[Moon-net] 2 D model of Parabola that incorporates an RMS error factor.

Pat Barthelow aa6eg at hotmail.com
Sat Sep 27 17:51:20 CEST 2008


Thanks, Rasto, 

For the reply and the reference Book.  I will have to look for that one.

Perhaps it could be done in two dimensions, just a slice/profile of the 
surfaces through the vertex...  I have the high resolution  (6 millimeter increment, .05 mm accuracy) precision file, 2 D, coordinates,  of the mathematical  surface profiles of Jamesburg, both the main reflector, and the secondary reflector,   and would be interested in studying the affects of errors vs frequency,  on the beam pattern. 
If I could write a realistic program that modifies the profile data set,  to simulate a known RMS surface error, then run in a standard parabolic modelng program to see how a real dish responds compared with the theoretical surface.  We have about .050" RMS errors on the dish.

(By the way, I am very new to this... a good technical background, but no in-depth experience in this application...) 

Thanks, 




All the best,

Pat Barthelow   (916) 315-9271; aa6eg at k6bj.org

Jamesburg Moonbounce Team

http://www.jamesburgdish.org

http://www.greatdanepro.com/Blue%20Bueaty/index.htm





> Date: Sat, 27 Sep 2008 08:34:53 -0700
> From: om6aa at yahoo.com
> To: aa6eg at k6bj.org
> CC: moon-net at list-serv.davidv.net
> Subject: Re: [Moon-net] Parabola Model, Pattern generation;	with Random surface errors
> 
> Hello Pat,
> 
>    I am afraid, that it is not possible to calculate such electrically large structure as is Jamesburg dish antenna (involving also it`s surface deviation) with professional el.mag. modelling softwares as are CST MW Studio , FEKO or HFSS due to huge amount of data. This task must be calculated separately as an independed efficiency coefficient of whole antenna, or must be involved in illumination efficiency coefficient. More about this problem you can find in the book " THE PARABOLOIDAL REFLECTOR ANTENNA IN RADIO ASTRONOMY AND COMMUNICATION" by JACOB W.M. BAARS,  ISBN-10: 0-387-69733-0. In the book are also  some routines written in software package "Mathematica" which you may find useful for your purposes.
> 
>    Sincerely, 
>                      Rasto OM6AA
> 
> --- On Fri, 9/26/08, Pat Barthelow <aa6eg at hotmail.com> wrote:
> From: Pat Barthelow
>  <aa6eg at hotmail.com>
> Subject: [Moon-net]
>  Parabola Model, Pattern
>  generation; with Random surface errors
> To: moon-net at list-serv.davidv.net
> Date: Friday, September 26,
>  2008, 12:46 PM
> 
> Folks: 
> 
> Are there any Antenna modeling programs, within reach of EME enthusiasts ( If
> not them, then avaailable for professional work)  that would allow you to enter
> a fine detail theoretical  surface coordinate database, then have the user apply
> an empirically derived RMS error metric, to the perfect coordinate database,
> generating a representative, as found, surface?   
> 
> Then, based on the real, "lumpy" surface, generate beam patterns, for
> a given frequency.  It would be interesting to see Jamesburg's real pattern,
> both at C band, it's designed frequency, and then pushing it to higher
> frequencies, say, X band, and see how the pattern degrades, based on an RMS
> error which we determined to be in the vicinity of .050"
> 
> 
> 
> 
> 
> All the best,
> 
> Pat Barthelow   (916) 315-9271; aa6eg at k6bj.org
> 
> Jamesburg Moonbounce
> 
> 
> 
> 
>  Team
> 
> http://www.jamesburgdish.org
> 
> http://www.greatdanepro.com/Blue%20Bueaty/index.htm
> 
> 
> 
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