[TowerTalk] Field Strength comparison

[Lux, Jim]

On 9/4/21 6:02 PM, Stan Stockton wrote:
> I’m missing something.  How do I get 180 out of 2 * 900/80?
>
> Thanks, Jim.
>
> Stan
>
> Sent from my iPhone

You're right.. brain freeze. But 22.5 meters seems awfully close.   2 
D^2/lambda is the equation - 2 * 30*30/80 = 1800/80 = 22.5 meters

Granted that's for "directive antennas" - Something weird (maybe it's 
invalid for antennas that are "smaller than a wavelength") -


>> On Sep 4, 2021, at 7:30 PM, Stan Stockton <wa5rtg at gmail.com> wrote:
>> 
>>
>> Sent from my iPhone
>>
>> Begin forwarded message:
>>
>>> From: "Lux, Jim" <jim at luxfamily.com>
>>> Date: September 4, 2021 at 5:58:44 PM CDT
>>> To: TowerTalk at contesting.com
>>> Subject: Re: [TowerTalk] Field Strength comparison
>>>
>>> On 9/4/21 3:36 PM, Stan Stockton wrote:
>>>> How far away (minimum) should a receive antenna be located if you wanted to accurately measure the difference between a couple of vertical arrays - let’s say, for example a 4 Square and a single vertical.
>>>>
>>>> Thanks… Stan, K5GO
>>> The traditional guide line for antenna ranges is 2 D^2/lambda, where D is the diameter of the antenna.  That has to do with the phase difference from a plane wave being small enough that the gain isn't significantly wrong (I can't remember if it's 0.1 dB or what, and I'm too lazy to calculate it now).
>>>
>>> For a 80 m foursquare, it's roughly 30 meters across (1.414 * 20m) so 2 * 900/80 = 180 meters away
>>>
>>>
>>>
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