NMO - Part 3 - Why 500 kcs?


Copyright 1994 
by Jeffrey Herman
All rights reserved

Part 3.  Why 500 kc/600 meters?

I have researched the literature in order to find an answer to this
question, but have found nothing. I tend to think that this particular
wavelength, 600 meters, became the standard by accident rather than 
some body of policy-makers deciding that it was to become the worldwide 
calling & distress frequency. Maybe the nature of early equipment might 
be the reason this wavelength became the standard; the length of the 
antenna on some early transmitters dictated the center frequency of 
their very broadband signal - given that the antenna would run the 
length of the ship might have a bearing on 600 meters became the 
international CW wavelength.

Regardless of whether it was by accident or choice, what was handed 
down to us was a wavelength with excellent evening propagation. 
Starting at about 2100 local 500 would come alive. Any ship or shore 
station within 3000-4000 could be heard by an excellent combination of 
ground wave and sky wave - nothing was missed within this radius! Shore 
stations of more than 5000 miles were easily copied (Australia and New 
Zealand boomed in nightly).

Daytime propagation consisted of only ground wave: 300-500 miles
was the maximum range possible. Thus most daytime traffic was passed
on the HF channels.

The idea of combining a distress frequency and a calling frequency was
an excellent one - it insured no distress calls would be missed, and
at the same time everyone knew where everyone else was at! No need 
searching various frequencies looking for a particular ship or shore-
station. The result was a worldwide partyline; if you sent so much as
a single dit everyone would hear it:

Ships operated on either a one-op or two-op schedule so our broadcasts
coincided with these skeds. But shore stations had to remain on the
air 24 hours a day. Late nights could become a bit of a bore for some
shore ops, heavy eyelids and such. So out of boredom (or maybe by
``accident'') a single dit would ring across the Pacific, only to
be answered by another dit possibly several thousands of miles away.
Then all hell would break loose: every shore station and any ships
with an on-duty op would be sending dits! For several seconds 500
sounded as if 100 or more carriers were ditting away. As quickly 
as it started it would fade away.

A variation of this was someone sending a single GE (good evening);
of course it would be impolite not to respond in kind so someone
else would answer with GE. Within a half second at least one hundred
GE's would flood the frequency! My log entry would look like this:

GE / GE / GE / GE / (OPNOTE: AT LEAST 100 GE'S SENT)   500   1123Z

Some Coasties were unhappy with their duty assignment (Alaska, or
some LORAN station in the middle of the Pacific, or on board
a patrol ship) and made their sentiments known to the world:
one op would send an F, a second disgruntled Coast Guardsman
would follow with a T, only to be followed by by a third
CG op sending G - three Coasties separated by 100's or 1000's
of miles of water expressing their thoughts as one. The acronym
FTG stood for a very common expression in the Guard: F___ The Guard.
In the log it goes:

FTG                                                    500    1305Z

Needless to say, the CO (commanding officer) (`The Old Man') of NMO, 
upon reviewing the log the following day, would attach a nasty note 
expressing his displeasure at seeing such entry in an Official U.S. 
Government Legal Document blah, blah, blah... The Chiefs on the other 
hand would give out a hardy laugh and express their delight that this 
acronym was still traveling the airwaves.

After 2100 local there would be a steady stream of CW on 500 - ships
calling shore stations or other ships:

KOK KOK KOK KOK KOK KOK KOK KOK KOK KOK (making a pest of himself!)
DE   (in other words: `who the heck is calling me?')
DE KNLS TR K
KNLS DE KOK R UP 485 K
OK 485/480 UP
EE
EE

Translation: The ship KNLS, ignoring the usual 3X3 callsign format 
instead was going to endlessly call the shore station KOK until he
got some attention; KOK interrupted him with a simple DE after which
KNLS told him he had a travel report (TR). KOK's answer was `Roger,
I'll transmit on 485 kc' to which the ship answered `Okay, you 
transmit on 485 and I'll transmit on 480 - let's go up' (up in
wavelength that is, not in frequency - traditions are hard to
break!). By the way, KOK was a shore station located on a
beach here on Oahu.

Or,

TTT TTT TTT CQ DE ZLD ZLD CYCLONE WARNING NR 15 QSW 428 AR

(These types of broadcasts, prefaced with TTT or XXX, will
be discussed in Part 4.)

Or,

CQ CQ CQ DE WNOP WNOP ANY ONE HV 2100Z SOUTH PACIFIC WX? K
WNOP DE XSU GE WILL GIVE 2100 WX ON OUR 2200 BCST K
OK TKS OM SU
SEEU
EE
EE

and on and on throughout the night - very orderly. You'll note each
series of transmissions end with a `dit dit' (recorded as EE); and
amateur radio operators thought they invented this `prosign'!

Part 7 will contain an actual transcription of one of my evening logs.
Part 6 will described a distress in which a ship broke up in heavy seas
and all hands were lost - it will contain my QSO with the ship's 
operator up to the last second of his life.


End of Part 3.

Jeffrey Herman KH2PZ / KH6
jeffreyh@hawaii.edu