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Antenna Loading Capacitors

March 4th Fact-of-the-Day

It is well known that a loading coil can be connected in series with a short antenna to make it resonate at a lower frequency. It may be slightly less well known that a loading capacitor can be connected in series with a long antenna to make it resonate at a higher frequency. However, there is an important difference beyond the opposite frequency effects. One or more series loading coils have no significant effect on the radiation of pattern of a short antenna, regardless of their positions, but that is not true of one or more loading capacitors placed in series with a long antenna. Series loading capacitors of the correct size can be distributed along the length of a long antenna such that maximum radiation will be broadside even if the antenna is several wavelengths long and such that there will be appreciable gain in the broadside direction compared to a halfwave dipole. ©2005 Martek International All rights reserved.


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