Topband: Short radials?

[Tom W8JI]

> It's important to note that this data is for AM broadcast towers, which in 
> the time frame when this work was done, were mostly a quarter wave tall to 
> 5/8 wave tall.  >

We should look at the data and not assume. The original paper is called 
"Ground Systems as a factor in Antenna System Efficiency" and based on a 
study for RCA corporation. It includes measurements of screened and 
unscreened systems, and concluded screens offer no additional advantage.

I'm pretty sure I have the original papers around here in a box someplace. 
The B L and E data is for various heights from very short heights up to 90 
degrees tall, with a variety of ground systems.

Very few AM BC towers are 5/8th wave. Many are shorter than 1/4 wave, and 
most are actually someplace around 1/4 wave tall.

Richard suggested one of the best sources for conventional radial system 
information on radiators less than 90 degrees tall. The graphs he posted are 
for radiators from a few degrees to 90 degrees tall.

On 9/27/2012 10:14 AM, Richard Fry wrote:
>> The measured data linked below shows how the number of buried radials 
>> affects the performance of monopoles of various height to 90 degrees, for 
>> an applied power of 1 kW.  Earth conductivity at the test site was about 
>> 4 mS/m.
>>
>> http://i62.photobucket.com/albums/h85/rfry-100/BLandERadials.gif
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