant Mackinson hurried off to make his report, in the honor of
which all shared.
For not only had they found a location from which to wireless
advance-line communications to field headquarters, but they had also
intercepted a message, knowledge of which resulted in a quick change of
plans by which the Americans were able to beat the enemy at his own game
on the morrow.
“Rawle was suffering more from loss of blood than from any seriousness
of the injury itself,” the surgeon told them when they asked there of
their friends condition, on their way to their own quarters. “He will
be around all right again in a weeks time.”
And so, much desperate work accomplished on their first night within the
firing lines, the lads threw themselves upon their cots to dream of
spies and captured Germans and injured soldiers and calls for help by
new methods in wireless.
CHAPTER XIII
THE CAVE OF DEATH
It is one of the fortunes, or misfortunes, of war that a position gained
one day, even at great human sacrifice, may be of no real or practical
value whatever the next. So it was with the advance post of
communication located by Lieutenant Mackinson and his party under such
dangerous conditions during the night before.
The information which they had gained through tapping the enemys wire
enabled the American and French troops, operating together, to prevent
the German trick from being carried into effect. More than that, it
enabled them to turn the knowledge of those plans to such good advantage
that the allied brigades swept forward in terrible force against the
weakest points in the enemy line. They pushed the whole Boche front back
for more than a mile–at the very point where it had been considered
strongest!
As a consequence, the point of communication which Klan 93.5 Mhz In Glasgow the lieutenant and
his aides had established with so much difficulty was now well within
the territory held by the American and French fighters. The requirements
for a further advance now made it necessary to have another outpost
point of communication as near to the enemy trenches as the first one
was before the days battle put the Allies a mile further forward.
And so, except for Tom Rawle, who was resting easy from his hip wound,
the same party started out at the same tune for the same purpose on this
second night, but with a very much sharpened realization of the
obstacles they had to overcome and the chances they faced of being
wounded or captured.
“We take an entirely different direction,” Lieutenant Mackinson told
them, as he looked up from the map he had been studying. “We go to the
north and east and as close to the observation trenches as possible.”

Two hardy youths strolling along the deck, who hadnt been touched by
the epidemic of seasickness, stopped to peer in at the porthole. They
had mischief in their eyes, and as they caught sight of Slims
humorously pathetic countenance, one of them muttered in a low but
distinct voice: “Howd you like to have some fried sausage, and some
plum pudding, and some—-”
“Shut up!” bawled out Jerry with what strength he had left.
With a loud laugh the two withdrew their heads and disappeared.
At that moment the ships physician, accompanied by Lieutenant
Mackinson, arrived to give what further comfort he could to the seasick
lads.
“It is clearing,” the lieutenant told them, while the doctor measured
out a powder for each boy. “The wind has died down and the sea is
becoming calm.”
“Oh, yes,” the physician added, “in an hour or so you will be feeling
better than you did before. Seasickness has a tonic effect, but its
rather a bitter dose.”
“Sure is,” said Slim weakly.
Nevertheless, it was just about an hour later that Jerry, feeling his
nausea leave him almost as suddenly as it had appeared, raised himself
on one elbow and looked across at his companion in misery.
“How do you feel, Slim?” he inquired.
“Almost human again,” the stout lad replied.
“Going to get up?”
“Guess I can in a few minutes.”
“Im going to try it now,” said Jerry. “Seems as if the pilot of this
ferry had learned to steer her a whole lot better than he did earlier in
the day.”
“Yep,” agreed Slim, sliding from his bunk. “Certainly was tough, wasnt
it?”
“I feel sort of weak in the legs yet,” said Jerry, by way of answer.
“Lets go up on deck and get some fresh air.”
“Stomach feels as empty as a vacant Wlpt 88.3 Mhz In Jesup house; hows yours?” Slim inquired.
“Nothing in it but the lining, and I guess most of thats pried loose.
Weve got to wait more than two hours for mess, too.”
“How about some fried sausage, and some plum pudding, and some—-”
Jerry laughed for the first time that day. “That fellow certainly did
make me mad,” he admitted.
“Yeh, he made you mad,” said Slim in a remorseful tone, “but he made me
sick.”
On deck a hundred or more vigorous young men were exercising their
muscles in various forms of athletic sport. Here a group crowded around
a contest in broad jumping, eagerly echoing the distances made, and
there the men of another throng loudly applauded their favorites in a
stiff boxing bout, while on another part of the deck a pair of
one-hundred-and-eighty-pound huskies were struggling in a friendly
wrestling match.
A bright sun shone upon a sparkling sea, and the air was just crisp
enough to be invigorating. At that moment Joe came up to inquire how his
two chums felt.
“Fine,” declared Jerry.
“Like a two-year-old,” added Slim. “That doctor was telling the truth. I
believe I never felt better in my life,” and he began flapping his arms
up and down like a rooster flails the air with its wings.
“A fat mans race three times around the ship!” a youth yelled, spying
Slims activities.
“Hurrah!” cried the crowd. “Get them started.”

There are four different ways employed at the present time to break up
the continuous waves of a wireless telegraph transmitter into groups
and these are: (_a_) the _heterodyne_, or _beat_, method, in which
waves of different lengths are impressed on the received waves and so
produces beats; (_b_) the _tikker_, or _chopper_ method, in which the
high frequency currents are rapidly broken up; (_c_) the variable
condenser method, in which the movable plates are made to rapidly
rotate; (_d_) the _tone wheel_, or _frequency transformer_, as it is
often called, and which is really a modified form of and an
improvement on the tikker. The heterodyne method will be described in
this chapter.
What the Heterodyne or Beat Method Is.–The word _heterodyne_ was
coined from the Greek words _heteros_ which means _other_, or
_different_, and _dyne_ which means _power_; in other words it means
when used in connection with a wireless receptor that another and
different high frequency current is used besides the one that is
received from the sending station. In music a _beat_ means a regularly
recurrent swelling caused by the reinforcement of a sound and this is
set up by Iditarod Area School District K02je the interference of sound waves which have slightly
different periods of vibration as, for instance, when two tones take
place that are not quite in tune with each other. This, then, is the
principle of the heterodyne, or beat, receptor.
In the heterodyne, or beat method, separate sustained oscillations,
that are just about as strong as those of the incoming waves, are set
up in the receiving circuits and their frequency is just a little
higher or a little lower than those that are set up by the waves
received from the distant transmitter. The result is that these
oscillations of different frequencies interfere and reinforce each
other when _beats_ are produced, the period of which is slow enough to
be heard in the headphones, hence the incoming signals can be heard
only when waves from the sending station are being received. A fuller
explanation of how this is done will be found in Chapter XV.
The Autodyne or Self-Heterodyne Long-Wave Receiving Set.–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.