Radio Shack

Where this type of interrupter is employed the condenser that is
usually shunted around the break is not necessary as the interrupter
itself has a certain inherent capacitance, due to electrolytic action,
and which is called its _electrolytic capacitance_, and this is large
enough to balance the self-induction of the circuit since the greater
the number of breaks per minute the smaller the capacitance required.
The Rotary Spark Gap.–In this type of spark gap the two fixed
electrodes are connected with the terminals of the secondary coil of
the power transformer and also with the condenser and primary of the
oscillation transformer. Now whenever any pair of electrodes on the
rotating disk are in a line with the pair of fixed electrodes a spark
will take place, hence the pitch of the note depends on the speed of
the motor driving the disk. This kind of a rotary spark-gap is called
_non-synchronous_ and it is generally used where a 60 cycle
alternating current is available but it will work with other higher
frequencies.
The Quenched Spark Gap.–If you strike a piano string a single quick
blow it will continue to vibrate according to its natural period. This
is very much the way in which a quenched spark gap sets up
oscillations in a coupled closed and open circuit. The oscillations
set up in the primary circuit by a quenched spark make only three or
four sharp swings and in so doing transfer all of their energy over to
the secondary circuit, where it will oscillate some fifty times or
more before it is damped out, because the high frequency currents are
not forced, but simply oscillate to the natural frequency of the
circuit. For this reason the radiated waves approach somewhat the
condition of continuous waves, and so sharper tuning is possible.
The Oscillation Transformer.–In this set the condenser in the closed
circuit is charged and discharged and sets up oscillations that surge
through the closed circuit as in _Set No. 1_. In this set, however, an
oscillation transformer is used and as the primary coil of it is
included in the closed circuit the oscillations set up in it produce
strong oscillating magnetic lines of force. The magnetic field thus
produced sets up in turn electric oscillations in the secondary coil
of the oscillation transformer and these surge Millard County K36fy through the aerial wire
system where their energy is radiated in the form of electric waves.
The great advantage of using an oscillation transformer instead of a
simple inductance coil is that the capacitance of the closed circuit
can be very much larger than that of the aerial wire system. This
permits more energy to be stored up by the condenser and this is
impressed on the aerial when it is radiated as electric waves.
How Receiving Set No. I Works.–When the electric waves from a distant
sending station impinge on the wire of a receiving aerial their energy
is changed into electric oscillations that are of exactly the same
frequency (assuming the receptor is tuned to the transmitter) but
whose current strength (amperage) and potential (voltage) are very
small. These electric waves surge through the closed circuit but when
they reach the crystal detector the contact of the metal point on the
crystal permits more current to flow through it in one direction than
it will allow to pass in the other direction. For this reason a
crystal detector is sometimes called a _rectifier_, which it really
is.

