[TowerTalk] Fwd: Fwd: Pseudo-Brewster Angle

[Hans Hammarquist]

 Gene,

Try en.wikipedia.org/wiki/Brewster's_angle . You find a rather complex explanation there. 

An easy explanation is that the Brewster angle is about 56 degree for glass with a refraction index of about 1.5. The angle increases closer to 85 degree for water with the refraction index (I believe) 9. The index varies in soil due to variations in water content etc. The index varies also in there is magnetic material in the soil which make rather hard to predict exactly where a vertical polarized radio wave will be absorbed.

It is commonly known that if you place your vertical antenna in water (like on a boat) or in swamp area your signal will come out strong.

Now, how will the Fresnel zone interfere with this?

Hans - N2JFS

 

 

-----Original Message-----
From: Gene Smar <ersmar at verizon.net>
To: hanslg <hanslg at aol.com>; towertalk <towertalk at contesting.com>
Sent: Wed, Mar 2, 2016 8:14 pm
Subject: Re: [TowerTalk] Fwd:  Pseudo-Brewster Angle

Kris et al:
 
     I've often wondered the same thing about John's books:  Where did he get all the equations?  I don't recall seeing references listed.
 
 
73 de
Gene Smar  AD3F
 



On 03/02/16, Hans Hammarquist via TowerTalk wrote:


Partic,

It's the same Brewster's angle as you worked with building a LASER, it's just that your dielectric surface is now must more undefined. A flat piece of glass will not reflect at one specific angle while the soil has a much wider range of dielectric constant and not necessary such a flat surface.

I guess you didn't have to make the LASER cow proof either.

Hans - N2JFS





-----Original Message-----
From: Patrick Greenlee patrick_g at windstream.net>
To: towertalk towertalk at contesting.com>
Sent: Wed, Mar 2, 2016 5:47 pm
Subject: Re: [TowerTalk] Pseudo-Brewster Angle


Gee, I hadn't heard the term Brewster's angle in decades, not since I 
was an undergrad physics student building tunable liquid dye LASERs as a 
special project for credit.

Patrick NJ5G

On 3/2/2016 9:50 AM, Mike & Becca Krzystyniak wrote:
> What about shorting together the circumference in a ring?
> How does that affect the angle?
>
> MK
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of N5KM
> - Kris
> Sent: Wednesday, March 02, 2016 12:07 AM
> To: towertalk at contesting.com
> Subject: [TowerTalk] Pseudo-Brewster Angle
>
> Reading the thread about an effective radial system got me thinking about
> the pseudo-Brewster angle of a 1/4 wl vertical antenna. As strictly a mental
> exercise, I calculated how much radial wire would be needed for an 80m
> vertical Fresnel zone that results in a low (1-2 degree) pseudo-Brewster
> angle. Assuming 120 radials of 5 wavelengths each that comes to 30 miles of
> wire on a parcel of at least 122 acres.
>
> The tips of the radial will be 68 feet apart. This raises the question is
> this too far apart to affect the pseudo-Brewster angle? Devoldere says yes
> (Low-Band DXing, 3rd ed.). He says they need to be no more than .05 wl (13
> feet) apart.
> The return
> currents will be nearly entirely collected by the close-in parts of the
> radials. So that's not an issue. John doesn't show the math or other
> analysis that leads to the
> .05 wl figure so I'm not entirely convinced it's needed. However, if true,
> that would require an additional 60 miles of wire.
>
> Kris N5KM
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