For a given size which is better, parabolic or offset?

A

Artist 2004

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My Satellite Setup
GoldMaster 7400 CIM 2MB with Kaon board 12.03.a5. Technomate 1000, Technomate 5200 USB.
Two 80cm offset dishes.
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West coast, Turkey
#1
A shopkeeper told me that a 150cm offset dish gives the same reception as a 200 cm parabolic. Is this true?
 
rolfw

rolfw

Believe it when I see it Admin.
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Technomate 5402 HD M2 Ci, DM7000s, Transparent 80cm Dish, Moteck SG2100 DiseqC motor, lots of legacy gear. Meters: Satlook Digital NIT, Promax HD Ranger+ spectrum analyser.
My Location
Berkshire
#2
I doubt whether a 1.5m offset would out perform a prime focus of simialr quality, the only disadvantage of the prime focus being slight shading of the dish by the LNB and support arms.
 
dig deep

dig deep

Prince of Birthdays
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#3
Every BIG dish is gregorian so I think I bet my "dollar" on Rolfw´s answer
The offset is easier to mount on a wall that is a good reason for using them, not that they are better in any other way:cool:
 
A

Artist 2004

Anatolia correspondent
Messages
252
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0
My Satellite Setup
GoldMaster 7400 CIM 2MB with Kaon board 12.03.a5. Technomate 1000, Technomate 5200 USB.
Two 80cm offset dishes.
My Location
West coast, Turkey
#4
Thanks, both. While I've got your attention, what is the convention for stating dish size for an offset dish? My "120" cm dish is something like 112cm tall and 105 cm wide...
 
S

spiney

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Pace 2200 Sky digibox with ftv card, Comag SL65 FTA sat receiver, 40cm Sky minidish, Setpal terrestrial receiver (for free uk tv only!).
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Midlands
#5
If possible, then an offset dish would always be better. Because, with prime focus dishes (including Cassegrain, etc), various bits "block" part of the radio "beam" falling on the reflective surface.

This effect varies, with dish type, so no "general formula" is possible.

As dishes get bigger, the offset type doesn't have enough mechanical stability, ie, the long lnb pole and dish surface would flex too much, putting the lnb "off focus".
 
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