Towertalk
[Top] [All Lists]

Re: [TowerTalk] Field Strength comparison

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Field Strength comparison
From: "Lux, Jim" <jim@luxfamily.com>
Date: Sat, 4 Sep 2021 18:32:09 -0700
List-post: <mailto:towertalk@contesting.com>
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@gmail.com> wrote:


Sent from my iPhone

Begin forwarded message:

From: "Lux, Jim" <jim@luxfamily.com>
Date: September 4, 2021 at 5:58:44 PM CDT
To: TowerTalk@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



_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk


_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
<Prev in Thread] Current Thread [Next in Thread>