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Ermi wrote: *I don’t know if Brown’s 22 degree antenna was top loaded or not. I presume that it was top loaded, since, with a radiation resistance of 1.474 ohms, the ground resistance would be .182 ohms, which is too low to be practical. With a radiation resistance of 5.9 ohms, the ground resistance would be .729 ohms, which is also low.*

None of the monopoles in the BL&E experiments was top loaded. As for the r-f ground resistance, the analysis in their IRE paper states, “We see that the power lost in a ground system consisting of 113 wires, each 0.4 wave length long is insignificant.”

This result also is shown by their Figure 18 plot of power lost in 113 each, 0.4-lambda radials at all monopole heights measured ranging from 22 to 88 degrees. Of interest is that Figure 18 shows 745 watts as lost in the ground system of a 22-degree monopole using only 15 radials each 0.4-lambda long, for 1 kW of applied power. All of this is shown for a ground conductivity of 2 mS/m.

*Some additional metallic ground plane is necessary to ensure that the needed efficiency is obtained.*

None is shown needed or used in the BL&E experiments to produce the results they measured for the 22-degree monopole with 113 each radials, each 0.4 lamda long.

At this point I’ll include two links.

This one http://i62.photobucket.com/albums/h85/rfry-100/BLEMonopoleComparison.gif shows NEC-2 calculations and a comparison of the elevation patterns and gains for a lossless 22-degree monopole without top loading, and a 1/4-wave monopole — both over perfect ground.

This one http://i62.photobucket.com/albums/h85/rfry-100/BLESimulation.gif uses the 0.38 dB difference in h-plane gain for the 22-degree, perfect monopole from the NEC comparison, along with values taken or implied by the BL&E paper for this configuration. The frequency, monopole height and monopole OD are those used by BL&E.

This simulation shows that the BL&E-measured field equal to 283 mV/m at 1 km for 1 kW of applied power is achieved by this configuration as long as the matching and r-f ground loss total is not more than 0.149 ohms. BL&E state that the reactance of the monopole was determined by varying the value of a condenser (capacitor).

*As for Brown’s results, the ground resistance clearly has to be too low for them to be completely correct.*

The r-f ground loss for the BL&E system of 113-radials each 0.412-lambda long certainly is much lower than most licensed AM stations. But then very few of them use radials longer than 1/4-lambda. Dr Trainotti suggests that about 120 buried radials each 1/2-lambda long used with a monopole virtually is a perfect r-f ground. BL&E’s measurements show that they got very close to that.

*He* [Brown] *probably reported exactly what he measured. As has been already pointed out, it is not easy to measure field strength with high accuracy.*

My money is on Dr Brown and his team, who still are very highly regarded as pioneers in broadcast engineering. Their field measurements were within 1.5% of the theoretical value for that radiated power for a perfect 1/4-wave monopole over a perfect ground. Accurately measuring the change in that field from a 22-degree monopole, other things equal, is not technically difficult. The BL&E findings in these experiments became the basis for the minimum performance required by the FCC for licensed AM stations, to this very day.

For those who may be interested, paper 4 at this link http://rfry.org/Software%20&%20Misc%20Papers.htm is a PDF of the IRE publication of BL&E’s experiments, and their results. It makes for very good reading and study. I hope anybody finding anything in conflict with what I have posted based on the BL&E paper will let me know.

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