Right. What is being transmitted is an electromagnetic field, NOT a
sound field. Sound is AIR (or water) vibrating. Sound waves travel a bit
faster than a foot per msec. Sonar uses sound. The system Mike is
talking about is radio.
Radio is an electromagnetic field, which the simultaneous existence of
an electric field and a magnetic field at right angles to each other,
and they move through space at the speed of light. We can't hear radio
waves, but we could hear high frequency sound waves if the radio waves
were somehow detected (the trusty non-linear junction) and caused
something to vibrate (or even to arc).
73, Jim K9YC
On Thu,3/23/2017 3:03 PM, Mike Morrow wrote:
I didn't understand the reference to audio either.
When I on the crew of a US ballistic missile submarine more than 40 years ago,
our main communications receivers were AN/BRR-3 units whose full frequency
range was only 14 to 30 kHz. These received signals from coastal stations
operating at megawatt output levels, but there was no one near such a station
with his ear drums damaged by or even sensitive to the station's continuous
output.:-)
Anyone can listen to such signals as they exist today.
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