update 20 Aug 2020
you had access to a radio antenna that would enable you to
tune in signals from the past.
my contention for some time now that cold silent radios have
little attraction to the casual museum visitor.
Technology Museum installation amounts to cable
radio. A good broad-band antenna above the building
low-, medium-, and high-frequency signals that are boosted
distribution amplifier, and routed to radios throughout the
75-ohm coaxial cable. Our local oldies station, 1080 -
feeds the amp, and provides appropriate vintage programs
from a CD or
MP3 player that are not available out of the æther. We
have a number of interesting receivers on the air via this
what about signals from the past?
started to study Edwin Howard Armstrong's early experiments
it became apparent that it would be interesting to hear what
he heard when he
discovered regeneration. He describes tuning in the
Marconi press station on Cape Cod, MCC, and how the volume
and then the timbre of the
sound changed when he adjusted the tuned circuit he had
added to the"wing" of of Deforest's Audion
receiver. We all think
we know how a regenerative receiver sounds. You get a
whooping beat note as you tune past each AM carrier on the
The problem is MCC was a spark station, there was no
carrier, and there's hardly anyone alive who has actually
heard spark on the air
through a regen.
born the MCC simulator. A 120 hertz square wave was
used to excite a parallel tuned circuit at about 800
KHz. This produced
trains of damped waves with a "spark rate" of 240 hertz, the
reported sound of MCC. Output was about a microwatt,
which represents a
pretty strong signal when applied directly to the antenna
terminal of even a primitive receiver. The transmitter
was keyed by a Morse
signal generated by a personal computer to make the original
enough it was just like Howard said:
old timers remember CC, later known as MCC and WCC, the
Marconi press station at Wellfleet, Mass. This station
one-hundred percent reliable testing standby of all
experimenters, andon MCC the first tests were made. A
standard audion detector system was
set up and tuned in, and a tuning inductance introduced into
the plate circuit of the audion.
things began to happen. As the plate inductance was
increased, the signals were boosted in strength to an
unbelievable for those days, the more inductance the louder
the signal,until suddenly the characteristic tone of M. C.
C. -- the tone which
any of the old timers, if they heard it on Judgment
Morn, would recognize instantly -- disappeared, and in its
place was a loud hissing
tone, undeniably the same station, but recognizable only by
the characteristic swing and the messages transmitted.
slight reduction of the plate Inductance and the old tone
was back again, -- and then the placing of the hand near a
tuning condenser, and
the hissing tone reappeared.
no particular mental effort to realize that here was a
fundamentally new phenomenon, as obscure as the principle of
operation of the audion itself, but which opened up an
entirely new field of practical operation.”
phenomenon was RF oscillation.
the only image I found of Armstrong's original hookup.
However, I believe this is something that was sent up as a
demo, using equipment from the Columbia lab, some time after
the original discovery. However, tracing the wires gives
us the schematic on the right. So I built one.
and hear it HERE
demonstrations of his receiver in the Winter of 1913-14
revealed that the regenerative receiver was not only the
best receiver available for
spark radio telegraphy, but also worked extremely well
on continuous-wave Morse signals. So there were three
signals to be heard, buzzing spark, on-off keyed CW from the
high-frequency alternators, and frequency-shift keyed CW
Poulsen arc stations. During a demonstration to
representatives from AT&T their chief engineer observed
that the latter sounded
like "an inebriated flute player."
simulated MCC spark transmitter has been joined by the
Cliften, Ireland Marconi spark station, the Nauen,
Germany,Slaby-Arco alternator and the San Francisco, Federal
Arc. The three devices are on different frequencies,
and their signals are combined so that the demonstration
receiver can be tuned
across the band as it sounded in 1914. Thus, Virtual
Æther has been attained.
is keyed by a separate Arduino micro-controllerboard.
The text used has been derived from the signals recorded
by David Sarnoff in his report to Marconi America following
the January1914 demonstration at Belmar, NJ, the location of
our Radio Technology Museum.
Latest Virtual Æther Video
1940 U.S Navy type RAX Receiver
needed something relatively simple, so museum visitors could
operate it themselves.)
Experimental Armstrong Kiosk content
- including more videos.
Radio Technology Museum website.