Evening star., 1922-05-16
REVISING RULES
TO protect RADIO
Bureau Of Standards Takes
Steps to Prevent Fires From
Crossed Antennae.

A tentative revision of the national
electrical fire code, containing in
stallation rules to prevent fires from,
lightning and crossed antennae
wires. has been made by the radio
laboratory of the bureau of stand
ards. The revision, as now published,
tosetner with ampiifications later to
De determined, will be made perma-
nemt after September l.
me principal provisions already.
are IN erect, and failure to observe
them may result in loss Of insurance.
Main Features Of Revision.
Some Of the main features of the
revised rules follow:
Ahtennae outside of buildings shall
NOT cross over or under electric light
than 500 volts or railway trolley or
Ieeder wires, nor shall it be so To-
Gated that a failure of either anten-
nae or OF the above mentioned cleo
tric light or power wires can result
IN contact between the antennae
er~wires
Antennae shall be constructed and
installed in a strong and durable
manner and shall be SO located as
70 prevent accidental contact with
llgh. sst n and power wires by sagging or
splices and joints in the antennae
span. unless made with approved
clamps or splicing devices, shall be
soldered. ~
Lead-in wires shall be of copper,
approved copper-clad steel or other
approved metal which will not cor
rode excessively, and in no case shall
they be smaller than No. IA B. &
$: gauge except that approved copper
clad steel not less than No. II B. & s.
may be used
Lead-in wires on the outside of
buildings shall not come nearer than
four inches to electric light and
power wires unless separated there
from by continuous and firmly fixed
non-conductor that will maintain per-
manent separation. The non-con-
ductor shall be in addition to any in
sulation on the wire.
Lead-in wires shall enter the build
ing through a non-combustible non
absorptiVe insulating bushing.
The protective device shall be an
approved lightning arrester, which
will operate potential of 500 volts
or less.
The ground wire may be bare or in
sulated and shall be of copper or ap-
proved copper-clad steel. Preference
shall be given to water piping. Gas
piping shall not be used for ground
ing protective devices.
The ground wire shall be protected
against mechanical injury. An ap-
proved ground clamp shall be used
wherever the ground wire is con-
nected to pipes or piping.
Wires inside buildings shall be Sc.
curely fastened in a workmanlike
manner and shall not come nearer
than two inches. to any electric light
or power wires unless separated there
from by some continuous and firmly
fixed non-conductor making a perma-
nent separation. This non-conductor
sulation on the wire. Porcelain tub
ing or approved flexible tubing may
be used for sncasing wires to comply
with this rule.
At transmitting stations. when the
current supply is obtained directly
from street mains. the circuit shall be
installed in approved metal conduit,
armored cable or metal raceways. II
lead-covered wire Is used. 1t shall be
protected throughout its length in ap-
proved metal conduit or metal race
ways.
It iss desirable that electrical con-
struction companies install radio an
tennae and apparatus for persons who
are not familiar with electric wir-
ing. ~
Antennae Material.
The size and material Of which the
antenna is made should depend. to
some extent, upon the length of the
span which the antenna must bridge.
1t is suggested that for the ordinary
receiving antenna, about 100 feet
long. No. -, B. & s. gauge. soft drawn
copper wire. can be safely used.
The reQuirernents for q protective
device to be connected between the
antenna and ground terminals Of the
receiving set IL for ,the purpose Of
carrying lightning discharges or less
violent discharges caused by induc-
ton or by atmospheric electricity to
the ground, with a minimum chance
Of damage to the receiving apparatus,
building or operator.
Lightning arresters may be used
inside the building, and in such case
they will receive better protection
from moisture and mechanical injury
than lightning arresters placed on
the outside Of building wall.