[BC] Ground system

[Milton Holladay]

This is covering old ground; check the archive
There are optimum radial lengths, just as with buried radials.

More than four radials will start to push the point of diminishing 
returns due to excessive coupling to earth, which already needs to be 
avoided by elevating the radials >=1/12th wavelength, IIRC..  Six will 
likely start to exceed it.

The extant authority is Wm. Culpepper in Charlotrte, who has gotten 
several stations licensed with elevated radials ( I participated in 
measurements on his test site in the early 90s.) .............
M

On 2/10/2012 16:57: VIRUS ALERT!, Craig Healy wrote:
>> The solution is an above-ground counterpoise made from Alclad or
>> similar materials. For AM nondirectional antennas, four 1/4
>> wavelength-long radials, insulated at their ends, and supported
>> by utility poles have been proved to make the required FCC
>> inverse-distance field intensity, and the far-field is nearly
>> circular.
> That is done on the 640 station in Philadelphia, from what I'm told.  One
> issue is significant voltage at the end and the fact that the radials are
> quite bandwidth-specific.
>
> Would it be better to use six elevated radials, but connect pairs at the
> ends so there are three sets of more broadband versions?  Picture the dipole
> antennas used for VHF and UHF that are essentially triangular.  An
> effectively wide radial may be better.
>
> Craig Healy
> Providence, RI
>
> Milton R. Holladay Jr. / miltron at att.net
> Columbia, S. C. / 803-331-8059
> RF Measurements / Planning&  Installation / Emergency Service&  Parts