After W8JI comments and thinking about your station/antenna description and how
close things are to the house, I'd suggest you might want to update (you have
done them in the past, right?) the RF safety calculations to be sure what you
plan makes sense:
http://www.arrl.org/tis/info/rfexpose.html
-- Tom
At 11:44 AM 8/15/2001 -0400, Tom Rauch wrote:
>> Any thoughts and or practical experience would be appreciated! Many
>> thanks for your help.
>>
>> 73
>>
>> Bob KQ2M
>>
>
>Hi Bob,
>
>Elevated radials radiate like crazy in close to the radial, and couple
>to everything around the radial. There is nothing you can do about
>that radiation, it always happens.
>
>Remember what causes radiation, and what prevents it. In close to
>the wires, you will have very strong magnetic and electric induction
>fields. You will also have radiation that can only be cancelled by an
>opposing field that is out-of-phase and EQUAL to the fields causing
>problems. If you have four radials, you have 1/4th the current in
>each radial that you have in the vertical (less whatever follows the
>outside of the feedline shield away from the antenna making the
>coax radiate).
>
>If you run 1500 watts, you can consider that each radial is an
>antenna tied to a ~200 watt transmitter. The radiation from the
>radials caused by direct excitation of the radial by the transmitter,
>even in the best case, only cancels in the far field many
>wavelengths from the radial.
>
>It is difficult or impossible to predict the effects when you put a
>bunch of radiating wires together in a small area, but it likely won't
>be very much of an advantage!
>
>You not only suffer a loss of efficiency by having a small ground
>system, it aggravates RFI and coupling problems to other nearby
>conductors that are not part of the antenna system you are using.
>73, Tom W8JI
>W8JI@contesting.com
>
=====
e-mail: k1ki@arrl.org ARRL New England Division Director http://www.arrl.org/
Tom Frenaye, K1KI, P O Box J, West Suffield CT 06093 Phone: 860-668-5444
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