Posted by noel shelley on 20/06/2023 10:11:57:
Thanks for this thread Julian ! Having always had an interest in radio and the question of what was received and how, was 1912 a good year for skip conditions ? …
This graph is from the Wikipedia article on Sunspots, and attributed to NASA.
It shows that the sunspot cycle was at a minimum in 1912. Radiation from the sun varies on a 22 year cycle, not heat, but wavelengths that ionise the upper atmosphere, causing the Northern Lights and many invisible electronic phenomenon that affect radio signals all the time. Solar Storms occasionally disrupt power distribution systems on a continental scale.
What ionisation does depends on the layers height and the frequency of the signal. The layer can act as a filter or a mirror. Below a certain frequency, ionised layers tend to absorb radio energy, which is why the range of low frequency signals increases at night and drops during the day. In daylight, the layer is reenergised by the sun and gets thicker. The mirror is closer to the ground, reducing skip distance, and much of the signal is absorbed, not reflected. At night, the layer thins out, absorbing less of the signal, and the effective height of the mirror rises. More energy is reflected, and it's reflected from higher up, resulting in greater range.
As frequency rises, the ionises layer becomes more reflective, allowing short wave signals to bounce repeatedly, potentially circling the planet. But the mirror is easily penetrated by very short waves, which tend to be limited to just over the horizon range, and bounce off almost everything.
The above is a simplification: there are actually several layers, not always present, at different heights. As a result there are plenty of opportunities for anomalous propagation, where signals suddenly drop out or travel unexpected long distances.
Like the weather, propagation is fairly predictable. Depending on the date and time of day it's possible to exploit 'conditions' by selecting frequencies and antenna to suit the path and distance. Far from perfect service, for example the US Navy failed to warn Pearl Harbour that Japan was about to declare war because 'conditions' had temporarily disabled their direct radio link. Seems no-one though of trying the US Army circuit, so the message was sent as a civilian telegram, taking too long because it went by a mix of cable and shorter wireless links. The message was delivered by a man on a push-bike during the attack.
What effect might the sunspot low in 1912 have had on Artie? It will have caused long wave signals to travel further than normal, especially 300 metre wave signals. On the other hand low sunspots make transmission of short wave harmonics less likely.
It's hard to tell because wireless equipment in 1912 wasn't tuned. Later equipment is much sharper, essentially only sending and receiving on one narrow frequency. Artie's transmitter is only tuned very broadly by the aerial, which would respond well to fundamental and multiples, but also to almost everything else. His receiver is only slightly better. I believe the Titanic's antenna type tends to suppress even harmonics, but not odd. So a 300 metre fundamental might have a strong 75 metres component, that skipped, and was detected by Artie's simple system. The layer hypothesis was suggested in 1902, but there wasn't enough evidence to confirm the theory until 1923.
Early copies of Model Engineer magazine are full of Wireless projects. My 1919 example is entitled 'The Model Engineer and Electrician'. Lots of brass. Quite a lot of Artie's equipment is made with Model Engineering type metal work, greatly facilitated by a lathe which could also be used to wind those giant induction coils. I'm fairly sure his morse key is home-made, and probably many other small parts. I'd like to know where the metalwork was done. Possibly in the mill, more likely in one of the neighbouring collieries or railway workshops, where lathes were essential. Old maps reveal this part of Wales wasn't an agricultural backwater: young Artie probably had access to a wide range of technical skills and facilities.
Dave