[SBE] NEC/4 Modeling

[Bob Reite]

I had pretty good results with NEC-4 predicting what a cell phone tower 
would do to the base Z of a 1/4 wave vertical on 1280 KHz.

On 5/17/12 11:22 PM, Paul Christensen wrote:

> Cris,

> Good info. I've also noticed a high degree of computed Z variability

> under both NEC-2 and NEC-4. It seems the computed Z for free space

> designs (e.g., Yagi) model much more accurately than ground-dependent

> radiators.

> 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 <mailto:pchristensen at ieee.org>

>

>     ----- Original Message -----

>     *From:* Cris Alexander <mailto:crisa at crawfordbroadcasting.com>

>     *To:* 'sbe member discussion mail list' <mailto:sbe at sbe.org>

>     *Sent:* Thursday, May 17, 2012 5:48 PM

>     *Subject:* Re: [SBE] NEC/4 Modeling

>

>     Okay, Paul. I understand.

>

>     I’ve done a ton of modeling over the years and in my experience, the

>     far field E-field differences between a modeled radial system and a

>     perfect ground plane are hardly worth all the trouble to model it

>     all. We’re talking fractions of a dB at 1 km, and the base Z

>     predictions are certainly in the ballpark if not the infield. That

>     being said, impedance prediction is probably the weakest function of

>     NEC/MN.

>

>     I can heartily endorse J.L.’s book and in fact the equations therein

>     were the basis for my own MN program (ACSModel).

>

>     *______________________________*

>

>     *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 2:30 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.

>     LAW OFFICE of PAUL B. CHRISTENSEN, P.A.

>     3749 Southern Hills

>     Jacksonville, Florida 32225

>     Office: (904) 379-7802

>     Facsimile: (904) 212-0050

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>         ----- Original Message -----

>

>         *From:*Cris Alexander <mailto:crisa at crawfordbroadcasting.com>

>

>         *To:*'sbe member discussion mail list' <mailto:sbe at sbe.org>

>

>         *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>

>         [mailto:sbe-bounces at sbe.org]

>         <mailto:[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 <mailto:pchristensen at ieee.org>

>

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