[TowerTalk] Field Strength comparison

[Stan Stockton]

I’m missing something.  How do I get 180 out of 2 * 900/80?

Thanks, Jim.

Stan

Sent from my iPhone

> 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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