Evening star., 1926-04-18
No. 6O.--Why Is a Ground?

Smith had been obtaining such won
derful results from his set it seemed
that he could do away with some of
the details and still enjoy good recep-
tion; at least, from neaby stations
On several occasions he had dispensed
with the aerial. using nothing but his
hand on the aerial binding post. The
result rather startled him. Another
time he cut the 'B'' battery power by
half and still found the going very
good. Cutting out a stage OF audio
amplification had been still another
way of proving that average results
could be had under some conditions
with less equipment.
1t was not until he tried to get along
without the ground" however, that
his troubles began.
|. That's strange" he said, noting
that he wasn't getting anything on the
set. The ground is only part of
the wave intercepting system. | don't
see why I can dispense with one part
for nearby, or powerful, stations and
not another
That is because in your particular
set and hook-up the ground is the
most efficient part of the wave inter
cepting system, and, therefore, the
most essential" ! explained.
This gave the situation a different
twist. 1t reminded Smith that there
was another kind of Wave-intercepting
system and that in each system there
are certain features more important
than others.
Two Common Systems.
Roughly speaking, the two common
systems for picking the energy out of
| the air are the antenna-ground and
i, the loop arrangements. The latter is
story in itself. but just to help him
perceive the law of compensation
| more clearly I mentioned that while
| the loop arrangement was more con-
venient and utilized no ground con-
nection whatever, it picked up less
! energy than a we'll designed antenna-
ground arrangement Accordingly, 1t
| is necessary to use the former with a
| super sensitive set, such as super
heterodyne or a reflex hook-up of the
| highest order.
With good antenna-g ground system
| less is required in the way of receiv-
ing apparatus. And to drive home to
him the Importance of compensation
in all such matters l mentioned that
while system using the conventional
antenna with a ground" picks up
| ment tends to magnify set noises,
since the tubes are working with less
| outside" material.
Smith had been using an aerial com
posed of condenser plug inserted
| into the electric light socket. With
| the excellent ground" he used this
| made a good combination. But the
! antenna was less efficient than the
| ground" which meant that while he
| occasionally could dispense with the
| former. it was not possible to forego
use of the latter.
You mean that if I put up longer
| antenna on the roof / can do away
with the 'ground'?" he asked.
| Ny answer to that was an emphatic
No" Aren't you forgetting some of
the first principles about antennae?"
| reminded him. Where you use a
straight wire to intercept the radio
waves you are up against problem
| of inefficiency. The idea is to get the
| antenna wire as near to the length OF
the wave to be intercepted as possible,
! but the longer the wire the more radio
| energy Is picked up. You have to com
promise. You have to keep your wire
somewhere within reason. around 125
| feet in most cases. Your handicaps in
this connection. however, are offset by
the use of a good ground
THE natural function of the ground
| involves another point. It acts as one
plate in huge condenser, the antenna
wire acting as the other. This is the
arrangement at the broadcasting sta
ton, and since your receiving set is a
parallel of that in miniature 1t is obvi