[TowerTalk] stacking logs

[Jack KZ4USA]

Any one have a good  large LPDA model that would work in NEC- WIN Plus+ ?


Jack
KZ4USA
Bradenton, Florida


----- Original Message ----- 
From: "Steve, W3AHL" <w3ahl at att.net>
To: "Tower and HF antenna construction topics." <towertalk at contesting.com>
Sent: Sunday, January 24, 2010 3:05 PM
Subject: Re: [TowerTalk] stacking logs


> There are two reasons to stack yagis or LPDA's:
>
> 1.  To increase gain by using a phased array.  Maintaining a specific
> wavelength spacing is important.
>
> 2.  Taking advantage of the different take off angles that antennas at
> different heights have, due to their interaction with the ground. 
> Depending
> upon the ionospheric conditions, the band, the distance between stations,
> etc. sometimes a lower antenna is better than a higher antenna.  Often the
> antennas can be switched so that all, any two or only one antenna is 
> active.
> This is commonly called "space diversity".  Spending an hour with a 
> program
> such as HFTA will provide some insight into why stacked antennas are the
> mainstay of contesters.
>
> Steve, W3AHL
> ----- Original Message ----- 
> From: "jim Jarvis" <jimjarvis at optonline.net>
> To: <towertalk at contesting.com>
> Sent: Sunday, January 24, 2010 2:42 PM
> Subject: Re: [TowerTalk] stacking logs
>
>
>> OK,  I vowed not to add further to this thread.    I lied.
>> Curiosity has the better of me.
>>
>> Where the logs are stacked horizontally, they would seem not
>> to be ideally spaced for vertical angle pattern,  over frequency.
>>
>> The installation on the DX eng'g website...  N9IN or wherever it was...
>> has the
>> logs at 44, 74 and 116 feet.   That's a 30' and 42' spacing between the
>> pairs,
>> and 72' between top and bottom.    There may be some frequency dependent
>> relationship in this spacing, but it isn't falling out in my feeble 
>> brain.
>>
>> The spacings don't work out with any of the free-space pattern spacings
>> with which I'm familiar.
>> Maybe modeled over ground, there's some sense there?
>>
>> In any case, if anyone is able to explain the concept,  I'd be interested
>> to hear it.
>>
>> N2EA
>>
>>
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