In a message dated 9/16/99 7:13:33 GMT Daylight Time, [email protected]
writes:
<< To All,
As a answer to a question by Mike, G3XDV, I have sent the following e-mail
to the reflector:
>Mike, G3XDV wrote:
>
>
>> 1. No top load
>> Efficiency: 10.8%
>>
Hello Dick / group.
I recently installed a small broadcast transmitter on 1350kHz which was
licenced for a maximum antenna height of 10m.
After some time we managed to get a 10m glassfibre mast errected with a small
top capacity hat, inductive loading at the centre (Litz), together with an
element of distributed loading in the top section between the loading coil
and the top hat.
When examined by the authorities the efficiency was around 7%.
A rough calculation would suggest that the Rrad of a 10m vertical is no
greater than 0.1R, on 136k. The computers perfect ground assumption could be
affecting the ability to compare the effects of different arrangements for
top loading. Is it EZNEC which has poor / Avg / good / perfect / ground
models?
73
David. G0MRF
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