Adapting an astra/hotbird monoblock to a 100 cm dish

[rodscha]

I d like to get a 100 cm dish instead of my present 78 cms which works fine with a 6° monoblock.
How will the 6°spread ,for78 cms,be affected by this larger 100 cms dish?
Which would be an example of multi sat reception adapted to 100 cms?
7w,5w,9E,13E,16E,19E would me my targets.
Also 26E/28E if feasible.
Rotors won t work,too much wind!

 

[Analoguesat]

The monobloc spread will be narrower on a bigger dish.

 

[rodscha]

Thank you very much,and a happy Easter!
so,instead of 6° for astra/hotbird,how much would it be ?
Lat 43/long 2,33E

 

[a33]

How will the 6°spread ,for78 cms,be affected by this larger 100 cms dish?

This would be 6 * 78 / 100 = 4.7 degrees, assuming that the opening angle or f/D ratio equivalent of the two dishes are equal.

A bigger dish will have a smaller beam width, which implies that a bigger dish is less forgiving for mismatches in monoblock distances.

A 100cm dish often allows to use separate LNBs, on a multifeed rail. Is that not an option, for you?

Greetz,
A33

 

[rodscha]

yes sure I m considering the idea
May a 4°monoblock work on 13&19?
adjusting for nearness of dish possibly?

 

[Lazarus]

Is it not the case that adjustable Monoblocks are now available, with a spread up to 12deg?

Edited to add: Summat like this Adjustable monobloc LNB 3° 4.3° 6.2° 9° Single Cahors

 

[a33]

May a 4°monoblock work on 13&19?
adjusting for nearness of dish possibly?

4°monoblock, 6°monoblock, that is all relative to the width of the dish, and f/D ratio (equivalent). These latter values are often not mentioned.
A 4°monoblock on a 60cm dish would function as a 6°monoblock on a 40 cm dish (with equal f/D-ratio(equivalent)).
So what kind of 4°monoblock do you mean?
And how would you "adjust" something, on a monoblock? Apart from what Lazarus wrote? (The "spread" can easily be made wider, but hardly smaller...)


The crucial factor of a monoblock is the distance between the phase centers of both feedhorns of the monoblock. Or, the same value: the distance between the center of the two 'tubes' of the monoblock.
That distance must match the angular distance between the two satellites from your location, and the effective focal length of your dish. Accounting for Beam Deviation Factor, of course.

Multifeed skew can be calculated; I've a pretty exact calculator nowadays.

Greetz,
A33

 

[rodscha]

it seems what I need is adjustable LNBc
Moreover the dish is standing near my sitting room,so I can easily fiddle whenever I feel to try some less usual sat,and retune to basic 9//13/16/19
16 not being a priority.

 

[Channel Hopper]

it seems what I need is adjustable LNBc
Moreover the dish is standing near my sitting room,so I can easily fiddle whenever I feel to try some less usual sat,and retune to basic 9//13/16/19
16 not being a priority.

Or a second dish.

 

[rodscha]

Makes sense ,I ll still have my 85cms on the side!

 

[LeBelge]

Multifeed skew can be calculated; I've a pretty exact calculator nowadays.

My dish is skewed without any calculator

45°E - 42°E - 39°E - 33°E - 28°E - 24°E

p.s.
my brain is capable enough to imagine how to manage, without 5 years studying at university to be an engineer

 

[LeBelge]

it seems what I need is adjustable LNBc

Here are the LNBs that you need

 

[AtOM13]

I d like to get a 100 cm dish instead of my present 78 cms which works fine with a 6° monoblock.
How will the 6°spread ,for78 cms,be affected by this larger 100 cms dish?

Yes you can, I used before a 6° monoblock Sedea on my Triax 100cm without problem, you won’t have the same quality with using two lnb separately but it’s ok. Now my setup is Thor/Hotbird/Astra with 3 LNB on my Sedea 80cm

 

[a33]

Yes you can, I used before a 6° monoblock Sedea on my Triax 100cm without problem, you won’t have the same quality with using two lnb separately but it’s ok.

And another example:
A triple LNB 19-23-28E, designed/meant for a 60cm dish (triax64) in the Netherlands/Belgium, actually gives better reception on a 70 cm dish (triax78).
Alignment must be done very precisely, though.

Greetz,
A33

 

[rodscha]

@ A33 Good morning!
i am 1000kms more south,Carcassonne (100ks from Spain as the crow flies)
,so I won' t be able to do that.
But it looks very interesting indeed!

 

[rodscha]

Yes you can, I used before a 6° monoblock Sedea on my Triax 100cm without problem, you won’t have the same quality with using two lnb separately but it’s ok. Now my setup is Thor/Hotbird/Astra with 3 LNB on my Sedea 80cm

This looks really interesting!

 

[Beli1910]

Look here:Triax 90 multifeed 39E-4-5W Diqec 10/1 @beli1910 - Oprema za praćenje satelitske TV - Satelitski Forum - SF
In this way, I made a multifeed on a triax antenna (39E-4W) in 2013. Material-universal multiholders pro. I made a sino-reduced Clark path after calculation from the antenna's plot point to the central lnb. and then making a rail or support for lnb-e.