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RimaNTSS

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Hi! Under the influence of another thread I have decided to play little bit more with CM 1.2m antenna, namely to convert it to double-reflector design. All I need is to make set of parts (mostly INOX) which will allow to nicely install Fibo bottom feedarm with the subreflector and feedhorn, or even without Fibo feedhorn to play with standard Ku or C band LNBFs. Feedarm, subreflector and feedhorn from 1.2m Fibo or 90cm Fibo can be used here. Actually, set is almost ready, only sidearms are missing (need to buy some INOX 10mm tubes). At the end of the day I will have 2x CM 1.2m installed shoulder to shoulder, one in usual setup and another one in double-reflector mode and then see which performs better. By theory dual-reflector antenna systems should bring ~10% better performance, side-lobes and X-pol minimized.
 

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Captain Jack

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Beautiful work. Very tidy!
 

Trust

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Last edited:

RimaNTSS

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Also done the feedarms. It is not so easy to find the proper position of the sub.... first I need to tune antenna to some satellite in the normal setup (just main mirror and LNBF in focus). Then, without moving the main mirror, sub should be installed and manually find it's proper position by maximum signal. I've done this procedure several times.... yes, it takes time :confused, but that is fun! :Y
 

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Captain Jack

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Any chance of making this for the 1.8m? :D
 

WHATAGOAL1

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RimaNTSS, you are truly a dish Master
 

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You are very skilled indeed
 

RimaNTSS

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Thanks all!
Any chance of making this for the 1.8m?
The only difference here is the length of feedarms. And, because of the different length the diameter of tubes should be different as well. For 1.2m antenna 10-12mm tubes for side-feedarms , but for 1.8m antennas 14mm tubes are better be used. I will probably do the set for 1.8m CM dish soon to see how it works.
 

RimaNTSS

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Well, there is some difference between 1.2m and 1.8m dishes.... and not only sizes of the mirrors. For 1.8m dish it is more appropriate to use M8 bolts & nuts , but for 1.2m dish M6 is more than enough. Of course, feedarms are in different length and different diameter tubes are used (12mm for 1.2m and 14mm for 1.8m). Other-ways nothing more differs and it is only matter of tuning, adjusting and tests.
 

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samoloko

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very nice Rima,

how much dB did you gain with fibo sub reflector mod on CM 1.8
 

RimaNTSS

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Alex!
Theoretically, Gregorian and Cassagrain design of antenna system performs ~10% better than single reflector system. When I was experimenting with double-reflector systems I felt that performance was a little better (not worse for sure) than same antenna without sub. Another point is it is fun doing such experiments. We are talking about hobby, do not we? :D .
 

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@RimaNTSS - good to hear from you again (not much lately!) :D

How's the health situation in your neck of the "woods"?
 
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