[Moon] Excel spreadsheet for calculating a parabola

[Máximo EA1DDO_HK1H]

And one more thing.

Those calculations are always refereed to zero, the starting point located at focus. But depending on the mechanic solution used, that zero point is moved away from the actual focus point.

So, you need to remember to keep always the zero starting point at focus. If you move mechanical pieces away from focus, you need to keep the profile, or modify it.


For example, if your central support for the ribs is adding 20cm separation from one rib to his opposite, then you need to remove 10cm from profile calculation (zero to 10cm), and start the rib on 10cm point calculation.

You can´t just move the ribs away, that will change the focus point.


Am I correct?


73, Maximo

________________________________
De: Moon <moon-bounces at moonbounce.info> en nombre de Peter Blair via Moon <moon at moonbounce.info>
Enviado: martes, 7 de agosto de 2018 11:36
Para: Conrad Farlow; Ingolf, SM6FHZ
Cc: moonbounce_info
Asunto: Re: [Moon] Excel spreadsheet for calculating a parabola

Conrad, if you want to build a really accurate dish then dont forget to
allow for the thickness of the covering in the Y dimension of Ingolf's SS.
So if you use 1mm x 6mm mesh for example then the mesh thickness will be 2mm
because the wires are  laid on each other. If you dont make this allowance
you end up with a non-parabolic error which will affect the phase trajectory
and hence the sidelobe level. If its just for 23 and 13cm then it doesnt
really matter but above that it will be noticeable.
GL 73 Peter G3LTF

-----Original Message-----
From: Conrad Farlow via Moon
Sent: Tuesday, August 07, 2018 11:36 AM
To: Ingolf, SM6FHZ
Cc: moonbounce_info
Subject: Re: [Moon] Excel spreadsheet for calculating a parabola

Wow that was quick - thanks!


73


Conrad PA5Y

________________________________
From: Ingolf, SM6FHZ <ingolf.fhz at gmail.com>
Sent: 07 August 2018 12:35:15
To: Conrad Farlow
Cc: moonbounce_info
Subject: Re: [Moon] Excel spreadsheet for calculating a parabola

Hi Conrad.

Got one here:

http://www.2ingandlin.se/Dish.xls

It is from this page:

http://www.2ingandlin.se/engineering.htm

GL!

73 / Ingolf, SM6FHZ


2018-08-07 12:29 GMT+02:00 Conrad Farlow via Moon
<moon at moonbounce.info<mailto:moon at moonbounce.info>>:
Does anyone have a spreadsheet for plotting the profile of a parabolic dish?
A set of x,y values is all I need versus f/D. I can do it myself but if
something already exists it saves a little time.


73


Conrad PA5Y
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--
Ingolf, SM6FHZ
http://www.2ingandlin.se/SM6FHZ.htm
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