But soon they realized that this, too, was as hopeless as the pounding,
for it further exhausted the energy which the foul air was rapidly
sapping, without making any apparent opening in the thick earthen wall
that surrounded them.
“Well,” said Slim at last, gulping back his nausea, and smiling almost
in his old time way, “Im as anxious as anybody to keep up hope to the
last. But if this is to be our end, I guess we can face it as Americans
should.”
“Bravo!” exclaimed Lieutenant Mackinson, “I always knew that each one of
you fellows had the right sort of stuff in you.”
And Jerry, too, slapped him affectionately on the back.
“Slim,” he said, smiling over at his chum, and ready for his pun, even
under such circumstances, “my head is feeling a trifle heavy, but Im
game to stand up to the last.”
Thus they sat down to wait–for just what, they did not know–while at
that very moment, four feet away from them on the other side of the
wall, faithful Joe was setting up the flashlight exactly according to
directions.
For a few seconds he waited, and then, three times in quick succession,
a rocket went into the air from just behind the American lines.
Over there Captain Hallowell himself found the range, submitted it to
his most expert gunner, who verified it, and then they waited for the
three minutes to elapse, during which Joe was to seek a place of safety.
It was in that interval, too, that Fate intervened for those within the
cave, for they were sitting with their backs to the very point against
which the shell was to be directed.
“We need all our strength,” Lieutenant Mackinson was saying. “So long as
possible we want to remain in full possession of our senses. The air is
purer near the floor. I think it would be better to lie down.”
And following his suggestion and example, the other two stretched
themselves out in the middle of the cavern.
Within the American lines, at that point where a regiment of heavy
artillery was stationed, Captain Hallowell raised his hand in signal to
his gunner. Out on the parapet of the front trench an anxious colonel
was standing, regardless of all danger, a pair of powerful glasses to
his eyes. His vision was focused upon a little light far out in No Mans
Land.
Two hundred feet away from that light Joe and Frank Hoskins lay prone
upon the ground, silent, impatient, fearful, hoping.
With a quick motion the artillery captain swung his outstretched arm
downward. There was a roar, a flash, and a great shell tore through the
air. Out in No Mans Land there was a second explosion as the shell hit,
and the target–a flashlight–was blown to atoms.
Over in the German trenches a sentinel chuckled at the thought of
another wasted American shell, but out of the hole that that shell had
torn three pale, haggard, and exhausted youths were crawling to safety
and Gods fresh air. And across No Mans Land dashed two pals to greet
them.
American determination and American marksmanship had Wokw 102.9 Mhz In Curwensville saved three
American lives. The German sentinel might have his laugh if he liked.
It was hours later before the three who had been imprisoned learned how
their rescue had been effected; but they got an inkling of it as they
came within four hundred yards of the American-French front.
“What are you doing?” Lieutenant Mackinson had asked, as Joe brought the
party to a stop.
“Just a moment and you will see,” Joe had responded.
And, first in wonder and then with a dawning understanding, the other
three read off his flashed message:
“Signal Corps men, and whole party safe.”
CHAPTER XV
THE SURPRISE ATTACK–PROMOTION
During the week that followed, the lads were confined almost entirely to
regular routine work, with nothing particularly exciting. Frank Hoskins
elbow wound healed quickly, without any serious results; and Tom Rawle,
who had been under treatment at the field hospital, was able to get
about the camp, although still pale and weak, and limping considerably
from his injury.

A Cheap Transmitting Set (No. 1).–For this set you will need: (1) a
_spark-coil_, (2) a _battery_ of dry cells, (3) a _telegraph key_, (4)
a _spark gap_, (5) a _high-tension condenser_, and (6) an _oscillation
transformer_. There are many different makes and styles of these parts
but in the last analysis all of them are built on the same underlying
bases and work on the same fundamental principles.
The Spark-Coil.–Spark coils for wireless work are made to give sparks
from 1/4 inch in length up to 6 inches in length, but as a spark coil
that gives less than a 1-inch spark has a very limited output it is
best to get a coil that gives at least a 1-inch spark, as this only
costs about $8.00, and if you can get a 2- or a 4-inch spark coil so
much the better. There are two general styles of spark coils used for
wireless and these are shown at A and B in Fig. 18.
[Illustration: (A) and (B) Fig. 18.–Types of Spark Coils for Set. No.
1.]
[Illustration: (C) Fig. 18.–Wiring Diagram of Spark Coil]
A spark coil of either style consists of (_a_) a soft _iron core_ on
which is wound (_b_) a couple of layers of heavy insulated Redwood Improvement Corporation W64ac wire and
this is called the _primary coil_, (_c_) while over this, but
insulated from it, is wound a large number of turns of very fine
insulated copper wire called the _secondary coil_; (d) an
_interrupter_, or _vibrator_, as it is commonly called, and, finally,
(e) a _condenser_. The core, primary and secondary coils form a unit
and these are set in a box or mounted on top of a hollow wooden base.
The condenser is placed in the bottom of the box, or on the base,
while the vibrator is mounted on one end of the box or on top of the
base, and it is the only part of the coil that needs adjusting.
The vibrator consists of a stiff, flat spring fixed at one end to the
box or base while it carries a piece of soft iron called an _armature_
on its free end and this sets close to one end of the soft iron core.
Insulated from this spring is a standard that carries an adjusting
screw on the small end of which is a platinum point and this makes
contact with a small platinum disk fixed to the spring. The condenser
is formed of alternate sheets of paper and tinfoil built up in the
same fashion as the receiving condenser described under the caption of
_Fixed and Variable Condensers_, in Chapter III.
The wiring diagram C shows how the spark coil is wired up. One of the
battery binding posts is connected with one end of the primary coil
while the other end of the latter which is wound on the soft iron core
connects with the spring of the vibrator. The other battery binding
post connects with the standard that supports the adjusting screw. The
condenser is shunted across the vibrator, that is, one end of the
condenser is connected with the spring and the other end of the
condenser is connected with the adjusting screw standard. The ends of
the secondary coil lead to two binding posts, which are usually placed
on top of the spark coil and it is to these that the spark gap is
connected.

