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Remote Inductive Tuning

November 18th Fact-of-the-Day

Remote adjustment of antenna tuning and phasing networks often is accomplished by means of motorized variable capacitors. However, variable capacitors have become scarce and expensive. Some also have wiping contacts that are troublesome. Small tuning or phasing network adjustments can be made inductively instead by simply rotating a copper disk or doughnut-shaped copper ring inside a tuning inductor. RF losses from this method are very small even though the disk or ring constitutes a short-circuited secondary-winding so long the disk or ring has very low RF resistance. This is demonstrated by the fact that such a disk or ring does not warm significantly even when used with high power transmitters. ©2004 Martek International All rights reserved.

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