[InHam] OT Pre-radio morse code history lesson De Emcom Forum w/permission

[Paul Webster]

Hi, This stuff just fasinates me. How they could do so much w/so very little. 
This article tells about the military use of mirrors to send morse code over some pretty un-beleivable distances as late as 30 some years ago. 
Some radio systems can't reach as far as 2 guys on mountain tops did w/mirrors in the 19th century. 
Simply amazing!!
Read & enjoy. 

The Emergency and Survival Non-Radio Communications Course


Emergency and Survival Non-Radio Communications - Part 1.

The Heliograph (The Signal Mirror) - Chapter 1.


>From Wikipedia, the free encyclopedia


A Heliograph (from the Greek Helios meaning "sun", and graphein meaning write)
is a wireless solar telegraph that signals using Morse code flashes of sunlight
reflected by a mirror. The flashes are produced by momentarily pivoting the
mirror, or by interrupting the beam with a shutter. The heliograph was a simple
but highly effective instrument for instantaneous optical communication over 50
km or more in the late 19th and early 20th century. Its major uses were
military, survey and forest protection work. Heliographs were standard issue in
the British and Australian armies until the 1960s, and were used by the
Pakistani army as late as 1975.

The practice of useing the Heliograph for Communications was referred to as
Heliography.


Mance Mark V (British) heliograph

There were many heliograph types. Most heliographs were variants of the British
army Mance Mark V version. It used a mirror with a small sighting hole in the
middle. The sender looked through this hole to align the tip of a sighting rod
with the target. They then aligned the mirror so the small shadow that was the
reflection of the sighting hole was on the tip of the sighting rod. This
indicated that the sunbeam was pointing at the target. The flashes were produced
by a keying mechanism that tilted the mirror up a few degrees at the push of a
lever at the back of the instrument. If the sun was in front of the sender, its
rays were reflected directly from this mirror to the receiving station. If the
sun was behind the sender, the sighting rod was replaced by a second mirror, to
capture the sunlight from the main mirror and reflect it to the receiving
station. The U. S. Signal Corps heliograph mirror did not tilt. In this type,
flashes were produced by a shutter mounted on a second tripod.

The heliograph had some powerful advantages. It allowed long distance
communication without a fixed infrastructure, though it could also be linked to
make a fixed network extending over hundreds of miles, as in the fort-to-fort
network used in the Geronimo campaign. It was highly portable, required no power
source, and was relatively secure since it was invisible to those not near the
axis of operation. However, anyone in the beam with the correct knowledge could
intercept signals without being detected. In the Boer war, where both sides used
heliographs, tubes were sometimes used to decrease the dispersion of the beam.

The distance that heliograph signals could be seen depended on the clarity of
the sky and the size of the mirrors used. A clear line of sight was required,
and since the earth's surface is curved, the highest convenient points were
used. Under ordinary conditions, a flash could be seen 30 miles (48 km) with the
naked eye, and much farther with a telescope. The maximum range was considered
to be 10 miles for each inch of mirror diameter. Mirrors ranged from 1.5 inches
to 12 inches or more. The record distance was established by a detachment of
U.S. signal sergeants by the inter-operation of stations on Mount Ellen, Utah,
and Mount Uncompahgre, Colorado, 183 miles (295 km) apart on Sept 17, 1894, with
US Army Signal Corps heliographs carrying mirrors only 8 inches square.

In the Civil Air Patrol mirrors are still used by the SAR ground teams to
attract the attention of our search aircraft.

I recommend that everyone have several signal mirrors.
A small mirror could easily save a life.

More Information is given on Wikipedia under Heliograph.

I suggest Googleing "Heliograph".


Ralph G. Rogers

The preseding was copied & pasted from the Emcom Forum to this email w/permission & even encouragement from Ralph Rogers, who owns the Emcom Forum that I just joined. 


73/75 de ka9jwx, Paul Lewis Webster
SKCC #5322
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