To: <towertalk@contesting.com>
>Date: Mon, 01 Jun 1998 12:32:36 -0700
>From: Fred Roberts <froberts@pe.net>
>
>Tom Rauch wrote -snip-
>
>> My grounded plummer's delight 5 element 20 meter beam was useless
>> during foul weather (it was at 160 feet, the highest antenna on the
>> stack), while lower antennas were pretty quiet. After I installed a
>> tall 2 meter vertical above the yagi, it quieted right down and the
>> vertical was useless. Both were dc grounded.
>
>Tom-
>
>I have heard others comment about stacked beams, noting the upper one is
>noisier. I wonder if this effect is simply static discharge as from a
>spike used for lightning protection. That is, does an antenna always
>suffer higher noise than when protected by a "spike" mounted above it?
>
>73-
>Fred Roberts, W6TKV
>Riverside, CA
This is why (besides not wanting to be a light source during
transmit) some of the military HF array elements have a smooth
spherical "toilet bowl float" treatment at the open end of the
elements. Sort of a larger version of the ordinary car antenna
ball. Probably isn't a bad idea to provide a _different_ place
for corona to form on the tower though. One that isn't attached
to the receiver feedline.
73, Eric N7CL
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|