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@longwire.com>
>Subject: Re: [TowerTalk] Optimum yagi stacking distance
>To: towertalk@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@aol.com wrote:
>> In a message dated 1/19/2008 4:15:10 P.M. Greenwich Standard Time,
>> gdslagel@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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