TopBand: Rohn SSV as 160M antenna?

[km1h @ juno.com]

On Wed, 20 Aug 1997 12:39:56 +0000 w8jitom@postoffice.worldnet.att.net
writes:
>> Subject:       TopBand: Rohn SSV as 160M antenna?
>> Date:          Wed, 20 Aug 97 11:58:34 +0000
>
>> I am putting up a rhon SSV 100' freestanding tower with #8 bottom
>>section and #4 straight top section. There will be a 6 meter beam on 
>>a 34' boom and a 17' mast out the top.  Has anyone else loaded s> 73 
>>GEO (K0FF)
>
>Hi George,
>
>When a structure tapers to a narrower point at the outer end, it 
>looks electrically shorter and the bandwidth gets narrower. Think of 
>it as a backwards fed discone, with opposite results. 
>
>That's because the distributed capacitance decreases right where you 
>need it most, at the most concentrated area of E-field. You wind up 
>with a long area of antenna with reduced current, and hence reduced 
>radiation.
>
>I have no idea how that will affect your tower, the beam on top 
>will tend to offset the effect somewhat. It would be worth 
>looking at on a modeling program, because you might find (or might 
>not find) a uniform cross section wire cage will help.  
>
>73 Tom

This goes way back to the late 1920's; early 1930's when AM broadcasters
were initially using huge tapered towers. They found that the radiation
patterns were not at the horizon but skewed upwards considerably due to
uneven current distribution. 
Since then AM towers have been uniform cross section. 

73...Carl  KM1H

--
FAQ on WWW:               http://www.contesting.com/topband.html
Submissions:              topband@contesting.com
Administrative requests:  topband-REQUEST@contesting.com
Problems:                 owner-topband@contesting.com