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The images on this page were kindly supplied by Chris Rees, and show the Alderney NDB in the Channel Isles, and also the old dilapidated former VOR system, which can be seen here through the gateposts of the WW2 SS concentration camp 'Lager Sylt'. Chris also says that the white smudge just above the right-hand pillar is the French nuclear reprocessing plant on the top of the Cap de la Hague, 8 miles east across the Alderney Race, and that he's happy that the prevailing winds are from the south west!:-)
Chris also pointed out that the NDB has an interesting feed arrangement, which he hasn't yet worked out, and I noticed that this is identical to the one on the new Sligo NDB, so this seems to be a popular feed method these days. Since the top part of the tower is usually 'live' with RF I would suspect that the two interwoven coils form some sort of 1:1 transformer/isolator, and the two balls a spark gap for lightening protection, but if anyone knows for sure, or can recognise who the manufacturer of these typs of antennas are, please do let us know.
NOTE# Our thanks to Telecommunication Engineer Gray Frierson Haertig for the following information, which explains a lot about something that we have seen on a number of the NDBs, and often wondered about:
"The interlaced coils that you see are called an Austin Ring Transformer, after the original manufacturer. Austin is still in business, though I don't know if the transformer pictured is manufactured by them. It is used to couple the AC power for the aviation obstruction lighting across the base insulator of the tower while having very little affect on the base impedance of the tower at the RF frequency. It is, indeed, a 1:1 transformer. The spark gap (colloquially known as Johnny balls in US parlance) protects the transformer from lightning. There is an independent spark gap to the insulator rain shield on the leg nearest the camera. The actual RF feed is coming out of the piece of flexible tubing connecting the tower to the piece of duct emerging from the base slab. Presumably the antenna tuning unit is located in the building adjacent".
Thanks for that Gray, very much appreciated!
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