The Condensers.–For the aerial series condenser get one that has a
capacitance of .002 mfd. and that will stand a potential of 3,000
volts. [Footnote: The U C-1014 _Faradon_ condenser made by the Radio
Corporation of America will serve the purpose.] It is shown at C. The
other three condensers, see D, are also of the fixed type and may have
a capacitance of .001 mfd.; [Footnote: List No. 266; fixed receiving
condenser, sold by the Manhattan Electrical Supply Co.] the blocking
condenser should preferably have a capacitance of 1/2 a mfd. In these
condensers the leaves of the sheet metal are embedded in composition.
The aerial condenser will cost you $2.00 and the others 75 cents each.
[Illustration: (A) Fig. 75.–Apparatus for Experimental C. W.
Telegraph Transmitter.]
[Illustration: Fig. 75.–Apparatus for Experimental C. W. Telegraph
Transmitter.]
Waym 88.7 Mhz In Columbia The Aerial Ammeter.–This instrument is also called a _hot-wire_
ammeter because the oscillating currents flowing through a piece of
wire heat it according to their current strength and as the wire
contracts and expands it moves a needle over a scale. The ammeter is
connected in the aerial wire system, either in the aerial side or the
ground side–the latter place is usually the most convenient. When you
tune the transmitter so that the ammeter shows the largest amount of
current surging in the aerial wire system you can consider that the
oscillation circuits are in tune. A hot-wire ammeter reading to 2.5
amperes will serve your needs, it costs $6.00 and is shown at E in
Fig. 75.
[Illustration: United States Naval High Power Station, Arlington Va.
General view of Power Room. At the left can be seen the Control
Switchboards, and overhead, the great 30 K.W. Arc Transmitter with
Accessories.]
The Buzzer and Dry Cell.–While a heterodyne, or beat, receptor can
receive continuous wave telegraph signals an ordinary crystal or
vacuum tube detector receiving set cannot receive them unless they are
broken up into trains either at the sending station or at the
receiving station, and it is considered the better practice to do this
at the former rather than at the latter station. For this small
transmitter you can use an ordinary buzzer as shown at F. A dry cell
or two must be used to energize the buzzer. You can get one for about
75 cents.
The Telegraph Key.–Any kind of a telegraph key will serve to break up
the trains of sustained oscillations into dots and dashes. The key
shown at G is mounted on a composition base and is the cheapest key
made, costing $1.50.
The Vacuum Tube Oscillator.–As explained before you can use any
amplifying tube that is made for a plate potential of 100 volts. The
current required for heating the filament is about 1 ampere at 6
volts. A porcelain socket should be used for this tube as it is the
best insulating material for the purpose. An amplifier tube of this
type is shown at H and costs $6.50.
The Storage Battery.–A storage battery is used to heat the filament
of the tube, just as it is with a detector tube, and it can be of any
make or capacity as long as it will develop 6 volts. The cheapest 6
volt storage battery on the market has a 20 to 40 ampere-hour capacity
and sells for $13.00.
The Battery Rheostat.–As with the receptors a rheostat is needed to
regulate the current that heats the filament. A rheostat of this kind
is shown at I and is listed at $1.25.
The Oscillation Choke Coil.–This coil is connected in between the
oscillation circuits and the source of current which feeds the
oscillator tube to keep the oscillations set up by the latter from
surging back into the service wires where they would break down the
insulation. You can make an oscillation choke coil by winding say 100
turns of No. 28 Brown and Sharpe gauge double cotton covered magnet
wire on a cardboard cylinder 2 inches in diameter and 2-1/2 inches
long.
Transmitter Connectors.–For connecting up the different pieces of
apparatus of the transmitter it is a good scheme to use _copper
braid_; this is made of braided copper wire in three sizes and sells
for 7,15 and 20 cents a foot respectively. A piece of it is pictured
at J.

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.