Special charts are required for Consol fixes and are available from the 

 hydrographic establishments of England, France, Germany, Denmark, and Spain. 

 They are in mercator projection and contain the great circle bearings from each 

 station. The lines are numbered and dot-dash characteristics are noted. 



3. ACCURACY 



The accuracy of Consol and Consolan fixes depends upon the distance 

 of the receiver from the transmitter and upon its position in the field. It is gen- 

 erally felt that adequate fixes can be generated within a 70° sector either side of 

 the normal to the line of transmitting antennas. 



Receiver signal-to-noise (S/N) ratio will materially affect the useful 

 over-all system range. Atmospheric static noise is proportional to the receiver 

 (B^) 2, Because the Consol signal is single frequency cw, a narrow-band filter 

 can be used to improve the S/N ratio. 



The polar diagrams plotted in Figure IV-2 tend to indicate reception to 

 an infinite range. Application of a correction for reception at infinite range shows 

 that the principal effect is a reduction in discrimination due to a poorer S/N ratio. 

 The noise between dots and dashes builds up, thus making them more difficult to 

 count . 



Figure IV-3 indicates some typical signal strength curves for a 1-kw 

 transmitter, y^' It should be noted that the sky wave is stronger than the ground 

 wave during evening hours at all but short ranges of less than 200 miles. Lower 

 frequencies are used in the U.S. version, and the useful range is thereby in- 

 creased. 



An area within which the reduction of the discrimination is 30% or more 

 is bounded by a curve of which the radius vector is proportional to the sin of the 

 azimuth. The maximum vector is at right angles to the line of the masts and is 

 approximately equal to 12 times the mast spacing. Considering an antenna spacing 

 of 3 ^ and utilizing a frequency of 300 kw, we find that within a circle of 15 - 25 

 miles the bearing taken with Consol will be inaccurate. 



By utilizing antenna spacing of about 3 ^, the narrowest sector generated 

 is 10°, giving a theoretical bearing accuracy of 10/60 or 1/6° (using German 

 cycles). Due to the form of the polar diagram, accurate vectors can be obtained 

 over an arc of about 70° on each side of the bisector of the line of masts. Because 

 the width of the sectors increases as the radius vector approaches the line of the 

 masts, bearing accuracy deteriorates to about 1/3° at the extreme of the arc 

 coverage. 



39 



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