Satgen 498 Magnetism Pt5 by GM4IHJ (BID SGEN498) 1998-10-09 Sometimes, both Mother Nature, and our fellow men, conspire, to create problems for us. A typical example occurs when anyone tries to gauge the magnetic features of a particular area or place. Many years ago IHJ moved to a new residence. Up went a mini mast and on it perched a 2m yagi ready for attempts to operate through Oscar 6, a mode A 2m up 10m down analog satellite. The antenna was aligned accurately on north using the pole star. Then it was trained west , that being the preferred azimuth for trans atlantic QSOs . But was the rotator accurate ?. Trying to check this using a magnetic compass proved to be totally frustrating . Away from the antenna , far enough to get a good line of sight along it , the compass suggested it was facing south not west . In the end a plastic geometry kit protractor was acquired , set up to north , then a string was drawn away from it at exactly 90 degrees to north along a westerly line , which was then found to line up with where the rotator said west was. Why was the first class army marching compass , so wrong. Carrying it around the site eventually revealed that the neighbours wrought iron fence was highly magnetic , such that anywhere within 30 ft of it produced a compass alignment dictated by the fence , not the earth. This giant magnet had been produced when the bars of the fence had been forged from molten iron. At a temperature around 600 C, the magnetic molecules in the iron are "loose" ( not confined in a tight crystalline structure). So they all line up beautifully in the earth's magnetic field present in the iron foundry. Then as the metal cools and solidifies they hold this alignment and thereby retain the maximum possible permanent magnetic field available with that material. So please be warned . Any magnetic material which has been allowed to cool through it so called Curie point , can give you problems. Which is where Mother Nature comes in , in respect of the magnetic nature of the hills around the IHJ QTH. Within 3 miles there are 7 extinct volcanic stumps. 500ft high piles of basaltic rock. All that is left of volcanoes which last erupted 250 million years ago. Basaltic lava contains a large proportion of the mineral magnetite, which as its name suggests can be magnetised. When this lava cooled through its Curie point Scotland was near the equator at a very different alignment to the then magnetic poles, from the one we now experience. So the magnetite is magnetised in a direction quite different from the present direction of the earths magnetic field. So wandering around locally with a magnetic compass as your only navigation aid , is not recommended. Indeed one local racing pigeon fancier blames these volcanic stumps for the poor performance of his birds . Many of whom simply never make it back home - whilst those of a reportedly thick type who knows nothing about pigeons but lives in an area free from ancient volcanic stumps, wins all the races.