[BC] Base Insulator Elevation

[Mike McCarthy]

  If the station was in the 500-600 range, that 25 ft. could be only 5 
degrees.  Not enough to cause radiation issues like you state.  OTOH, at 
1600, that's 20 deg. and plenty enough to cause issues.

In our other situation which we needed to elevate the base (10ft.), we 
mounded the soil around the tower base level to a distance of 25 ft. in 
all directions so as to eliminate that issue and include a screen around 
the tower like all the other towers of the array.  It tuned up as expected.

Granted, that same process on a 25 ft. pier might be a bit more 
work....and subject to a greater amount of settling.

MM

On 11/13/2010 1:56 PM, Richard Fry wrote:
>> Years ago, there was not much choice - one six tower array I built
>> followed the consultant's instruction and had 25 foot piers at one end,
>> while the other end was right at ground level.
> _________________
>
> But if the monopoles on 25 foot piers were series-driven across a base
> insulator, and used copper strap running down the pier to connect to a
> buried radial r-f ground system, then the radiation from that copper strap
> would change the radiation patterns of those monopoles compared to the ones
> installed at ground level.
>
> A NEC model of the system could predict what net effect that would have on
> the az/el patterns from the array.
>
> RF