Radio and Telegraph Accessories
Before Vacuum Tubes
Click on photo for larger picture.
This is a Marconi Transformer. The Copper Strap is all
one piece and the turns on the inner coil count up to
about 100.
It is my guess that this is one of the first
transformers used to inductively couple a spark gap transmitter
to an antenna. Early on in the world of transmitting
Marconi's spark gap transmitter oscillator circuits
were all directly coupled to the antenna and ground.
This caused significant losses.
Ferdinand Braun developed the inductively
coupled transmitter (the antenna and ground circuit
being separated from the spark gap circuit) in his
early experiments with transmission in water. This led
to later experiments in free air transmission which
were quite successful.
Please e-mail me if you have further information.
Circa 1865
- The capacitor in the wooden base charges.
- The coil "charges", that is to say it's magnetic field expands.
- The "points" open (pulled open by the iron bar in the center of the coil) cutting off power to the capacitor and coil.
- The magnetic field starts to collapse the capacitor releases it's energy in an attempt to sustain the coils field.
- The capacitor drains and the voltage induced in the coil by the collapsing magnetic field rises until sufficient to arc across the gap set by the arms mounted above the coil.
- As the energy drains the points close again starting the cycle over.
Acid battery called a Grenet Jar
Circa 1860
A Philips "B" Battery Eliminator 1926 to 1929
