New-York tribune., 1922-04-09
Vacuum Gaps
Best Lightning
Protection
Automatic Devices Passed
by National Board of
Fire Underwriters Better
Than Lightning Switches
Are Automatic in Action
Remove Fire Hazard. Protect
instrument; Wires Must
Be Kept 5 Inches Clear

Tiara is q great deal OF misappre-
,.;or as to the best manner in which
:. ,rotect radio receiving set and the
h.,,s in which it is installed from the
.sects Of lightning, and also doubt as
% the exact terms Of the conditions
lid down by the insurance companies.
n ;s nv plan in this article to cover
these points thoroughly and at the same
,;n,o describe the best manner in which
N obtain an efficient ground for the re-
eeiving set Previous articles in this
s.c.ion have described the manner in
mich TO erect al aerial and also how
n construct loop aerial for indoor
reception
The fire underwriters regulations
-eouire the installation of lightning
switch. or protective device. where out
door aerials are erected. The approved
.vpe of lightning switch is single pole
doub,e throw, 600 volt, 100 ampere
tnife switch mounted on a composition
bsse. There is not the slightest doubt
This requirement will shortly be aban-
icued althogether. as it is out of date.
Where only receiving apparatus is
beng used, lightning protection may be
obtained by the use of q vacuum gap
ryOtnC.lNp GeNltt. w ilitIl lidS uGc0 passed
by the National Board OF Fire Under
writer's This device should be in
stalled in place Of the lightning switch
and should be permanently connected
to both antenna and ground wires.
Must he On Outside of House
The regulations require that where
lightning switches are used for protec-
tive purposes they shall be mounted
OF the outside of building and that tho
ground connection shall be made to an
ron pipe driven several feet into the
ground This connection should be
made with weatherproof copper wire Of
No. B. & S. guagc or larger. The
antenna and ground connections shall
he more than five inches away from the
building where the appara tus is in
cta.'cd
ti.hough the single pole switch de-
,~r bed above will amply protect the
OF, Sc on which the aerial is erected. it
ILL., cf course, only function in the
.vcA. the owner has remembered to
'nrsw the switch over into the ground
o. ten when he has finished using
l. receiving set. In other words. the
bl,an element intervenes in this type
/ protective device and it is by no
mesus automatic.
The various vacuum gap srresters,
nich have been designed for lightning
nroccton and which have been passed
loon by the Board of Underwriters,
..e undoubtedly the best for the mod
"TH radio far, who is Il novice at the
art and has only Joined the ranks of
ado enthusiasts since the advent of
broadcasted music. In fact, I am alb
solutely convinced that under the new
equations about to be promulgated
the installation Of vacuum gap ar
lester will bo made imperative.
They arc the best because they are
absolutely automatic in their opera
ilo and always protect both the house
and the apparatus installed within it,
and do not need personal attention in
the form of throwing switch before
they will operate
lightning has the peculiar character
lstc of seeking the nearest path to
tne ground and will readily jump small
air gap rather than traverse the
lengthy metallic circuits used in wire
less. The protective devices are de-
signed upon this characteristic and so
arranged that the feeble radio cur
rents, which cannot pass over the gap,
VIII so through the receiving apparatus
and be properly recorded in the tele-
phone receivers. In this manner the
automatic features of the protective
devices are obtained.
Like the lightning switch the pro-
tective devices must be mounted on
the outside of the building and in their
case, too. the wires must be fastened
at least five inches clear of the build
ing. This can be done with suitable
lnsulators fastened on bolts.
Ground Connection on Iron Pipe
The ground for the lightning switch
and the protective devices can be OBJ
tanned OH any water drain pipe, which
goes INTO the ground on the outside of
the house, or else it can be obtained
oy means of driving an iron pipe sew
efai feet into sofe moist earth. 1t is
good plan to dig hole in soft earth
ana and then drive the pipe into it. When
hillng the hole III it is advisable to do
SO with mixture Of earth and salt
and pack it we'll around the pipe. The
connecting wire to this pipe must be
securely soidered.
AS soon as the aerial and outside
ground have been attached to the
proper terminals Of the protective de-
Vice, or to the terminals of the light
ninng switch, everything is ready to
'S /" 4edu III from tho acfldl TO lne
receiving apparatus. This is done by
means of connecting an insulated wire
10 the same terminal where the aerial
IS joined TO the device or switch The
insulated wire should then be led into
the house through porcelain tube in
Suiator or any Of the specially designed
Ieadng-ln insulators.
Inc iead-in wire is then attached to
.he terminal of the apparatus marked
AERIAL 1t must not be forgotten that
'ne apparatus still needs ground con-
hection to operate satisfactorily. For
mis- purpose the best ground is OBJ
'a'ned by soldering wire to the water
plpe system in the house or to the rad
iator system, but the former is pref
cradle.
The ground connection can be best
made to the water pipe by means of a
ground clamp, which will securely an
cnor the wire to the pipe. The whole
thing should then be properly soldered
70 the pipe. Before attaching the
clamp or the wire, however, it is very
important that the pipe be thoroughly
and carefully scraped so that all dirt,
PANT or corrosion is removed and r
,iean metallic patch left for the con-
lection.
The Importance of this cannot be
especially where
'aeuum tube receiving set is being
lsed. The reason is that a dirty con
'cction viii materially reduce the efii-
'iency of the set, and it will also-ln