New Dish Design

Rob

A few month's ago someone showed a picture of a new type of dish with a round metal plate which reflected the signal onto the lnb which was facing away from the dish but towards the round metal plate.
It was supposed to increase the signal strength for a 80cm dish (I think).

Can anyone remember where this thread is, as I can't find it anywhere.
And also has anyone any comment on this dish !

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rolfw

It isn't new Rob, in fact they aren't really made nowadays by many manufacturers, if any at all. Search for Gregorian or Fibo and several threads will come up, there should be some pictures in the Pictures of members' systems thread as well.

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PaulR

It's not a new design. Search for Gregorian and you should find the post.

There's another double reflector design called Cassegrain but is less common, try that if Gregorian doesn't work.

EDIT. Damn, Rolf beat me again. Must have been by seconds only this time though.

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PaulR

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Rob

Bloody hell I thought it was a couple of months ago and it was only last week, must be getting old.
Posted by tkean1952 from Germany a week ago.

It was the Kreiselmeyer Superfocus I was thinking of, which is supposed to make a 85cm act like a 110-120cm. Think this is a load of bull, but does anyone else have any idea's as I would love to admit that I'm wrong.

Attached Images

kreiselmeyer_superfocus.jpg (69.9 KB, 36 views)

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rolfw

They do perform well compared to a standard offset, but not that well.

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Channel Hopper

Cassegrain is a term used for prime focus dishes, Gregorian for offset.
And the toroidal design for the multi LNB Wavefrontier and Vertex prototypes

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boxnut

you will find that the performance of a dish is a function of it's gain and f/d ratio. 2wit:gain increases with reflector area,and beamwidth narrows with increased f/d ratio. folding back the signal with a secondary reflector would not affect the signal quality. if anything it may introduce additional e-lobe interferance, and reverse the polarity of circular polarization.
'boxnut'

Rob

You took the words right out of my mouth boxnut.

But has anyone tried them ???

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Jeff_19341

Try a search for Gregorian antennas, at least one other member uses/used them. It might be under the name Fibo dish.

rolfw

LOL, I get this strange feeling of Deja vu JuMbuCk.

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BGonaSTICK

Wow, yes of course

Good point, not that it will have much effect for most of us.

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johnsattuk

Pic. looks identical to a Fibo dish, its amazing how many aliases they had

Rob

Think your right there John, Well so far we have a Gregorian, a Fibo, and a Kresielmeyer Superfocus and they are all the same dish.
Don't know how many other names it goes by, I just want to know if it is worth buying one.

Attached Images

kreiselmeyer_superfocus.jpg (69.9 KB, 9 views)

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rolfw

Not the brand name of a dish, Gregorian is the name given to the design, originally taken from the telescope design using a concave secondary reflector Origins of Gregorian and Cassegrain, Cassegrain actually applies to a similar arrangement, but using a convex reflector

Using those criteria, the Fibo and copies would all be Gregorian and the Wave Frontier a Cassegrain.

You'll probably find that there weren't many manufacturers making these dishes, most being a branded version of the the main manufacturer, a bit like nowadays really.

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BGonaSTICK

Hey, thanks for that link m8. Not really into astronomy (other than our yearly outing to The Observatory Science Centre, Herstmonceux) I found that very interesting. Especially the naming punchline!

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johnsattuk

I am a little biased, since I have 3 Fibo dishes, ( one 'Fibo', one 'Grundig' & one 'Philips' ) .

'Worth it' means different things depending on the criteria, and individual cicumstances and desires.

Least cost for a given size or performance. These are not necessarily the same thing because of the differences in the results that people get from different manufacturers, and 'one mans meat' etc. Also results do seem to vary quite a bit, depending in the overall setup, ie. which LNB, feedhorn and so on.

My S/H 'Fibo' dishes have all cost me more than similar new dishes that I have bought the past, but the 'Fibo' dish is a integrated system, from mount to feed horn, with extensive use of intricate diecastings. As a retired engineer the general design and manufacture of these dishes make them desireable and worth it to me.

I don't 'know' if they perform better than any other properly set up dish, opinions vary, and others have their own favourites, but the 'Fibo' is designed as a complete system with the main reflector, sub-reflector, feedhorn, and mounting arm all matched to one another, which I think must be a good thing.
I of course think that mine does.

I have found my 'Fibo' dishes very easy to set up, the mounting system is an integral part, with accurate clear scales on the diecasting.

Good luck with whatever you buy