New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1922-08-06
Reflected w ave
Employed as
Lighthouse
Short Wave Radio Revolving
Reflector Used to Warn
Ships of Danger When
Near Rocky Coast in Fog
Experiments in Scotland
System Devised by Marconi
and Assistants Promises
to End Last Danger at Sea

The first wireless lighthouse has
been erected of the east coast of Scot.
land, on the island of Inchkeith, and
its operation during the experimental
period indicates that 1t will remove one
of the last terrors from navigation. Ii
is designed on the principle of reflected
waves outlined by Guglielmo Marconi
before the Institute of Radio Engi-
neers recently. The exception Is that
the reflector revolves In the same man
ner as the reflector of an ordinary
lighthouse.
When it Is universally adopted the
system will act as a warning to ships
in foggy weather when they are near a
dangerous coast, while in normal times
It Is as accurate as the radio com
pass In giving ship its bearing. The
working of the system is described in
paper read by G. S. Franklin, before
The Wireless Society Of London.
THE general idea is that trans
nitter and refectox revolving will act
as kind Of wireless lighthouse. It is
not intended at present for long ranges
but rather that revolving refectors
should be erected In position, similar
to those at present occupied by fog
signals and be capable of similar
ranges SO as to give the position Ia
ships during fog when within about
ten miles of the danger point.
Four-Meter Wave Used
AN experimental revolving re
Hector was erected on Inchkeith, and
tests were made to the steamship Pharos
with a 4-meter wave, spark trans
mitter. a reflector of meters aper-
-ture and single valve receiver OH the
ship, working range Of seven nautical
miles was obtained. The reflector
made a complete revolution once every
two minutes, and a distinctive signal
was sent every half point Of the com
pass. 1t was found that this enabled
the bearing of the transmitter to be
determined within u point Of the
compass, or within 2.s degrees.
These results were good, but 1t was
desired to know the effect of putting
the transmitter lower down at the point
quite near. A new and larger reflector
was designed, and erection has just
been completed.
"The best method Of giving the d.
rection to ship by means Of such a
revolving beam required consideration
The method being adopted is, the
author thinks, the most practical one
When listening in receiver to a
moderately sharp revolving beam the
signals are heard only for very short
time. Taking the case of such beam
as produced by, the 42s meter wave:
supposing 1t makes complete revolu-
n mi af
with the receiver at maximum sensi-
tiveness signals will be heard for seven
seconds every minute. Near the limit
of range signals will be heard for
only about four seconds. The exact
time of maximum signals il not easy
TO determine by ear, but the times of
starting and vanishing are easy to de-
termine, as the rate Of rise and fall of
the signals is extremely rapid. The
time halfway between these two times
gives with great exactness the moment
when the beam is pointing to the ship
Method Has Disadvantages
''It would be quite possible to send
a general broadcast signal when the
beam passes through true north; then
, by arranging for the beam to revolve
at a perfectly uniform rate, the bear
ing on the ship could easily be de-
termined by means of stop watch
This method is probably the most &C
curate, but has some disadvantages
It entails accurate timing mechanism
and three, or perhaps four, receivers
on the ship, as well as the use of 8
stop watch.
"For the short wave two receivers
are required, one at each end of the
bridge or one fore and one aft. This
is necessary to avoid screening by the
ship itself. If the broadcast wave for
giving the time when the beam passes
true north is another short wave, then
two more receivers would be required,
"The method Professionally adopted
avoids accurate timing mechanism. On
the base of the revolving reflector
contact-segments are arranged so that
definite signal is transmitted every
half or quarter point of the compass.
A distinctive letter is sent every two
points and short signs mark the inter
mediate points and half points. When
listening in at the receiver a few short
signs are heard and one or two letters.
If the letters T, l, o., I, T, / are
heard.
'The halfway position is between
South and S. II West, and the bear
ing to the transmitter will be S. Il w.
"The apparatus proposed is of q
very reliable nature. The spark trans
mitters are very robust and last for
years without attention. The receiv-
ers are simple valve rectifers with
fixed adjustments except for "back-
ing off" potentiometer for dealing with
powerful signals at close range. The
attenuation of these waves over sea
is SO strong that little experience
enables distance to be judged by
strength of signals, and this can be
measured by means of the poten-
tiometer. The only qualification nee
essary for person determining the
bearing is the ability to read a few
Morse signs"