Output on the ol' blog is a bit slow these days. Well, there is plenty else to do, and radio sometimes has to take a back seat.
Added to that has been a survey I started, mostly out of personal curiosity, of the 1914-1939 Marconi VLF site at Cefn Du, near Caernarfon (then anglicised to 'Carnarvon').
Superficially, there is not much to see here these days. The transmitter and power buildings are still here and very identifiable forms reproduced at other contemporary Marconi stations, notably Stavanger. Otherwise, there are just the concrete stay anchors to see.
 |
| A 2017 Marconi Day outing with the local club gave us a chance to look at the lower anchor blocks. |
But, by walking slowly and carefully around, detail - a lot of detail - starts emerging. Consulting some books, internet archives of journals of the time and the Marconi archive itself, something much more like a complete picture has come together.
It's not been easy, and it's far from complete at the moment. The mountainside site is exposed and boggy in parts (wet sites were deliberately sought for Marconi stations - they believed this provided an "electrical connection to the sea"). In other parts, it's thigh-deep heather, making walking and finding things through it really very difficult indeed.
 |
| Footpads of a 400' (122m) high triangular mast for the 1924 antenna extension - and some 20m WSPR with SES callsign GB1MUU! |
Sadly, due to copyright constraints, I can't yet show you any images, other than what is already in the public domain.
So, for now, here is a screengrab of what has developed into a complex plot of features on a Goole Earth Pro background. When it's finished, I'll be releasing the .KMZ file, so that it's easier to see and understand, together with some simplified plots to show particular features.
The main features are:
(1) The first antenna, completed 1914, runs from the TX house at far left, the yellow circle and emergent yellow lines representing the (outer limit of) an earth screen system. This was buried around and beneath the antenna initially.
(2) The extension (later split to operate as a separate antenna) to the 1914 antenna, completed 1924, and running to the upper right. The 1924 extension, running at an angle of 130 degrees to the 1914 antenna, is a tacit admission by Marconi that the inverted-L antenna was not directional in the manner he had long claimed - see contemporary field strength plot, more like a 2-element beam, below:
(3) The dark purple lines are the wires between lattice masts that supported an extensive, matched meshed-wire counterpoise. The full arrangement was too dense to be represented fully. Pink lines are trackway routes.
(4) Blockhouses around the perimeter of the site, which were manned by the military under fear of sabotage.
 |
| The pyramidal peak of Yr Wyddfa ('Snowdon') at right provides a beautiful backdrop for the Marconi MUU site. Even substantial structures are now beginning to be buried under moss, grass and heather. |
Naturally, all content is strictly (C) MW1CFN, 2022.
