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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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4th Apr 2021, 9:32 pm | #21 |
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Re: Marconi Wireless Station Clifden
Correction 500Hz not 8kHz.
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5th Apr 2021, 10:48 am | #22 |
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Re: Marconi Wireless Station Clifden
In 2017 on a grey day, there are lots of grey days on the west coast of Ireland, Anne & I went and had a look.
There is little left, a few foundations and scars on the landscape. The authorities there have made the best of what remains. There is a car park and a walkway with duckboards and a number of display posters with explanations and photographs. It's a very bleak bog! |
5th Apr 2021, 1:59 pm | #23 |
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Re: Marconi Wireless Station Clifden
I have never been there but can well imagine the bleakness. Emeritus has already mentioned the virtues of the location. The initial trans-Atlantic station was at Poldhu in Cornwall and there Marconi was experimenting with aerials such as inverted cones of multiple wires held up by four towers set as corners of a square. Then this scheme was greatly extended in all directions to form a giant umbrella of wires. Further tests showed that horizontal wires gave good reception when the open end was pointed away from the direction of the transmitter and this evolved into the inverted L where the horizontal part was significantly longer that the vertical. At this stage they realised that the Poldhu site was too small and explored the west coast of Ireland. The Clifden site was closer to Glace Bay across the Atlantic and as Emeritus has said it offered a ready supply of peat for the power generating plant in addition to offering a nice damp earthing field for the aerial system. In fact the earthing was augmented by running wires in the ground under the horizontals of the aerial.
Three 5kV steam turbine DC generators (see photo below) were connected in series and could be used directly or to charge the 6000 2 volt 40AH cells of the battery. On battery alone the station was run at between 11kV and 12kV or with generator and battery used together at 15kV. The inverted L gave very significant improvement over the previous Poldhu arrangements in terms of reception and transmission by virtue of its directional properties. Although rather massive the air spaced condenser system at Clifden was also a big improvment over the glass dielectric condensors at Poldhu. The 30' x 12' plates at Clifden were spaced 12" apart and no lasting harm came to the air spacing in the event of flash overs. See photo below. Peter |
5th Apr 2021, 4:00 pm | #24 |
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Re: Marconi Wireless Station Clifden
12kV at 40 Ampere hours, is just a whisker short of half a megawatt-hour!
Very scary. David
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5th Apr 2021, 5:58 pm | #25 |
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Re: Marconi Wireless Station Clifden
Yes, Almost everywhere you look it was scary. Looking at the right hand side of the diagram in Fig 24 the secondary winding to the aerial is on the left side of the photo below and the primary is just two turns of 12" diameter "wire"!
The operator's key on the output of the 12kV DC generator also looks a little scary although I think there might have been some element of remote control there in practice. Peter |
5th Apr 2021, 6:21 pm | #26 |
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Re: Marconi Wireless Station Clifden
Or, if you like that sort of thing, being hit by a ten-tonne truck, 480 times! (Joules = 0.5 * kg * (m/s)**2; v = 60 mph = 96560.64 m. in 3600 sec. = 26.8224 m/s.; so KE = 0.5 * 10000 * 26.8224 * 26.8224 = 3.597e+6 J.)
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5th Apr 2021, 7:11 pm | #27 |
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Re: Marconi Wireless Station Clifden
Ground radials are the usual means of earthing VLF / LF antennas. The wet peaty bog would've been considered a bonus. That the station was on the coast would've helped too.
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6th Apr 2021, 7:28 pm | #28 |
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Re: Marconi Wireless Station Clifden
Re the photo of the condenser in #23, the same picture appears in a booklet publishd by Marconi a couple of decades ago. Its caption says that it shows the condenser under construction.
Last edited by emeritus; 6th Apr 2021 at 7:30 pm. Reason: typos |
6th Apr 2021, 8:10 pm | #29 |
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Re: Marconi Wireless Station Clifden
Yes, indeed. I think the Condenser House was fairly well filled with plates. Certainly you can get that impression if you calculate the volume of 1800 plates 30' high by 12' wide and spaced 12" apart then compare with the shed 360' x 75'.
Peter |
6th Apr 2021, 8:43 pm | #30 |
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Re: Marconi Wireless Station Clifden
I have removed several messages at Peter request can he confirm that is correct
Cheers Mike T
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6th Apr 2021, 11:03 pm | #31 |
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Re: Marconi Wireless Station Clifden
Yes, thanks Mike. You removed the posts I asked to be removed.
Peter |
6th Apr 2021, 11:39 pm | #32 |
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Re: Marconi Wireless Station Clifden
Thinking about that condenser house, it would have been extra large even considering the voltage, for added clearance to allow for the humid conditions.
David
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7th Apr 2021, 8:41 am | #33 |
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Re: Marconi Wireless Station Clifden
Ventilation clearly did present an issue. The early photos show just two chimneys at the central area but later the two has become twelve.
Peter |