N4GG's Spark Gap Transmitter

"Blue Lightning," a fully synchronous 1/2 KW rotary spark gap transmitter circa 1910, completed in 2010 by N4GG. Nearly every piece is from the period or hand made using period materials and processes. There were thousands of these in 1910 (though hardly any two alike), there are only a few in existence today. While correct to 1910 methods and materials, this transmitter was built without plans - each amateur did it "his way" in those days.



Beginning of final assembly. Note the Thordarson Type R spark transformer (circa 1910) being used as a weight to hold the mahogany main chassis in place.


The completed Leyden jar rack. Indian mahogany with 1910 finish, Copper from Georgia Copper, Gainesville, GA. The lower tray is designed to hold one bottle's worth of electrolyte, should a bottle ever rupture.


Mid way through final assembly. The knife switches are period - both are on slate bases. The left switch is a Perkins 250 Amp, circa 1920. The right switch dates to around 1910 - it was used in the lighting panel of a subway station in the NYC IRT subway system. It was obtained as a total basket case and had to be remade from the ground up.



The completed rig. The key is on the other end of ten feet of wire. Some folks prefer to operate it that way!


50 KV peak-to-peak on the Leyden jar capacitors. Today this is referred to as corona - in 1910 they called it "brushing." It wastes power but it sure is fun to see.


The gap running around 1,500 amps, 240 breaks/sec. This is why its called "Blue Lightning." At higher power it should be viewed through a welders mask - the gap's UV output is not eye safe at higher power levels.


The 1/2 KW rotary spark gap transmitter in action