Lnb arm mod

D

dovercat

Member
Messages
28
My Satellite Setup
Televes 1mtr dish (102x113cm, Gain at 11GHz 40.5dB, Beamwidth 1.98degrees)
Televes 0.5dB LNB
(gain 57dB, discrimination 25dB, oscillator stability +/-2MHz, phase noise max-75dBc@10KHz)
Moteck 2100 Diseqc
Comag sl100hd
My Location
51.6 N, 1.2 W Didcot UK
The stickys on how to setup a dish or motorized system are good. But I think the old mod of adding washers between lnb arm and the bracket at the back of the dish to fine tune the lnb-dish focal point alignment should be added as a final step.

From a old thread
If you are using the Triax TD110 and do not have a long necked Lnb the dish gets an improvement of upto 15-35% by doing the following mod

Raise the lnb arm, by placing two penny washers between the rear of the arm and the slider braket. ie undo the butterfly bolt and push the arm up stick two washes in and do it up.

Push the arm in (c. 15-25mm depending on the lnb) and add packing to aim the lnb to middle of the dish (it will be lower) (you'll also have to tweak dish elevation afterwards too)


I have just tried out the mod adding washers between the lnb arm bracket and the dish but not altering the elevation/declination angles on my dish mount. With my Televes 1mtr dish. Doing the Triax TD110 mod, adding two washers to the top bolt between arm and back of the dish bracket significantly lowered signal quality.

But on my Televes 1mtr instead putting a single washer to the bottom bolt between the arm and the back of the dish bracket, then watching signal quality as I retighten the bolts showed an improvement. Signal quality on Badr 26E MBC Action went from 62% before any modifications to 68%. So that improvement proves Lnb - dish focus alignment is now improved on my dish.

It is a bit foggy here and I normally get around 64% signal quality on BADR 26E MBC Action, while picture brakes up at <45% signal quality so it is weather proof anyway. But I figure the slightly improved Lnb-Dish focal point could improve reliablity of weaker satellite channels like some of those from Nilesat 7W. It is about as big or bigger improvement than I have seen between different Lnbs, so if people buy better Lnbs in the hope of slightly improved performance, variations of this mod may be worth trying out.

Also I think it would be a good idea to mention dish assembly, warning people not to overtighten the backplate to the dish - deforming the dish surface, as this seems to be quite common.

Needing a vertical pole is rightly emphasized, but I would add not buckling the motor bracket when tightening it to the pole, checking the top of the motor casing the point it pivots on when setting its elevation is level, and checking the sides of the bracket are vertical. If the pole is not vertical or the motor mounting bracket is buckled you have to adjust the elevation angle.
For setting the elevation angle on a Moteck sg2100 using a inclinometer I think it would also be useful to mention the line where the two halfs of the motor casing join or the bottom of the motor casing between the f-connectors can be used as reference.

On a side note the instructions for installing the Moteck sg2100 could do with making it clear what markings you use when setting the latitude/elevation. There is an arrow marketing and a line. The sticky "from start to finish ss2/progdvb/motor/diseqc" pictures seem to indicate you use the line not the arrow. While the sticky "Pictorial Setup Guide for DiSEqC Motor - Downloadable PDF" pictures would seem to indicate you use the arrows. I do not know how much varation there is in the motors but on mine the arrows are a better indication.
 
D

dovercat

Member
Messages
28
My Satellite Setup
Televes 1mtr dish (102x113cm, Gain at 11GHz 40.5dB, Beamwidth 1.98degrees)
Televes 0.5dB LNB
(gain 57dB, discrimination 25dB, oscillator stability +/-2MHz, phase noise max-75dBc@10KHz)
Moteck 2100 Diseqc
Comag sl100hd
My Location
51.6 N, 1.2 W Didcot UK
The stickys on how to setup a dish or motorized system are good. But I think the old mod of adding washers between lnb arm and the bracket at the back of the dish to fine tune the lnb-dish focal point alignment should be added as a final step.

From a old thread
If you are using the Triax TD110 and do not have a long necked Lnb the dish gets an improvement of upto 15-35% by doing the following mod

Raise the lnb arm, by placing two penny washers between the rear of the arm and the slider braket. ie undo the butterfly bolt and push the arm up stick two washes in and do it up.

Push the arm in (c. 15-25mm depending on the lnb) and add packing to aim the lnb to middle of the dish (it will be lower) (you'll also have to tweak dish elevation afterwards too)


I have just tried out the mod adding washers between the lnb arm bracket and the dish but not altering the elevation/declination angles on my dish mount. With my Televes 1mtr dish. Doing the Triax TD110 mod, adding two washers to the top bolt between arm and back of the dish bracket significantly lowered signal quality.

But on my Televes 1mtr instead putting a single washer to the bottom bolt between the arm and the back of the dish bracket, then watching signal quality as I retighten the bolts showed an improvement. Signal quality on Badr 26E MBC Action went from 62% before any modifications to 68%. So that improvement proves Lnb - dish focus alignment is now improved on my dish.

It is a bit foggy here and I normally get around 64% signal quality on BADR 26E MBC Action, while picture brakes up at <45% signal quality so it is weather proof anyway. But I figure the slightly improved Lnb-Dish focal point could improve reliablity of weaker satellite channels like some of those from Nilesat 7W. It is about as big or bigger improvement than I have seen between different Lnbs, so if people buy better Lnbs in the hope of slightly improved performance, variations of this mod may be worth trying out.

Also I think it would be a good idea to mention dish assembly, warning people not to overtighten the backplate to the dish - deforming the dish surface, as this seems to be quite common.

Needing a vertical pole is rightly emphasized, but I would add not buckling the motor bracket when tightening it to the pole, checking the top of the motor casing the point it pivots on when setting its elevation is level, and checking the sides of the bracket are vertical. If the pole is not vertical or the motor mounting bracket is buckled you have to adjust the elevation angle.
For setting the elevation angle on a Moteck sg2100 using a inclinometer I think it would also be useful to mention the line where the two halfs of the motor casing join or the bottom of the motor casing between the f-connectors can be used as reference.

On a side note the instructions for installing the Moteck sg2100 could do with making it clear what markings you use when setting the latitude/elevation. There is an arrow marketing and a line. The sticky "from start to finish ss2/progdvb/motor/diseqc" pictures seem to indicate you use the line not the arrow. While the sticky "Pictorial Setup Guide for DiSEqC Motor - Downloadable PDF" pictures would seem to indicate you use the arrows. I do not know how much varation there is in the motors but on mine the arrows are a better indication.
 
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