[TowerTalk] Field Strength comparison

[Stan Stockton]

I’m thinking that since 22.5 meters on 80m, for example, would put the RX antenna on top of radials from the closest vertical and it would be way too close.  I would not be surprised if you measured field strength at that distance and then just removed the radials from one of the four verticals plus or minus about 45 degrees in the direction of the RX antenna you would see a dramatic difference in field strength.  Perhaps the radial field at minimum should be included in the diameter which would be about 1.414*66 or about 100m.  That would get you to about 250m which would seem more like it or at least better.

However applying that formula to a vertical dipole with a diameter of one inch… IDK.

Stan
> 
>> From: "Lux, Jim" <jim at luxfamily.com>
>> Date: September 4, 2021 at 8:32:31 PM CDT
>> To: TowerTalk at contesting.com
>> Subject: Re: [TowerTalk] Field Strength comparison
>> 
>> 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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