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set up from scratch vbox and angles

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Ex Member
Ex Member

May 15th, 2011 at 12:02pm  
Folks be gentle to a newbe Smiley

I have a 2mt center focus dish mounted on a polar mount, actuator is 24in 36V, I have a V-Box and a DVB-S unit with DiSEqC 1.2.

I have the mount centered on true south. The mount is at a angle of 55.06 and the dish is at 7.02 dish is at Latitude: 54.4125°

a few questions please:

I have my DVB-s box connected to the V-Box and the V-Box connected to the actuator. I can move east-west.

What do I need to do in what order in that I can pick up the sats, I mean do i use the V-Box to move the dish and get the best signal strength and quality signal then store the sat in the V-Box and the DVB-s or do I use the DVB-s box only to drive the dish using DiSEqC and store on the DVB-s box?

The LNB what should it be set at?

There is a adjustable feedhorn on the C120 LNB what /where is the starting distance for it? How in what order do I adjust it to max the signal? e.g do I set the dish pointing at a known sat, take the signal strength reading and the quality reading and then (what) move the feedhorn in and out to max the S/N reading? or rotate the lnb for max?

Simple instruction in a logical order is what I am after please.

Thanks IA.
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Eric Johnston
Senior Member

Posts: 2109
Reply #1 - May 15th, 2011 at 4:07pm  
With the dish drive motor centralised and the dish aimed due south, set the LNB polarisation to vertical/horizontal.  It needs no adjustment.   The polarisation will automatically rotate clockwise for satellites to the south west and anticlockwise for satellite to the south east, as the main polar actuator moves.

With the exact angles you have set your dish will see all the satellites in turn as the motor moves it across the sky.   If the angles are not exact (including the due south alignment) there will be errors and these will mean that:
You see no satellites at all.
You see only some satellites towards the south east.
You see only some satellites towards the south west.
You see only some satellites towards the south.

A simple in-line noise power meter will help you peak up and determine which way is each satellite.  Your receiver will supply +13/+19V DC power and 22kHz tone OFF/ON.

Imagine the satellites in a curved line across the sky. Your dish also sweeps out a curved line. The two curved lines should be superimposed, but in practice, with errors, the lines will be parallel above or below one another, cross over once or twice. meet at one end and diverge at the other etc.  If any of these errors you will not see some or all satellites.

I think the general feeling is that you should try to find the nearest due south satellite first.
Then move off either way and once problems are detected then gently push on the dish to try and identify the error direction and then make small adjustments to the mount and dish angles.

Be warned, with a 2m dish you may spend several weeks trying to do the set up and may still not succeed.

The quickest results are obtained by setting the main polar axis angle very accurately (0.1 deg accuracy) as this is the only angle that can be set accurately by local mechnical measurement. Use an accurate inclinometer or plumb bob thread. Then find the nearest south satellite. Do the following: Offset the dish dip to peak up. Set the motor sideways angle few deg as per calculation ( Peak up using the clamp on the mount pole to get due south correct.  Repeat through this process until successful.

Read the instructions with your dish, the motor controller and your satellite TV receiver.

Good luck.

Best regards, Eric.
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« Last Edit: May 15th, 2011 at 5:49pm by Admin1 »  
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