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id xma016788; Wed, 13 Aug 97 10:42:04 -0600
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To: k6se@juno.com (Earl W Cunningham), philk5pc@connect.net
From: John Brosnahan <broz@csn.net>
Subject: Re: TopBand: Re: Rohn Tower on 160m
Cc: topband@contesting.com
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At 04:15 AM 8/13/97 EDT, Earl W Cunningham wrote:
>On Tue, 12 Aug 1997 12:38:35 -0500 philk5pc@connect.net (Phil Clements)
>writes:
>>I am planning the installation of a Rohn 25 tower as a 1/4 wave 160m
>>vertical. There will be an adjustable 10' aluminum mast on top to
>resonate the
>>tower on 1830 khz.
>>
>>How tall must the Rohn 25 be to be resonant?
>>
>===========
>Hi, Phil,
>
>I couldn't resist using a NEC-based program (ELNEC) on this one. Rohn 25
>is 12.5" on a side. To simplify things, I substituted a 12.5" diameter
>conductor for the tower and assumed the 10' mast diameter is 2".
>
Because Rohn 25 comes in 10' lengths, this posed somewhat of a dilemma --
>using 120' of tower requires 13' of 2" mast above it (total height =
>133') to resonate at 1830 kHz.
Because of the overlap between sections Rohn actually stacks
at about 3.5 inches less than 10ft. Not much until you stack a
ozen sections and end up 3 ft short!
73 John W0UN
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