Visit the #1
Marconi Page in the USA...
Guglielmo Marconi after showing much
interest in becoming an early entrepreneur combined these two units
of classroom interest for his earliest experiments in wireless signaling. His
first effort of major consequence and his earliest significant effort was to set
up a transmitter and receiver at his home. He placed the receiver several
thousand feet up in back of his property while his brother stood ready with a
shotgun to signal back that he was hearing 3 dots or the Morse letter
'S'.. This happened almost immediately and Marconi was off to make many
improvements until his apparatus was several miles apart and still working and
improving all the time... He eventually received capital to work
with and commenced building a high powered transmitter site in Clifden, Ireland.
This spark transmitter was measured in thousands of watts and was located so as
to have an optimal path across the Atlantic Ocean to where he eventually sent a
series of letter 'S' to be copied beyond the horizon and to ships at sea along
the route to America.
The undersea telegraph cable people became nervous when it
was apparent that Marconi was going to be bridging the Atlantic any day. His
worked continued until he had built a very successful business and with it much
work in such
places like Cape Cod, Massachuestts which became his 'laboratory' and proving
ground. Soon he set up wireless station 'SC' in Siasconset on Nantucket
and station 'CC' in Wellfleet, Massachusetts. The age of maritime radio
communications was off and running. Serving him then as a new operator on Nantucket
was a young David Sarnoff. Marconi soon made him #1 sidekick and there is the
embryo of RCA, NBC in this country. Marconi Ltd. was the fastest rising
star in the communications business of the day and he would live to see many
improvements but not to the un-imaginable wireless communications industry of
today...
Marconi probably did more than
anyone to spark the leading edge growth of RF communications. He also
demonstrated a 'Bill Gates' like attitude and with the love of his craft
propelled him to aspire way beyond the 'college graduates' of the day...
A true Radio Hero... he is the Real father of radio...
He will be remembered at the
top of the radio inventors list forever...
"One thing all of the great men share in common ....
They believe in what they are doing and they NEVER GIVE UP"
It was a German mechanic who invented Ruhmkorff's
coil, a type of induction device that could produce sparks more than 1 foot (30 centimetres) in length. This coil was used
as the first radio transmitter along with some other primitive electrical
devices. The electrical researcher Heinrich D. Ruhmkorff was born in
Hannover, Germany. After apprenticeship to a German mechanic, Ruhmkorff worked in England with Joseph
Brahmah, inventor of the hydraulic press. In 1855 he opened his own shop in Paris, which became widely known for the production of high-quality electrical apparatus. There he built a number of improved induction coils, including one in 1851 that was awarded a 50,000-franc prize in 1858 by Emperor
Napoleon III as the most
important discovery in the application of electricity. He was able to improve Callan's two-winding induction spark-coils, on the basis of the research conducted in Paris by Masson and Breguet in 1842, in such a way that since then these devices bear his name. Ruhmkorff's coil could produce sparks more than 1 foot (30
centimetres) in length. Ruhmkorff's coils, which produced high-voltage current within a secondary armature winding, were used for the operation of Geissler and Crookes tubes as well as for detonating devices.
Ruhmkorff coil was popular for energizing discharge tubes and in particular for generating x-rays (which were discovered in 1895 by Roentgen). Ruhmkorff's doubly wound induction coil later evolved into the alternating-current transformer. He also invented a thermo-electric battery in 1844.
This
early induction coil device became Marconi's basic 'spark' transmitter and also
the source for 'spark plug' energy in the later to be invented internal
combustion engine.
The Coherer is the result of the work of many men -
Hughes, Lodge, Branley and Popoff among others - consists essentially of a small
quantity of metal filings lying loosely between metallic electrodes. The first
practical form of the device for telegraphic purposes was brought out by
Marconi. and consisted of a very small quantity of nickel filings, to which were
added a small percentage of silver filings, lying between silver electrodes
having beveled ends so that the space between them, in which were the filings,
was wedge-shaped. The
purpose of thus beveling the plugs is to enable the sensitiveness of the coherer
to be adjusted. The most sensitive position is when the nose of the wedge is
pointing downward and reverse position is that of least sensitiveness. The plugs
and fillings are enclosed in a glass tube, which is exhausted to a partial
vacuum, and 
the wires connected to the plugs pass out through the ends of the
tube (fig.41). The
coherer depends for its action on the fact that, if its terminals are subjected
to a potential difference above a certain value, the resistance due to the loose
contact between the fillings and plugs suddenly falls to a much lower value;
some investigators think that ordinary electro-static attraction is a sufficient
explanation of its behavior, others hold that microscopic sparks pass between
the fillings and slightly weld them together; however this may be, the fact
remains that, after being subjected to potential differences set up by the
oscillations, the 
resistance falls enormously, and if the coherer is joined up
with a relay and cell, and the relay contacts joined up with a Morse writer and
battery, the passage of electrical oscillations will be made evident by the
closing of the relay circuit and consequent recording of signals.
This
is the first known electrical 'detector' and was the basis for Marconi's first
receiver...
Here is an early diagram of a basic coherer receiver
complete showing antenna induction coil, sensitive relay, battery and ringer
which caused a reset of the filings inside the coherer once the detector
was 'set'... This first receiver was actually a 'digital' receiver as once the
level to the relay was brought high it then became necessary for a
mechanical reset to cause the filings to go 'random' and wait for the next radio
frequency 'RF' signal. If the signal was a long dash, then the ringer
would stay ON until there was no incoming signal...