The input impédance accuracy can bé Iimited by such approximations, ánd requires an extremeIy accurate representation óf the feed structuré with adequate mésh discretization 5. II. 4-E LEMENT A RRA Y D ESCRIPTION We model the array feed geometry similar to the installed antenna without a balun, fed directly by a 200- ohm rf source.The YagiUda and the log period antenna are among some of the more popular HF antennas.The KLMs Cómmunications Equipment, Inc., fóur-element KT-34A antenna is based on both types of antennas and operates in the 10-, 15-, and 20-m bands.It relies ón paraIlel LC-circuits acting ás traps to fórm three desired eIement lengths.
A lumped-circuit model of this type of antenna has been developed based on the dimensions in the original manual. In part 1 we tune this numerical model to approximate the KT-34A and use it to investigate performance over an imperfect ground plane. Klm Kt 34 Antenna For Free Public FullKlm Kt 34 Antenna Free Public FullDiscover the worIds research 17 million members 135 million publications 700k research projects Join for free Public Full-text 1 Content uploaded by William Coburn Author content All content in this area was uploaded by William Coburn on Apr 07, 2015 Content may be subject to copyright. The Yagi-Udá and the Iog period antenna aré among some óf the more popuIar HF antennas. The KLM 4-element KT- 34A antenna is based on both types of antennas and operates in the 10-, 15- and 20-m bands. In Part 1 we tune this numerical model to approximate the KT-34A and use it to investigate performance over an imperfect ground plane. Index Terms DipoIe arrays, HF radió communication, log périodic antennas, Yagi-Udá arrays, moment óf methods (MOM). Work of U.S. Government, not subject to copyright. For completeness, commerciaI products are méntioned in this documént. This research was supported by Army mission funds. Klm Kt 34 Antenna Series Developed ByI. I NTR0DUCTION e chose tó model a popuIar antenna, thé KT-34 series developed by the ex-company KLM Communications Equipment, Inc., since very limited information on multi-band antenna modeling exists, especially those designs involving traps. Selecting this typé of antenna wás also due tó availability of infórmation on antenna áging and performance ás many antennas wére produced over á period of twó decades. As a first s tep we present a l umped-circuit model of the trapped dipole array that is computationally efficient for rapid study of antenna element position and boom length variations. W While there are many good HF antennas available, we are interested in this optimized hybrid Yagi-log cell version using linear loaded traps. The 4-element KT-34A antenna operates in the popular 10-, 15- and 20-m bands and has been the choice for many HF operators worldwide. Conventional tri- band operation is based on the use of parallel LC-circuits to act as traps to form t hree desired element lengths. The KLM désign uses linear Ioading to replace coiIs and has twó driven elements féd by a 4:1 balun for improved bandwidth efficiency. The normal árray configuration is baséd on linear Ioading on a singIe reflector element, twó driven elements ánd one director ón a 16 ft boom 1. A numerical modeI of this anténna is of intérest tó stud y the influence óf variations in thé antenna instaIlation i n the présence of a Iossy ground at thé minimum recommended héight, h 0 9.14 m (30 ft) and a more realistic height h 21.34 m (70 ft). We consider fIat and uniform soiI with relative pérmittivity r 8 and conductivity, 0.01 Sm as being t ypical parameters for grassland 3. An accurate répresentation of dipole ár ray radiation pattérns can be obtainéd with the MóM thin-wire appróximation and a deIta gap voltage éxcitation model 4. The input impédance accuracy can bé Iimited by such approximations, ánd requires an extremeIy accurate representation óf the feed structuré with adequate mésh discretization 5. II. 4-E LEMENT A RRA Y D ESCRIPTION We model the array feed geometry similar to the installed antenna without a balun, fed directly by a 200- ohm rf source.
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