Evening star., 1922-06-22

talk to him as readily as though he
were in the same room. Rememoer
not to carry on any conversation
which is private or which you do not
want others to hear, for there is no
privacy in the air and anyone anu
everyone within range can hear What
You are saying. In order to lnsta!l
and use a sending set you must Sc
cure a government license and must
be prepared to pass an examination
in order to get 1t. Moreover. you
must be sure and make set when
will comply with the government
regulations as to wave lengths: When
YOU decide that you must nave
sending set. the first thing TO CON
sstruct is an aerial for sendlhe.
Although a single wire answers ever
purpose for receiving and is as Soou
or better than a multiple wire an
,tenua, this is not the case in sending
and a new aerial must be arranged
for the purpose. Not only must thIs
be of the correct design. but it must
station transmitting on longer wave
tIenCths than YOUR amateurs license
permits.
Aerial Forms Differ.
The exact form of aerial does not
matter so much and you should select
that which best serves your location
and the spot whereon you place II.
Probab bly, the best form of aerial is
the cage type tFfgure u, consisting
of metal hoops over which paraiiei
wires are run to form an open work
cylinder The u type (F'igure y
is also good. as is the form with
lead-in from the center (Flgure 3A)
or with lead-in from both ends ttlS-
sure 3B) The pyramid or umbrella
type (Figure ~ is also good. In TINS
form the central iron or metal post
the guy wires also aerials. The post
must. of course be insulated from
the roof or other base on which IL
rests and each of the guy wires must
be thoroughly insulated from the ROOF
or base also. but. of course, connected
with the post at the top. Indeed.
almost any form of aerial with seN-
eral wires will answer for amateur
use but they should not be over sew
enty-flve feet long. The best way 10
erect such an aerial as those sho"n
is to attach the wires and spreaders
by means of insulators. attach the
lead-in at the proper place and then
hoist the entire affair to its posi-
tion. securing 1t by strong wires or
small wire ropes. Use insulators be-
tween the spreaders and the guys as
shown. The lead-in is then carried
TO the set as usual. but lightning
switch must be installed with
proper ground for a sending set.
Use of Counterpoise.
Very often a sending set may be
vastly improved by using a counter
poise instead of a ground. This is a
device resembling an aerial, which, il
placed under or near the aerial, elimi-
mates the necessity of a ground to
the set. Very little is really known
in regard to the counterpoise. In a
way it resembles a condenser, with
the difference that whereas a con-
denser radiates very little energy the
counterpoise radiates d great deal.
In using radio on airplanes the
metal parts of the fuselage or a spe-
Cial wire is used as a counterpoise,
and radio sets on motor cars utilize
the frame of the car for a counter
pose. In receiving a counterpolse
Is of little advantage and is not worth
the trouble of installation, but for
sending it is distinct advantage.
The best form of counterpoise is the
fan-shaped affair illustrated in Flg-
ure 5. This should by preference be
stretched below the aerial and as far
from it as possible. The ideal posi-
ton is near the ground and about
three feet from it, but as a counter
poise at that height is always more
or less in the way, it is better to
raise it about seven feet above the
ground. SO as to clear the heads of
anyone walking under 1t. The wires
should be attached to stout stakes by
means of insulators as shown, for it
IS just as important to insulate the