[Boatanchors] Aircraft carrier radio operations

[William L Howard]

I was recently asked why the Japanese navy would use Long Wave
transmissions for their aircraft returning to their carriers. Checking
the internet via Google, I found that:"Longwave" refers to all
frequencies below the lower end of the AM broadcasting band at 540 kHz.
The lower limit of what frequencies constitute "radio" is not precisely
defined, but 5 kHz is a widely accepted starting point for the radio
spectrum.For many years, radio hobbyists ignored longwave because most
commonly
available communications receivers only tuned down to 540 kHz.
However,most new receivers today tune down to at least 150 kHz and
longwave DXing is enjoy new popularity.

One big problem when tuning longwave is electrical noise from power
lines, electrical devices, motors, etc. Longwave is far more susceptible
to such noise than higher frequencies, and you might hear only a loud
"buzz" when you tune across longwave from your location. Also, static
crashes from thunderstorms can be severe, especially in summer. To
combat noise, many longwave DXers use an indoor "loop" antenna that
allows rejection of nearby electrical noise sources. Other longwave
DXers use special phasing units to reduce noise levels.

Reception distance on longwave is similar to that on the AM broadcast
band, as are reception patterns. Greater range is possible when the
signal is reaching you over a water path, as is often the case in
coastal regions. At night, reception of stations from hundreds or even
thousands of miles away is possible. Night reception on longwave is
better in winter than in summer, and the equinoxes often give the best
propagation.

Unlike the short-wave frequencies above 1700 kHz, the longwave spectrum
is allocated on a more "ad hoc" basis, with different users and services
frequently sharing the same frequency range. Here is a general
description of the world below 540 kHz:

Below 155 kHz: Signals below 155 kHz don't propagate very well via the
ionosphere; the absorption is too great even at night during
winter.These signals can travel for thousands of miles via ground wave,
but high transmitter powers are required. Signals at very low
frequencies,
about 50 kHz and lower, can penetrate sea water very well. As a result,
these frequencies are used by military forces of the major powers,
especially for communication with submarines. The U.S. Navy's "Omega"
navigation system is found on 10.2, 12, and 13.6 kHz. The Russian navy
operates a similar system on 15.62 kHz. The U.S. Air Force has a
FSK-based communications system on 29.5 and 37.2 kHz. This system was
established to provide a backup in case nuclear explosions rendered the
ionosphere useless for propagation. Miscellaneous FSK-based stations are
found here for direct communications with submarines and naval forces.
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Now my question is: Can anyone confirm the use of Long Wave by the
Japanese navy?

Did the US Navy of WW II use the same sort of transmissions?

Bill Howard