# More than one lNB on a dish

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#### patmos

##### SatelliteGuys Family
I am completing a 3.1m fibre dish. I intend to use it on IS 10 at 68.5 deg E on C band ( may be KU in future). How can I add a second LNB(C band) to get THAICOM 2/5 at 78.5 deg E. Where should I place the second one Right or left? when I'm in front of my dish. Remember I am in southern hemisphere and looking North. My coordinates are 20 deg 13 min S/ 57 deg 28 min E. Is there a formula or rule to follow. Any pics will be an aid to me.

#### Keith Brannen

##### SatelliteGuys Pro
I am completing a 3.1m fibre dish. I intend to use it on IS 10 at 68.5 deg E on C band ( may be KU in future). How can I add a second LNB(C band) to get THAICOM 2/5 at 78.5 deg E. Where should I place the second one Right or left? when I'm in front of my dish. Remember I am in southern hemisphere and looking North. My coordinates are 20 deg 13 min S/ 57 deg 28 min E. Is there a formula or rule to follow. Any pics will be an aid to me.

Simple rule, everything is backwards when adding a second LNB. For example, if standing in front of the dish (looking at the dish) and you would have to move the dish to the right to point at the satellite, then the LNB goes on the left hand side of the centre LNB. As well, if the satellite is higher in your arc than the centre LNB, then it goes lower than the centre LNB.

#### patmos

##### SatelliteGuys Family
Simple rule, everything is backwards when adding a second LNB. For example, if standing in front of the dish (looking at the dish) and you would have to move the dish to the right to point at the satellite, then the LNB goes on the left hand side of the center LNB. As well, if the satellite is higher in your arc than the center LNB, then it goes lower than the center LNB.
Thank you . But how to calculate the distance between the two?
Thaicom is lower ( 56 deg el) than IS 10 (63 deg El) So Thaicom LNB has to be HIGHER now by 7 deg but on the right instead of the left. Is there any explanation to this reverse arangement?

#### Anole

##### SatelliteGuys Master
... But how to calculate the distance between the two?
Read up on MJflash and his math to put two LNBs on a single dish:
http://www.satelliteguys.us/free-air-fta-discussion/89049-offset-lnbs-theory-practice.html
If you would like to read some threads where this math was put to use, I know Linuxman wrote two threads where he put two LNBs on each of two dishes.
I'm pretty sure there was discussion in one or both threads that'd give you good examples...

Thaicom is lower ( 56 deg el) than IS 10 (63 deg El) So Thaicom LNB has to be HIGHER now by 7 deg but on the right instead of the left.
Is there any explanation to this reverse arangement?
Well, think of the dish as a mirror.
So, all signals reflected by it are swapped left for right and top for bottom.

#### patmos

##### SatelliteGuys Family
thank you Anole I\ll go thru it. Have you done it in practice?

#### schlever

##### SatelliteGuys Pro
thank you Anole I\ll go thru it. Have you done it in practice?

I have done it in practice with the formula. It gets you to the right place, but it takes a lot of fine tuning .... keep at it .... it works!

#### SatelliteAV

##### SatelliteGuys Master
I hand hold the LNBF while looking at a meter, spectrum analyzer, or TV with the receiver's signal meter displayed. Usually can find the focal point in less than a minute, but then it takes a few minutes to place the bracket and tighten into position.

See photo below of the Satellite AV shop 1.8M offset dish with 4 degree separation for AMC4 Ku and Galaxy 25 Ku.

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#### patmos

##### SatelliteGuys Family
I'm confused about two calculations from MJflash

Horizontal offset = focal_length * sin(dish_azimuth - new_azimuth)
Vertical offset = focal_length * sin(dish_elevation - new_elevation)

Horizontal offset: focal_length * sin(new_orbital_position - old_orbital_position)
Vertical offset: horizontal_offset * tan(my_skew_angle)

Are the two vertical calculations similar? what is tan of my skew?

#### scottc98

##### SatelliteGuys Pro
See photo below of the Satellite AV shop 1.8M offset dish with 4 degree separation for AMC4 Ku and Galaxy 25 Ku.

Whoa....you sell a 1.8m offset? Or is that the 1.2m

#### SatelliteAV

##### SatelliteGuys Master
Have a few samples on the GEOSATpro 1.8M, but we decided not to sell as the demand is small and the shipping cost would be so high with custom crating and ground transportation.

We can arrange to drop ship the dish from another source if you are interested.

#### patmos

##### SatelliteGuys Family
what is the cost of such a dish? I tried to get one but to no avail.

#### Tron

##### SatelliteGuys Master
Interesting... looks like that dish is manufactured by Patriot. I'm sure the shipping would be quite high, it would have to be shipped via freight.

#### SatelliteAV

##### SatelliteGuys Master
\$485 with crating charge. Delivery costs would be heavy weight quote by common freight carrier. Delivery to a business address with loading dock will save big \$\$\$.

The dish is manufactured by our dish manufacturing partner, Azure Shine.

[FONT=Verdana, Arial, Helvetica, sans-serif]Specifications : 180cm / 6 feet[/FONT]​

[FONT=Arial, Helvetica, sans-serif]Offset Angle [/FONT][FONT=Arial, Helvetica, sans-serif]23°[/FONT] [FONT=Arial, Helvetica, sans-serif]
Aperture Efficiency
[/FONT][FONT=Arial, Helvetica, sans-serif]>80% [/FONT] [FONT=Arial, Helvetica, sans-serif]
Horizontal Axis
[/FONT][FONT=Arial, Helvetica, sans-serif]180 cm [/FONT] [FONT=Arial, Helvetica, sans-serif]
Vertical Axis
[/FONT][FONT=Arial, Helvetica, sans-serif]195 cm [/FONT] [FONT=Arial, Helvetica, sans-serif]
GAIN@12.5 GHz Ku-Band
[/FONT][FONT=Arial, Helvetica, sans-serif]47 dB
[/FONT] [FONT=Arial, Helvetica, sans-serif]Focal Length [/FONT][FONT=Arial, Helvetica, sans-serif]108 cm [/FONT] [FONT=Arial, Helvetica, sans-serif]
F/D Ratio
[/FONT][FONT=Arial, Helvetica, sans-serif]0.6[/FONT] [FONT=Arial, Helvetica, sans-serif]
Mount Type
[/FONT][FONT=Arial, Helvetica, sans-serif]Az/El [/FONT] [FONT=Arial, Helvetica, sans-serif]
Azimuth Alignment
[/FONT][FONT=Arial, Helvetica, sans-serif]360° [/FONT] [FONT=Arial, Helvetica, sans-serif]
Elevation Alignment
[/FONT][FONT=Arial, Helvetica, sans-serif]0[/FONT][FONT=Arial, Helvetica, sans-serif]° ~90° [/FONT] [FONT=Arial, Helvetica, sans-serif]
Pole Diameter
[/FONT][FONT=Arial, Helvetica, sans-serif]89 mm [/FONT] [FONT=Arial, Helvetica, sans-serif]
Operating Temperature
[/FONT][FONT=Arial, Helvetica, sans-serif]-40°C ~ +60°C [/FONT] [FONT=Arial, Helvetica, sans-serif]
Operation Wind
[/FONT][FONT=Arial, Helvetica, sans-serif]90 km/H [/FONT] [FONT=Arial, Helvetica, sans-serif]
Survival Wind
[/FONT][FONT=Arial, Helvetica, sans-serif]180 km/H [/FONT]

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