Topband: Anyone purchased the ARRL book on Short Antennas for160???

[Merv Schweigert]

I live on a former AM BC site,  and cannot see any way that you could 
put up
4 elevated radials and disconnect the ground system that was in place.
The ground system here is typical installation and it is bonded with 4 inch
copper strap to everything and anything in sight.   The tuning networks 
in the
antenna huts were built on aluminum panels that are grounded with 4 inch
strap to the radial field,  all gear in the transmitter building is 
grounded with
4 inch to the radial field ground.  So its virtually impossible to 
isolate the
gear etc from the ground system,  installing 4 elevated radials really 
showed
nothing at all unless they dug up the entire radial field and pulled 
them out.
My door and window frames,  steel roof and every water pipe are connected
to the radial system.
When running 50KW you dont enjoy RF burns.

My field here has 120 - 300 ft plus and 120 - 60 foot radials,  Im sure 
4 elevated
radials will do very well.

73 Merv K9FD/KH6

> Dave W0FLS wrote:
>> With the radials being 4.9 meters above ground, do the radials 
>> literally come up to the tower and then travel down the leg to 
>> connect to the ground side of the insulator or do they travel in 
>> close to the tower and angle downward?
>
>> From the text of that paper, it appears that the four horizontal 
>> radials are 
> attached to the monopole by insulated supports at 4.9-m elevation 
> points above the earth, and terminate there.  The coax center 
> conductor is bonded to the tower at that same elevation, and the coax 
> outer conductor attaches to the common point of the four horizontal 
> radials at that elevation.
>
> There is no need as far as system radiation efficiency for any of the 
> conductors of this antenna system to have a physical connection to the 
> earth.  Probably this system does have conductive paths provided by a 
> static drain choke to a "lightning ground" buried in the earth (maybe 
> a few ground rods), and an arc gap across the base insulator -- but 
> the paper did not include those details.  They would have almost no 
> affect on the radiation efficiency of this system, in any case.
>
>> Does a FS measurement taken at 1 kilometer fully reflect the true 
>> angle of radiation and overall performance of the antenna for 
>> purposes of distant signals?
>
> The relative field (E/Emax) of the vertical plane field pattern 
> radiated by __all__ monopoles of ~ 1/4-wave in height and less is very 
> close to the cosine of the elevation angle.  The cosine of zero 
> degrees is 1 (unity), which means that maximum field is radiated 
> toward the horizon.  The cosine of 30 degrees is 0.87, which means 
> that the field at that elevation angle is 87% of the field in the 
> horizontal plane.  Etc.
>
> Referencing back to Clarence Beverage's data, this means that the 
> field at 1 km radiated by that system toward a 30-deg elevation angle 
> is 0.87 x 302 mV/m = 263 mV/m (approx).
>
> The relative values of those fields at an infinite distance over a 
> real-earth ground plane no longer have the relationships they had at 1 
> km, but that does not alter the fact that those relationships existed 
> at that 1 km distance, in the first place.
>
> R. Fry
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