[TowerTalk] Optimum yagi stacking distance

[donovanf at starpower.net]

Larry,

Unless the terrain in front of your antenna is sloped more than two or three degrees for at least several thousand feet, your antenna will work very well at 115 feet.  

In two or three years -- when we have significant sunspot activity -- you may find some occasions when its too high on 10 and 12 meters but for the most part its going to work much better than your 70 foot tower ever did.

73
Frank
W3LPL

---- Original message ----
>Date: Sat, 19 Jan 2008 20:35:56 -0500
>From: Larry DiGioia N8KU <towertalk at longwire.com>  
>Subject: Re: [TowerTalk] Optimum yagi stacking distance  
>To: towertalk at contesting.com
>
>OK, you guys are starting to worry me.
>
>I just bought 4 more sections of Rohn 45 to get my 70-footer up to 110' 
>in preparation for putting up my dream antenna - an M2 10-30LP8 Log 
>Periodic. 115' seemed like a good height for this antenna, is it 
>actually possible this is TOO high?
>
>My only goal is WAZ on 30 through 10m. I am not a contester.
>
>Larry N8KU
>
>Cqtestk4xs at aol.com wrote:
>> In a message dated 1/19/2008 4:15:10 P.M. Greenwich Standard Time,  
>> gdslagel at yahoo.com writes:
>>
>>
>> I've  been using the HFTA software to try and get an
>> idea of the optimum distance  to stack a couple yagis
>> for best performance.  I'm stacking  10/15/20
>> tribanders for increased performance.  I was  really
>> surprised that on most bands the optimum performance
>> seems to be  with them separated by only about 10'...
>> for instance 65' and 56'!  I  expected it to be more
>> like 20' to 30'!  
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> There is a caveat somewhere about this from N6BV.  It is something  
>> like...when using very close spacing (like 10 feet) for HF antennas, the HFTA  program 
>> by N6BV will give false results.
>>  
>> If your top antenna height is going to be 65 feet, it would be in your best  
>> interest to have the other at 32 feet if you are going to operate all  bands.  
>> It is a little too close for 20 but should do well on 15 and  10...assuming 
>> you are running a garden variety tribander of normal boom  length.
>>  
>> The HFTA is a wonderful tool if used with caution.  Out here in a  VERY 
>> mountainous terrain N6BV's program was invaluable in designing my  stacks.  I 
>> wanted to stack three KT36XAs but I found that with my terrain  anything higher 
>> than 90 feet was a total dud for 20 through 10 meters.  The  result will be 
>> 90/56/29.  But, that was an optimization for my QTH.  
>>  
>> I too was amazed with how much gain I could achieve with spacing of 10  feet, 
>> until I read the instructions for HFTA.  Generally you will need  a minimum 
>> of .5 wavelength for the stacks to start to play and from what I've  read, 
>> .65-.75 plays about the best.  Of course this depends on boom  length.  
>>  
>> I hope this helps.
>>  
>> Bill KH7XS/K4XS
>>
>>
>>
>>
>>
>>
>>
>> **************Start the year off right.  Easy ways to stay in shape.     
>> http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489
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>>   
>
>-- 
>Larry  N8KU
>
> l o n g w i r e . c o m
> HF - DX - CW - Digital
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