[Lowfer] spark fm transmitter

[james fisher]

spark fm will work. spark am was tried about 1909 and
voice and music were heard in the northeast from a
spark transmitter that used a very high spark
frequency rate generated by using a 25 khz power
source. Under these conditions it was possible to
generate a nearly continuous carrier. am was generated
by using 20 carbon button microphones in the tank
circut to modulate the carrier. the only drawback is
that it took loud sounds to modulate without using an
amplifier and there was a tendency for large sparks to
jump from the carbon mikes to the person talking. it
also burned out the carbon microphones quickly. the am
signal still had the drawbacks of spark in that it
used up a very wide bandwidth, but this should be easy
to fix at microwave frequencies with cavity filters

73
kd6iwd

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