Journal of the Royal Naval Scientific Service. Volume 29, Number 6 ...

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Wrap-Round Antenna: Wyatt 255 FIG. 5. Vertical radiation patterns. FIG. 6. Vertical radiation patterns
256 J.R.N.S.S., Vol. 29, No. 6 FIG. 7. Vertical radiation patterns. was co-linear to the transformer with the four feeds coming off radially at right-angles. Although this is a reasonably simple device to match, the cable take-off bights to the elements would force the transformer away from the mast causing location difficulties. The final design of splitter was placed at right-angles to the transformer so that the feeds came off in the same plane as the transformer. This presented matching difficulties because of the violent change in the symmetry of the system. Without matching sleeves, the transformer plus splitter V.S.W.R. was better than 1-2 and after matching, better than 1-06. The matching sleeves were made from P.T.F.E. to cover breakdown requirements. Linearity Fig. 8 shows the arrangement of the linearity test site. Two transmitters Type 692/693 delivering frequencies U and f 2 at 20 watts each, are fed to a common junction via tripletuned cavities tuned to these frequencies. From the junction, fi + f 2 are then fed via 180 feet of buried \ inch air-spaced, flexible, solid-outer cable to the object under test. Any non-lineariur in the object will create the third order inter- modulation (i.p.) 2fj ± i 2 (this is the i.p. of the largest amplitude). The frequencies of the transmitters are therefore chosen so that fi f 2 and the i.p. frequency lie within the 225 - 400 MHz band. On reflection the i.p. will return to the common junction and will enter the third triple tuned cavity which has previously been tuned to the i.p. frequency. The receiver used had a sensitivity of 1 microvolt which is 150 dB down on 20 Watts at 50 ohms which adequately covers the antenna specification of 120 dB down on 20 Watts. Because the layout of the active and passive components necessitates the use of a number of connectors each of which could produce non-linearity, it is well to have a reference standard to check the system each time it is used. During the period of the linearity check on the wrap-round antenna, such a standard was available in the form of the all-copper version of the aluminium antenna Type AJE (see Introduction). This version is designated UK SAR 102 and has a linearity greater than 150 dB. Four wrap-around antennas were checked and each has an i.p. greater than 135 dB. This high order of linearity was achieved by careful detail design:
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Page 27 and 28: FIG. 1a. Distribution of R. fOO tio
Page 29 and 30: Reliability Assessment: Lukis 275 R
Page 31 and 32: P. and fi.E. Inchterj: McLanuclian
Page 33 and 34: (4) Process and General 8 Superviso
Page 35 and 36: P. & E.E. lnchterj: McLanachtm 281
Page 37 and 38: As regards assessment studies, the
Page 39 and 40: 285 Vickers Oceanics take over most
Page 41 and 42: 287 The Controller of the Navy. Adm
Page 43 and 44: Notes and News 289 First Sea Lord a
Page 45 and 46: 291 BOOK REVIEWS Theoretical Nuclea
Page 47 and 48: 293 INDEX TO VOLUME 29 1974 Persona
Page 49 and 50: Index 295 Lakey, J. R. A. The Third
Page 51 and 52: [dstl] Information Centre Knowledge

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