The Marconi "S" story is indeed a bit mysterious.
Couple of points:
The Marconi group believed the wavelength was 300m ie 1 mHz. Belrose has
calculated the natural resonance of the tx ant at 817kHz.
The actual detector (coherer, diode?) used at Newfoundland is not known, but
apparently 500ft of wire was lifted by kite from a hill top overlooking the
sea.
This would make a sloping wire at an angle to the sea, giving half a V
against a groundplane.
This antenna would have some directional gain even at mf.
Apart from any antenna resonance the rx was aperiodic.
Signals from England were alleged to have been received at around 1500
Newfoundland local time.
I do not know if any one has done computer modelling of the situation.
It would be possible to make a retrospective estimate of ionospheric
conditions and model the rx antenna, detector and headphones.
Since the tx antenna was a monopole one would predict that the odd harmonics
would be strongest:
ie approx 800, 2400, 4000, 5600, 7200, 8800..........
We know that the wind pointed the antenna East, hence rx antenna
directional gain would increase with frequency ( while the losses in the
detector would possibly increase with frequency).
One could model the vertical half bow tie TX antenna for the harmonics.
I am not very familiar with the transatlantic path, but 5.6 mHz harmonics
and up look good to me.
There was no independent witness for the reception so the possiblity of
deliberate fraud or honestly mistaking QRN for the "S' cannot be ruled out.
The Poldhu transmitter was also monitored by a ship and independent
witnesses heard the presumed fundamental at night up to 1500 miles out
which is not unexpected .Using computer modelling one could use this info to
get another estimate of the rx system sensitivity also. I believe the ship
antenna was a wire between the masts with a downlead worked against the
steel hull, would have been mighty on 800 or 2400 kHz.
Would love to hear the good Dr Bold's and others views on this.
73
end
Barry Kirkwood PhD ZL1DD
Signal Hill Homestay
66 Cory Road
Palm Beach
Waiheke Island 1240
NEW ZEALAND
www.waiheke.co.nz/signal.htm
----- Original Message -----
From: Gary Johanson <wd4nka@juno.com>
To: <david@computan.on.ca>
Cc: <glowbugs@piobaire.mines.uidaho.edu>
Sent: Thursday, 14 June, 2001 3:19 AM
Subject: Re: GB> update / marconi speculation.
> On Tue, 12 Jun 2001 23:50:30 -0400 David Wilson <david@computan.on.ca>
> writes:
>
> > It has a 1/2 KW 12,000 volt supply, and I feel I should be able to
> > get
> > about 100 watts out of her. I will inform the group of any testing
> > so
> > they can give me a report.
> > It has a rotary gap with 8 contacts in it turning at 1800 rpm so
> > it
> > will produce a 240 hertz note.
> >
> > cheers David ve3bbn
> >
>
> Hi, David:
>
> Rotary spark . . . hmmm . . . thought that was
> universally banned, but are they allowing
> exceptions in leu of the 100th anniversary ?
> ( personally, i hope so! I have always wanted
> to hear a genuine spark signal over the Ether
> with my own ears!! )
>
> Concerning that letter "S" transmission from
> Pohldu to [ was it ] Newfoundland (?) ---------->
>
> I have an interesting article from HRH speculating
> on the probablility of a signal, received in the after-
> noon on such a low frequency using propagation
> that does not normally occur during that time. (Even
> though it was winter, a good time for VLF)
>
> Either : 1) marconi was extremely lucky to have
> stumbled into just the right unusual circumstance
> to pick up a VLF signal in daylight hours using a
> receiver equivalent to a crystal set in sensitivity,
> ( which isn't impossible, but with a passive detector,
> unlikely ) or
>
> 2) He was actually listening to a shortwave signal
> and didn't know it. Apparently the original receiving
> site had to be shut down, and the receive apparatus
> was changed to a stand-by receiver at the new location.
>
> This other receiver was untuned. When the signal
> was received ( remember that the transmitting signal
> was a very powerful harmonic generator . . .something
> they didn't worry about in 1901 ) it was identified by
> the controled rythym of the three dits against the
> dinn of static crashes and general QRN. An easy letter
> to hear. A very real possibility exists that what marconi
> actually heard was a high frequency harmonic taking
> advantage of daytime propagation, which would
> present the detector with a fairly strong signal. Or,
> since the receiver was untuned, SEVERAL simultaneous
> harmonics !! ( there is some speculation concerning
> the kite-lifted antennae dynamics being resonant somewhere
> in the HF spectrum, which would tend to enhance reception
> of such a harmonic )
>
> So that trans-atlantic transmission may have also
> been the first SW trans-atlantic, after all.
>
> I am very careful to say that the author is purely speculating,
> necessary data was not taken, and none of us were there.
> Therefore, we'll never really know for sure. But it is an
> interesting speculation, none the less.
>
> ( I would like to reproduce the article, but copyright
> questions make this a dubious move. HRH has been
> gone now for twenty years, but still, you never know. As
> an alternative, i may reconstitute the bibliography and
> post the basic outline of the article for anyone to
> research for themselves to my site. If there is sufficient
> interest. )
>
>
>
> vy 73
> gary // wd4nka
> " . . . who forgets the past forfeits the future . . ."
>
> ________________________________________________________________
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