[SBE] NEC/4 Modeling

[Dave Dybas]

Paul,

We typically use the 120 radial 1/4 wavelength ground system under a tower as it provides a "near ideal" ground.  As 4NEC2 allows for an "ideal ground" I usually use that for my modelling.  This provides reasonable values of tower base impedance.

 Additionally 4NEC2 also allows for a 2nd ground system at a distance from the tower....this 2nd ground can be set to begin at 1/4 wavelength from the tower...which is where the 120 ground radials typically end.  The conductivity of the 2nd ground can be set to that of your towers neighborhood.  This conductivity will be used to determine your signal strength at a distance. 

Dave Dybas
dd92251 at aol.com


***************************************************


-----Original Message-----
From: Paul Christensen <pchristensen at ieee.org>
To: sbe member discussion mail list <sbe at sbe.org>
Sent: Thu, May 17, 2012 4:34 pm
Subject: Re: [SBE] NEC/4 Modeling


Yes, NEC-4 allows for close-earth modeling of varying soil conductivity.  
 
Paul
 
 
 
 
 
====================================
Paul Christensen, CPBE CBNT 8-VSB AMD
LAW OFFICE of P. B. CHRISTENSEN, P.A.
3749 Southern Hills,  Jacksonville, Florida 32225
Office: (904) 379-7802    Facsimile: (904) 212-0050
pchristensen at ieee.org


----- Original Message ----- 
From: Adrienne Abbott 
To: 'sbe member discussion mail list' 
Sent: Thursday, May 17, 2012 4:53 PM
Subject: Re: [SBE] NEC/4 Modeling



Does all this technology take ground conductivity into account? That could impact your results more than ground placement

Adrienne
 
 

From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Paul Christensen
Sent: Thursday, May 17, 2012 1:30 PM
To: sbe member discussion mail list
Subject: Re: [SBE] NEC/4 Modeling

 

Hi Cris,

 

I'm trying to get accurate base Z results as well as surface wave field strength predictions.  Within 4Nec2 is a fast radial wizard, but it does not allow for changing ground placement, albeit the effect may be small.   In any case, creating a buried system is easy enough through the geometry builder utility.  The examples would be used to ensure that I've done the job correctly.  

 

I've had this discussion with Arie Voors, 4Nec2's developer, as well as Jerry Burke at LLNL.  The consensus is to create a modeled radial system for best results.   Ben Dawson suggested J.L. Smith's examples, so I can start there.

 


Regards,

Paul




===================================
Paul Christensen, Esq.
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3749 Southern Hills
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Office: (904) 379-7802
Facsimile: (904) 212-0050
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----- Original Message ----- 

From: Cris Alexander 

To: 'sbe member discussion mail list' 

Sent: Thursday, May 17, 2012 4:12 PM

Subject: Re: [SBE] NEC/4 Modeling

 

Is this for AM broadcast? If so, set the environment for ground plane and forget about trying to model a buried ground medium.
 

______________________________
W.C. Alexander, CPBE, AMD, DRB
Crawford Broadcasting Company
Denver, CO
(303) 433-0104 Tel.
(303) 433-0905 Fax.

 

From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Paul Christensen
Sent: Thursday, May 17, 2012 1:39 PM
To: sbe member discussion mail list
Subject: [SBE] NEC/4 Modeling

 

Looking to validate the buried radial parameters of a .NEC input file for a non-phased, single monopole radiator.  I've been using the geometry builder utility within 4Nec2 software, but I want to confirm radial depth results as well as source/load parameters.  If anyone has an input file to share, it would be very much appreciated.  I have J.L. Smith's book on order and will use his examples as well.  Thanks!

 

Regards,

 

Paul

 

 

====================================
Paul Christensen, CPBE  CBNT  8-VSB  AMD
LAW OFFICE of P. B. CHRISTENSEN, P.A.
3749 Southern Hills,  Jacksonville, Florida 32225
Office: (904) 379-7802    Facsimile: (904) 212-0050
pchristensen at ieee.org

 


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