American Agriculturist, March 31,1923 
299 
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As a part of our broad policy of 
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You May Be Hurt or 
Killed In a Train or 
Auto Accident 
Tomorrow 
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This Tells You What 
the Policy Will Pay 
The North American Accident In¬ 
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the policy, for death or disability on 
a public carrier, due to its wrecking or 
disablement while the insured is riding 
as a fare-paying passenger, or due to 
the wrecking or disablement of any 
private horse-drawn or motor-driven 
vehicle on which insured may be riding 
or driving, or by being thrown there¬ 
from. 
Life One Thousand Dollars ($1,000.00) 
Both Hands 
One Thousand Dollars ($1,00.0.00) 
Both Feet 
One Thousand Dollars ($1,000.00) 
Sight of Both Eyes 
One Thousand Dollars ($1,000.00) 
One Hand and One Foot, 
One Thousand Dollars ($1,000.00) 
Either Hand and Sight of One Eye, 
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Either’Foot and Sight of One Eye, 
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Sight of Either Eye 
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Two Hundred and Fifty Dollars ($250.00) 
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for one year. Enclosed find $2.50 in full pay- 
ment for both the policy and subscriptions. 
I What Is a “Loop” Antenna? 
A Radio Talk on an Indoor Aerial 
W ITH the develop¬ 
ment of radio fre¬ 
quency amplification a concentrated 
form of aerial known as the “loop” has 
come into use. Essentially, a loop con¬ 
sists of a wooden or brass framework 
from two to four feet square, about 
which is wound in spiral or box-like 
style a number of turns of wire. 
Sometimes the loop is mounted ver¬ 
tically on a shaft which passes through 
its center, and others are mounted on 
an extension of one of the cross-arms, 
diamond shape. The loop is always ar¬ 
ranged so that it may be rotated about 
its axis. The two forms of mounting 
are equally effective. 
How does the loop function? A loop 
is nothing more or less than a coil of 
wire made up into a larger form than is 
customary for coils which are used in 
tuning a receiving set. Indeed, where 
there is a broadcasting station within 
a mile or two, it is often possible to 
pick up some of the speech and music 
without any aerial at all. The coil of 
the set is sufficient to intercept the 
waves and cause a response in the 
headphones. 
Locating the Loop 
T O make such a scheme operate sat- 
factorily, the coil is made larger for 
the express purpose of acting as a con¬ 
centrated aerial. When the loop is 
moved to such a position that the 
waves from the broadcasting station 
come parallel t6 it, in other words, 
when the flat plane of the loop is 
pointed directly toward the station, 
the signals are received with the 
greatest intensity. 
The wave first strikes on side of the 
loop and induces a current in its wires, 
just as we have found it to do in the 
case of the antenna. Then a bit later 
it comes to the other side, which is a 
little further from the source of the 
waves than the side of the loop which 
the w'ave first encountered. Here a 
current is induced in the other direc¬ 
tion. In this manner, current oscil¬ 
lating back and forth is set up in the 
loop, and it may be applied to the de¬ 
tector tube. Since the loop is in real¬ 
ity a coil such as the secondary wind¬ 
ing of a vario-coupler, it is necessary 
to provide some method by which it 
may be tuned to the respective wave 
lengths used by the different stations. 
This is done by a variable condenser 
of about 23 plates, connected to the 
two ends of the loop’s winding. 
Now, when the loop is turned so 
that it is at right angles to the direc¬ 
tion of the broadcasting station, the 
signals disappear. Why? Because the 
wave strikes the two sides of the loop 
exactly at the same instant, and the 
current in one side is nullified by that 
in the other. Right here we may rec¬ 
ognize one of the great advantages of 
the loop over the outside aerial. The 
latter is only slightly directive, but 
with the loop, the remarkable direc¬ 
tional properties enable us to tune out 
or select between two stations operat¬ 
ing on exactly the same wave length, 
providing they are in different direc¬ 
tions from the set. 
A Valuable Property 
T his property of the loop was inval¬ 
uable during the World War, when 
loops were used by the French and 
American armies to locate enemy radio 
stations both on the ground and on 
board aeroplanes. Loop stations were 
erected ten or twenty miles apart, and 
“bearings” taken when the enemy sta¬ 
tions were transmitting. The direc¬ 
tions obtained by the several stations 
were plotted on a map at the central 
office, and the position of the station 
indicated by the point at which all the 
lines crossed. To-day this system is 
employed by the naval “Compass” sta¬ 
tions, and ships’ positions are furnished 
to captains who are a bit uncertain 
during fogs and thick weather. 
