. QST . rground, a grounding 36 QST for stake should be located at the point where thecable enters the ground. The grounding stake,to be effective in soils of average conductivity,should be not less than 10 feet long, and ifpossible, plated with a metal which will notcorrode in the local soil. When open-wire feeders are used, a lightningarrester is required. The type of lightningarresters provided for residential broadcast andtelevision antennas may be suitable for very twelve years these gaps were in use there wasnever an occasion when a Ughtning hit camecloser to our house than a half block
. QST . rground, a grounding 36 QST for stake should be located at the point where thecable enters the ground. The grounding stake,to be effective in soils of average conductivity,should be not less than 10 feet long, and ifpossible, plated with a metal which will notcorrode in the local soil. When open-wire feeders are used, a lightningarrester is required. The type of lightningarresters provided for residential broadcast andtelevision antennas may be suitable for very twelve years these gaps were in use there wasnever an occasion when a Ughtning hit camecloser to our house than a half block when aneighbors house was struck. This could havebeen a happenstance but it is the fact, neverthe-less. In the Pennsylvania Dutch country aroundLancaster and York, most bams nowadays areprotected from lightning by a length of oldtrolley wire mounted on poles extending about10 feet above the roof. Both ends of the wire Fig. 2 — Sketch of coax-fed groundedZepp antenna. Adjustment is discussed inthe low-power installations but where higher poweris used, they are inadequate, since the radio-frequency voltage on the transmission line isusually enough to cause them to operate; ,flaah over. During the early Thirties, advice was obtainedfrom the Naval Research Laboratory at Washing-ton, D. C, on a suitable grounding arrangementfor lightning protection for a 1-kw. installation. Itwas their suggestion that a spark gap be providedbetween each of the two open-wire feeders and acenter contact, grounded with No. 4 or largerwire. It was recommended that 3^ X J/2-iDchflat brass rod shaped as shown in Fig. 1 be usedfor the gaps. Each of the gaps should be setsufficiently far apart so as to prevent flash-overduring normal operation of the transmitter. Itwas found that because of the standing waves onthe open-wire line a gap of approximately Keinch was necessary. This device worked very well during thunder-storms as it would start sparking intermittentlywhen a storm was approaching.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
