Marconi’s Transatlantic Wireless Achievement by John Heys G3BDQ


I am a natural sceptic and seldom accept the first accounts of odd happenings seen on the TV or read in my newspaper. There is often a considerable time between the first reports and an eventual truthful story relating to the happening, the rapid and normally accurate reporting of events may at times be completely wrong and then there are red faces all round. The transmission of wireless signals across 2,000 miles of sea achieved by the young (27 year old) Marconi and his assistants gripped the public’s imagination and it was instantly accepted as a true fact with few, if any media pundits questioning its authenticity. The general public understood little of the growing science of wireless communication and were in no position to question the presented facts. It has only been in later years that questions were and are being asked as to whether Marconi had made the gigantic leap of just a wireless range of 80 miles to the 2,000 miles between Cornwall and Newfoundland on December 12th 1901.

His reception of a few Morse dots (3 to make the letter S) on Signal Hill close to St. John’s Harbour Newfoundland was at close to midday there, some 2,200 miles from the transmitter at Poldhu in Cornwall. His previous best was the reliable wireless link between Dover and Wimereux. The French station was also being received in Chelmsford at the Marconi works some 80 miles away. Today it seems a rash adventure to then begin planning a really long distance hop to North America.

The reason was perhaps because already he was seeing his work copied and improved upon by experimenters in other countries. Marconi was desperate for finance and knew that success or failure with his transatlantic venture would result in business success or failure. He aimed towards a rapid Company growth and he had to be one big jump ahead of other new and growing wireless companies. His successes were soon rewarded. He was acclaimed internationally as ‘Mr. Wireless’; shared the Nobel Prize for Physics in 1909 and was showered with honours for his achievements. Poldhu Signal Hill was perhaps the most important factor leading to his later wealth and recognition.

In the early days of the 20th century Marconi believed that wireless waves followed the surface of the Earth whether it was over land or sea, and the distance the waves travelled depended upon the radiated power, the receiving potential of the aerial systems and the sensitivity of the receiving apparatus. At that time the concept of long distance communication enabled by the ionosphere was not known.

The Poldhu transmitter, then the most powerful in the world had a power input of about 15 kW and was set to operate on a wavelength of approximately 366 metres (somewhere between 500 and 850 kHz). The transmitter spark must have generated many harmonics so the actual power radiated on 366 metres was considerably less than 15 kilowatts perhaps no more than six or seven. Marconi was bedeviled by bad luck regarding his antennas. Originally at Poldhu he had a large circle of twenty 200 ft masts (wooden ) each in three joined sections. These supported an inverted cone of 20 wires joined at the bottom and fed into the transmitter hut. Each mast had outside guy wires (broken with insulators) and a circle of rope joining the top of each mast. Unfortunately a severe Cornish gale and a weakness in the guying resulted in the complete destruction of the aerial system on September 17th 1901. An emergency replacement aerial was created seven days later. This was just a pair of masts which were well guyed and supported a fan of many wires which descended and were joined where they fed through the transmitter building roof.

Marconi originally planned to have the receiving station at Cape Cod in the USA, and in the autumn of 1901 a circle of masts was arranged which matched the aerial system at Poldhu. This new array was also destroyed by a strong gale at Cape Cod. This prompted Marconi to move the location of his receiving station to Newfoundland. No permanent aerials were erected at this new site and instead it was planned to have an aerial held up by large kites. The actual aerial was a 500 ft long wire, which used a buried earth system made with large zinc plates. I feel he would have been better served if those metal plates had been in the sea below the cliff top where the receiver was to be located. This vital piece of equipment was an Italian Naval Coherer which seemed to act as a detector giving signals that could be heard in a telephone earpiece. The receiving apparatus could not be fine tuned to the transmitter wavelength and this reduced the aerials effectiveness. There was no kind of amplification used, just the natural gain of the 500 ft wire. The receiving station was housed in two rooms of a disused fever hospital which was attached to a military barracks.

The actual date and time that Marconi claimed the reception of the three dot signals from Poldhu was 12.30 pm Newfoundland time on December 12th 1901. It is recorded that Marconi passed the earphone to his assistant Kemp, asking if he too could make out the signals through some atmospheric noise. This noise, even without receive amplification would have been quite considerable on the wavelength of 366 metres. Kemp stated that he too could make out the dots.

There are several reasons why we must cast some doubts on the reception of the Poldhu transmitter. The time of day at the American end of the experiment together with the wavelength used suggest that there could not have been a radio path from Cornwall. It was just getting dusk at Poldhu but in full daylight in North America. Over the years and up to the present time there have been many powerful broadcast stations along the East coast of Canada and the USA, stations using considerably higher power than the inefficient Poldhu spark transmitters with broadcast stations over the medium wave broadcast band. They could not be received, even when using efficient receivers over here in Europe. Even on the higher frequency amateur band of 160 metres the propagation does not allow transatlantic communication at the time used in 1901.No radio operator would even consider trying to receive signals between Europe and North America during the hours of daylight.

As a scientific experiment Marconi’s tests had an inherent weakness. The Newfoundland listeners should not have known the exact nature of the Morse signal. There are several Morse letters of the alphabet which have three elements using dots or dashes. At each end of the experiment there should have been respected observers who could have, at the last minute decided upon the transmitted Morse letter or actually listened to the received signals at the Newfoundland end. The decision at Poldhu could have been delayed until almost the last minute.

There is no reason to suspect Marconi and Kemp of calumny, I am sure that they both honestly believed that they had picked out the three dots through the static crashes. This kind of self deception is common and does not point to the fabrication of events.

There remains a useful ‘cop out’ in favour of Marconi. The signals they heard could have been much higher frequency harmonics for there was not enough selectivity at both ends to suppress them. These high frequency harmonics could have been propagated via the ionosphere in broad daylight. Marconi’s venture was not without risk but its success ensured a very profitable future for him and the growing Marconi Company which was soon involved in all kinds of radio exploitation.

Even today, Marconi is revered as the ‘inventor of radio’ and there is even an annual amateur radio Marconi Day when many of the sites he used for his early work more than a century ago are used to house temporary amateur stations. One must admire Marconi’s chutzpah. He was fortunate in having the world accept that he had spanned the Atlantic with his wireless waves.

I must apologise for not presenting any illustrations to accompany this article, for despite the hundreds of books about the man and his work there remains a very tight copyright over the reproduction of photographs.

By John Heys G3BDQ – Vital Spark July 2012.

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