Another point in favor of the loop is 
its extreme selectivity. One or two 
degrees movement of the condenser 
serves to tune out a station alto¬ 
gether and pick up another one. 
This is especially useful when dis¬ 
tant or “DX” reception is being 
attempted while a nearby station is 
operating on almost the same wave 
length. Radio fre- 
quency amplification 
will be covered in the next radio 
article in the American Agriculturist, 
with especial emphasis on the “reflex” 
circuit which has won its way into the 
broadcast field. 
In this circuit, which may be used 
for either loop or outside antenna, 
the vacuum tubes are used along with 
a crystal detector in such a manner 
that long-distance work is provided by 
radio frequency, while signal strength 
is given by audio frequency, both on 
the same tubes. 
The Valley of the Giants 
{Continued from page 298) 
Ogilvy had called first on the Mayor 
to arrange the details; then he had 
called on the Mayor’s son to complete 
the transaction. 
(5) If a franchise had been arranged 
for and the bribe already delivered, 
that meant the prompt and unadver¬ 
tised commencement of operations. 
Where (the Colonel asked himself) 
would these operations begin? Why, 
close to the waterfront, where ma¬ 
terials could be landed from the 
steamer. At whose mill-dock would 
those materials be discharged? Why, 
Cardigan’s, of course. Yes, the N. C. 0. 
was going to carry its monumental 
bluff to the point of building a mile 
of track through town. , . . No—no, 
they wouldn’t spend that much money 
on a bluff; or bribe Poundstone unless 
the road was meant. And was it a 
common carrier, after all? Had Cardi¬ 
gan in some mysterious manner man¬ 
aged to borrow enough money to paral¬ 
lel the Laguna Grande Lumber Com¬ 
pany’s loggingroad, and was he disguis¬ 
ing it as a common carrier? 
The Colonel mopped his brow and 
concentrated further. If the N. C. O. 
was really going to start, in order to 
move its material from the Cardigan 
dock to the scene of operations it would 
have to cut the Colonel’s tracks some¬ 
where on Water Street. That was it! 
They were planning to get a jump¬ 
crossing in before he should awake to 
the situation; and once the crossing 
should be in, they could laugh at Colo¬ 
nel Pennington! 
“The scoundrels!” he murmured. “I’m 
on to them! Cardigan is playing the 
game with them. That’s why he bought 
those rails from the old Laurel Creek 
spur! Oh, the sly young fox to fool me 
into thinking he wanted those rails for 
an extension of his logging-system! Oh, 
what a blithering idiot I have been! 
However, it’s not too late yet. Pound- 
stone is coming over to dinner Thurs¬ 
day night, and I’ll wring the swine dry 
before he leaves the house. And as for 
those rails.” 
He seized the telephone and fairly 
shouted to his exchange operator to 
get Jules Rondeau. 
“That you. Rondeau?” he shouted 
when the big French Canadian re¬ 
sponded. “What has young Cardigan 
done about those rails I sold him 
from the abandoned spur up Laurel 
Creek?” 
“He have two flat-cars upon ze spur 
now. Dose woods-gang of hees she tear 
up dose rails from ze head of ze spur 
and load in ze flat-cars.” 
“The cars haven’t left the Laurel 
Creek spur, then?” 
“No, she don’t leave yet.” 
“See to' it. Rondeau, that they do 
not leave. Understand? Cardigan’s 
woods-boss will ask you to send a 
switch-engine up to snake them out late 
this afternoon or to-morrow afternoon. 
Tell him the switch-engine is in the 
shop for repairs or is busy at other 
work—anything that will stall him off 
and delay delivery.” 
“Suppose Bryce Cardigan, she comes 
around and say ‘Why?’ ” Rondeau 
queried cautiously. 
“Kill him,” the Colonel retorted cooly. 
“It strikes me you and the Black 
Minorca are rather slow playing even 
with young Cardigan.” 
Rondeau grunted. “I theenk mebbe 
so you kill heem yourself, boss,” he 
replied enigmatically, and hung up. 
{Continued next week) 
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