Signal difference between Astra/Hotbird with monoblock

keenite

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Hello everyone,
I have a monoblock twin [Astra A; Hotbird B].
When I adjust the Hotbird signal via B I cannot get a signal in excess of approx. 47%, whereas Astra's signal is around 90%. I realize these numbers are relative. To the naked eye the monoblock appears to be level with the ground.
With my old monoblock I was getting a somewhat weaker signal on Astra, but considerably stronger signal on Hotbird. I have exchanged the cables from the two LNBs, but this did not change the results.
Given the theoretical signal strengths according to Lyngsat for my location (Hotbird ca. 51/52; Astra ca. 51) I would have expected to have similar signal strengths.
Any ideas?
TIA for your help.
 

keenite

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PS:
Monoblock model "Opticum LMTP-04H-AH Premium Monoblock Twin LNB 0.1 dB"
 

Lazarus

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The Monoblock requires rotating, in order to fine tune the Elevation of the offset Bird: This is achieved by rotating the captive head so that the offset head is raised (or lowered, depending upon which Satellite is the focus). Just a few degrees should provide improvement.

Like all else, the result will be a compromise as adjusting the offset alters the skew for the focal bird.
 

keenite

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Thanks,
I'm assuming that Astra is the focal bird. Looking at the LNBs from the back of the dish (i.e. you can see the receiving surfaces of the LNBs), the monoblck is mounted via the right LNB, with the other 'hanging' to its left.
Where can I found out what theoretical skew is required for my location in Berlin, Germany.
 

Lazarus

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You don't need the theoretical skew as your rotational position is going to be a compromise ............... this is a job which is easily, quickly and best achieved by simple experimentation: I suggest you first try with the F connector at about 7 o'clock.


Hopefully it will make a big difference to your offset Satellite and it's possible you'll get further gains if you subsequently make fine adjustments to dish alignment: I have installed two Monoblock equipped dishes and found an iterative approach pays dividends. Doesn't take long. Minutes, maybe.


Edit: Forum Software keeps removing my paragraph breaks upon editing ................

Edit: Now sorted.
 

keenite

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I'm not sure what you mean by "F connector at about 7 o'clock"? Right now the F-connectorS are straight up and down, i.e. the LNB has not been turned in either direction. Should the 'hanging' LNB be turned such that it is lower than the centered one?
 

Lazarus

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Hanging down = Connector at six o'clock.

When looking from LNB towards dish, rotate the Monoblock in its clamp a few degrees so the F connector moves clockwise to roughly seven o'clock. See what happens.

The rotation required is only small - so just experiment. You can always return it to the starting position if you see no worthwhile change.

Required Elevation for Astra 1 is lower than for Hotbird, so the general principle of reflection in terms of Satellite dish angles means the the LNB head for Astra 1 should be marginally higher than the Hotbird one.
 

Lazarus

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Just to clarify - the main point of this exercise is to correctly cater for the Elevation of the offset Bird - it's just that the physical act of doing so is akin to setting skew for a single LNB dish.

The difference in theoretical skew itself is trivial when compared with the effect of overshooting (or undershooting) the required Elevation for the offset Satellite.

ie For a single LNB dish, Elevation alignment is achieved by raising/lowering the dish bracket but for a dish with a Monoblock, Elevation alignment for the offset Satellite is achieved by rotation of the Monoblock (There's no other way of doing it).

The likely reason why your Hotbird results are iffy is because, with the Monoblock level, you are effectively trying to receive it using the same Elevation as for Astra 1 - which won't work very well!
 
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