Re: calculation of a waveguide

Rostislav Marinyak schrieb:

> Hallo Christian!
>          At me some technical questions to you were accumulated.
> 1)       I have primefocus a mirror 1.2m, made from aluminium by
> technology of
> hydroexplosion. If his surface to polish, whether quality of his work
> will
> be improved?
> 2)       How correctly to calculate the sizes feeds and waveguides for
> convertors of C-band and Ku-band for primefocus  aerial?
>          Thank, Rostislav.

Do not polish a dish, because if he gets too shiny, he will reflect the
sunlight and the result is a ball from plastic, which was been a part of
the coaxial-cable, all plastic-parts of the feed or polarizer and some
other materials.

The inner-hight of a waveguide is 1/2 lambda of the highest frequency.
The width is one lambda of the highest frequency. The lower cut-off
frequency of the waveguide starts if the 1/2 lambda of this lower
frequency is greater than the 1/2 lambda (hight) of the highest
frequency. A little bit difficult to explain.
Lets calculate a standard WR75 feed for the ku-band:
The operating range is 10 to 15 GHz
1/2 lambda for the height is 0.953 cm
the width is 1.906 cm
the lower cut-off frequency is 7.87 GHz, because a 1/2 lambda is 1,905
cm and will rise if you go down in frequency.

The standard value for C-band (WR229) is:
operating range: 3.3 to 4.9 GHz
inner-hight of the waveguide: 2.908cm
inner-widht of the wave guide: 5.816 cm
cut-off frequency: 7.869 GHz

Christian Mass (Dr.Dish)
Senior-Editor of TELE-satellite International
Producer of drdish@tv

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