Dear all,
I would like to comment these MF propagation statements by my own
experiences down below:
"John RABSON" <[email protected]> schrieb:
> On 05/07/2007 at 18:06 Roelof Bakker wrote:
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> [ ... ]
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> >500 kHz has great potential; a former spark told me that they used to work
> >PCH at MF from the Straight of Malaysia when HF was not usuable. They used
> >one KW on a large Shell tanker.
Around 1957, when I had been at sea, the average MF transmitter power on
a cargo ship had been around 200 watts, but the ships had rather
efficient inverted L or Tee aerials from mast to mast. Later on these
large aerials were no longer possible due to a more compact ship design
and the wish not to have wire aerials any longer which need to be
removed for loading or unloading. They were replaced by self supporting
verticals about ten meters high. The efficiency of these new aerials, in
spite of fulfilling the so-called ITU "meter ampere" requirement,
revealed to be considerably lower, however, and in the seventies, after
an international measuring campaign, there had been an ITU decision to
increase the "meter ampere figure" for (these new) MF aerials by a
factor of two, with the consequence that transmitter power had to be
increased by a factor of four, to maintain the minimum range requested
by the international maritime safety treaty.
Therefore I would regard a MF QSO from the Malakka Strait to PCH
possible with a combination of an old style MF aerial (feasible on a
large tanker, no need to be removed) and the 1 kW power only, but even
then it is hard to believe for me that this should have been a regular
communication mode, especially because of the large land masses in
between. But I shoud add that I have never been in these waters myself.
> And one of my mentors, who used to be a Sparks, told of when he called an
> Alaskan coast station > on 500 with the standard message saying he was going
> into port and was answered by a station in > New Zealand.
The Pacific, on the other hand, is entirely difficult. It is the largest
sea area on earth, with only a few islands in between. At night on watch
at 500 kHz, it was quite commom in the north Pacific to hear exotic
calls like ZKN, Niue Radio, or ZKR, Rarotonga Radio from the Cook
Islands in the south, to remember only a few. Ships I have met and
looked up in the ITU list of ship stations quite often were equipped
just with MF, but sailed from Australia and New Zealand up to the US and
Canada (and even Alaska as reported). From an old ITU list of 1959 I can
still recall that the powers of ZKN and ZKR at that time were in the
order of 250 to 300 watts.
This shows that MF has been quite dependable at night over at least half
the Pacific. On the other hand it is my feeling that just the fact that
the New Zealand Coast station responded to a QTP message of a ship going
into port in Alaska, that receiving this message across the whole
Pacific might have been regarded a special or rare case by the operator
(or that both operators have met before). In general 500 kHz operators
are rather reluctant or conservative in using the key. 500 kHz has been
a watch and distress frequency and not for chatting.
HW?
73 Ha-Jo, DJ1ZB
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> John F5VLF
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