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Early Wireless Transmitters


The wireless telegraph is not difficult to understand.
The ordinary telegraph is like a very long cat.
You pull the tail in New York, and it meows in Los Angeles.
The wireless is the same, only without the cat.
- Albert Einstein

Hertz Resonator

At left is a very rare specimen of one of the devices used in the earliest experiments with "Hertzian waves". This model was used for early demonstrations around the end of the 19th century. 

At about that time there was a significant problem of interference between signals coming from different sources, due to the increasing number of transmitting stations.   Guglielmo Marconi was the first to adopt a tuning system of this type. It's essentially composed of a tesla type high frequency transformer, whose primary circuit is connected to a leyden jar,  forming a resonant circuit which reduces the bandwidth of the signal to be transmitted coming from an induction coil. The signal then goes to the central coil (secondary circuit) whose terminals are connected to the transmitting aerial the earth circuit, to be sent into the space.

A similar tuning circuit, mounted inside the receiver, ensures the reception only of the signal coming from that transmitting station, ignoring all other signals present in the aerial. This circuit has been called a "JIGGER" by Marconi, and was patented in April 1900.


Parabolic Transmitter and Receiver
Utilizing Righi spark gap and Branly Coherer
I believe this is to be a replica made in the 1920's of a very early Marconi experimental set built in the 1890's.

Bing Coherer/Decoherer (receiver)
with Rhumkorff Transmitter

Antenna coupling coils from
Spark Gap Transmitter

Collins Wireless Telephone
(Inductive Model)

A. Frederick Collins was one of the earliest promoters of the of wireless telephone.  Controversy remains as to whether his devices actually worked as promised. Both a transmitter and a receiver, the unit above is the last known Collins Wireless telephone. It is on display at the American Museum of Radio in Bellingham, Wa.

Click here to learn more about Collins and his amazing telephone.


Early experimental Hertz transmitting apparatus
For more information about Heinrich Hertz and his discovery of radio waves, click HERE.

Hertz resonator for detecting Hertzian waves

This simple spark gap apparatus was the first device ever built to detect radio waves.

Righi detector

Professor Righi of Bologna improved the Hertz resonator by replacing the small spark gap with thin bands of quicksilver, as used for mirrors, divided in half by cross lines lightly traced with a diamond. 

Early Spark Gap Apparatus

Max Kohl Spark Transmitter (Bose design) and Coherer Receiver

WT Forward Spark Transmitter


AWA "Jigger"
Helical Transformer

Leyden Jars from Spark Gap Transmitter

Air Chokes from Spark Gap Transmitter

Westinghouse GN4 Avionics Alternator & Transmitter
Signal Corps type SCR73
This unit was mounted under the wing of the aircraft so that air motion rotated the propeller.

Partially dismantled damped wave airplane radio telegraph transmitting set with synchronous rotary spark gap.  From left to right, the self-excited alternator, spark gap, power transformer and oscillation transformer are integrally mounted and enclosed by the micarta streamline casing seen at the right.  Extra rotary electrodes for the spark gap for changing the spark frequency are seen at the extreme left.  Signal Corps set type SCR73.


Connecticut T&E
U.S. Army BC-15A

First transmitter (spark gap) designed for aircraft, designed for use in aircraft. Used in WWI.

Homebrew Spark Gap Transmitter

AWA Spark Gap and Coil

Rotary Spark Gap


Thordarson Flexible 1KW Spark Transformer


"Singing Condenser"

This rare device consists of a primitive carbon microphone,  an induction coil and a condenser. It roused great curiosity in the early days of the telephone because the sounds came from a flat condenser made of sheets of tin and paper.  The famous Italian physicist Augusto Righi explained that every charge and discharge of the condenser produces a changing of density of the air on the frameworks surface, producing sound waves. Today, the same technology is used in the production of high quality electrostatic loudspeakers.

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