OT: possible ham operation in the region of 415-526.5 Khz

[Mike Morrow-3]

Ron wrote:

>For emergency use, the famous "Gibson Girl" hand-cranked lifeboat
>transmitter only put out about 5 watts amplitude-modulated CW (MCW) on 500
>kHz and had, under the most ideal conditions, an end fed wire 100 or 200
>feet long (attached to a box kite or balloon). Frequently it was much, much
>shorter, depending upon weather conditions. Such a setup was considered to
>have a working range of up to 200 miles.

>It seems that 600 meter communications using a very short antenna and
>moderate power should be entirely practical over tens of miles in the
>daytime and perhaps hundreds of miles at night.

MF communications in the 410 to 512 kHz band, prior to worldwide abandonment
of maritime Morse in 1999, was fascinating to monitor.  I always kept a
receiver on 500 kHz in my station at night.  It was amazing what could
be heard over very long distances, even when the receiver was hundreds of
miles inland.

The US military's hand-cranked Gibson Girls (SCR-578, later the AN/CRT-3) emergency
600m transmitters were carried in almost every military aircraft that had liferafts.
In Pacific Theater WWII submarine "lifeguard" duty (looking for downed aviators),
the rescue subs always monitored 600m in case a downed aircrewman was using his
Gibson Girl.

There was also a two-way system intended for use by the distressed party in Arctic
rescue efforts, consisting of the SCR-578 transmitter and a dry battery powered
AN/CRR-1 MF receiver.

There was also a large variety of larger maritime lifeboat receiver-transmitter units
(also hand-cranked) like the RCA ET-8053 and MacKay 401-A that transmitted and received
Morse on the 500 kHz (2 watts) and 8364 kHz (5 watts) distress frequencies.  These were
all vacuum tube radios, although late in the maritime Morse era some of these lifeboat
radios introduced some solid state technology.  

The ERP of such 2 watt 500 kHz transmitters under the best of circumstances must had
been well under 100 mW, yet many decades of experience proved these devices to be effective.

My point is that quite a lot of experience and historical importance is attached to very
low power operations in the old maritime MF band.  I'd love to see a part of the band be
allocated world-wide to amateur operations.  I believe that there will be some surprises
at what can be accomplished, especially at night, when/if amateurs start re-discovering
these low MF bands.  Six hundred meters and up, anyone?

Mike / KK5F
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[Johnny Siu]

Again, thanks Ron and all other replies on this topic initated by me.

I have already got in touch with experts in IARU Region 3 on this subject which
would be an agenda item in the coming WRC2012.
 cheers,


Johnny VR2XMC




________________________________
寄件人﹕ Ron D'Eau Claire <[hidden email]>
收件人﹕ [hidden email]
傳送日期﹕ 2010/12/17 (五) 12:20:42 AM
主題： Re: [Elecraft] OT: possible ham operation in the region of 415-526.5 Khz

An interesting footnote for some of the newer Hams:

Historically, the reason 500 kHz was chosen for emergency calling (SOS) was
that such a high frequency was considered of little use for long range
communications. Back before WWI, "everyone knew" long range communications
required lower frequencies and some of the most powerful shore stations
operated at frequencies as low as 17 kHz. The whole plan for disaster
communications at sea was to alert *nearby* ships to provide aid, so a
higher frequency with its shorter range was ideal. All ships subject to
SOLAS (Safety Of Life At Sea) rules were required to carry a calibrated
radio direction finder in the wheel house to "home in" on a 500 kHz signal
to locate a lifeboat or ship in distress.

Along the same thinking, the local AM Broadcast band was put above the 500
kHz frequency - roughly 550 to 1500 kHz - where high power stations would
have a range of perhaps some tens of miles, the experts said, suitable for
bringing newfangled "broadcasting" into local households. And, of course,
those pesky "Amateurs" can have the frequencies above roughly 1500 kHz (200
meters) and will certainly never get out of their own back yards on such
high frequencies.

Fortunately, that was one more time when all the experts were wrong.

Ron AC7AC

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[David Cutter]

Grimeton is planned to be on air Christmas Eve, 24 Dec at 0800 UTC on 17kHz.
http://www.alexander.n.se/transmissions.htm  signing SAQ

I remember being woken at 3am by the 500kHz auto-alarm while off Western
Sahara from an SOS in the English Channel.  So much for short distance !


David
G3UNA

> An interesting footnote for some of the newer Hams:
>
> Historically, the reason 500 kHz was chosen for emergency calling (SOS)
> was
> that such a high frequency was considered of little use for long range
> communications. Back before WWI, "everyone knew" long range communications
> required lower frequencies and some of the most powerful shore stations
> operated at frequencies as low as 17 kHz. The whole plan for disaster
> communications at sea was to alert *nearby* ships to provide aid, so a
> higher frequency with its shorter range was ideal. All ships subject to
> SOLAS (Safety Of Life At Sea) rules were required to carry a calibrated
> radio direction finder in the wheel house to "home in" on a 500 kHz signal
> to locate a lifeboat or ship in distress.
>
> Along the same thinking, the local AM Broadcast band was put above the 500
> kHz frequency - roughly 550 to 1500 kHz - where high power stations would
> have a range of perhaps some tens of miles, the experts said, suitable for
> bringing newfangled "broadcasting" into local households. And, of course,
> those pesky "Amateurs" can have the frequencies above roughly 1500 kHz
> (200
> meters) and will certainly never get out of their own back yards on such
> high frequencies.
>
> Fortunately, that was one more time when all the experts were wrong.
>
> Ron AC7AC
>

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