Tests of 120cm antennas

[RimaNTSS]

Perhaps there is solution how to use original LNB holder on CM120. All is needed is to lift LNB in the holder (longer INOX screws are to be inserted) , and some kind of spacer under LNB (I put a pencil, but it is just to demonstrate). If LNB axis is leaning downwards 8,1* and it is lifted about 10mm, than it is possible to improve performance of the system.

 

[Trust]

About the same solution I made for the Laminas OFC 1200-P .
Thats why I wanted your old rusty CM lnb holder for the exact dimentions .

 

[RimaNTSS]

Thats why I wanted your old rusty CM lnb holder for the exact dimentions .

It is waiting for you...... in my garage

 

[Archived-1]

I just did this to do my tests, i put a small piece of wood on the back of the original holder with tie wraps, then screwed this to the wood at different heights, 5 minuets to make and setup.

 

[RimaNTSS]

Wim! When/if you going to make proper LNB holder from original one, there is drawing I made FYI.
Approximately 35mm from LNB's Phase center center of LNB holder is located. So, to lift LNB's Phase center and lean LNB 8,1* down you need to make center of LNB holder approximately 13mm higher. Than it should do the trick.

 

[RimaNTSS]

I just did this to do my tests, i put a small piece of wood on the back of the original holder with tie wraps, then screwed this to the wood at different heights, 5 minuets to make and setup.

..... pictures? I mean, more pictures?

 

[Archived-1]

Sorry its posted now .

I just did this to do my tests, i put a small piece of wood on the back of the original holder with tie wraps, then screwed this to the wood at different heights, 5 minuets to make and setup.

 

[Archived-1]

You could also do it this way, just bend the lugs to an L shape then put a hole through the lugs you've bent so the lnb screws fit through and fix it to the holder, you raise it via packers under the lugs, but only any good for fixed.

 

[RimaNTSS]

Martin! Do not really understand how are you going to attach this clamp to the dish. Do not forget to post picture when it is installed.

 

[Archived-1]

Ive already installed it done my test and thrown it away, it does not track the arc you would constantly have to adjust the dish.

 

[Archived-1]

Martin! Do not really understand how are you going to attach this clamp to the dish. Do not forget to post picture when it is installed.

There was a clue in my post Rimants

i put a small piece of wood on the back of the original holder with tie wraps, then screwed this to the wood at different heights,

 

[RimaNTSS]

Still do not get it! If you where losing arc maybe your LNB was moved sideways? Pictures would certainly help. Next time?

How small/big was piece of wood? What kind of wraps there? Then it was screwed to another piece of wood.

How much did you lift LNB and what was it's leaning angle?

 

[Trust]

Martin , me too don't understand why it should not follow the arc in that way . I'm convinced it should .
Saturday (or maybe sooner) I will test it . (not with a CM)

 

[Archived-1]

Sorry i will explain better ,It does track the arc but signal levels get lower the further E/W you go compared to signal levels monitored with original holder, so its not tracking as it does with the original holder in its correct place,

You can get more signal level with the lnb slightly raised on a fixed satellite but leave it there on a polar mount you lose the arc/signal levels drop further E/W you go.

 

[RimaNTSS]

You can get more signal level with the lnb slightly raised on a fixed satellite but leave it there on a polar mount you lose the arc/signal levels drop further E/W you go.

Are there any logical reasons to be like that? Could it happen that not only elevation but also declination should be adjusted to get the full arc? Did you record signal levels during your tests?

 

[Trust]

If you change the aiming point , man has also to correct the elevation of the dish .
Doing that with the motor elevation , will give that (better ?) signal at the sat youre pointing to at that moment . ( maybe you did it that way ?)
Turning to further east or west will give the problem not following the arc .
The elevation should bet corrected by the declination .

Edit , I see Rima is a bit younger than me .

 

[Archived-1]

I am totally aware of this and adjustments was made, do the tests yourself it the easiest way for you to understand . i am rubbish at explaining

 

[Archived-1]

Hi, after further tests with the CM 1.2, ive found the best place for the lnb is slightly lower than were the manufacturer puts it 4mm to be precise, by levelling the top of the PM instead of the pole and lowering the lnb arm, I have gained a good 15% signal on a transponder at 60E and gone from no lock to lock with picture, and ive gained signal all over the arc, this is the modification and it will now be able to except muti lnb .
https://www.satellites.co.uk/forums/threads/channel-master-dish-arm-modifications.164288/page-2

locking Kuban 11490 V 5788 now, weak but locked , please ignore my sat position.
https://www.satellites.co.uk/forums/threads/60e-intelsat-904.163004/#post-930434

 

[RimaNTSS]

Martin! When your antenna is pointed to the central satellite, what is it's leaning? I mean, is your central satellite has elevation for example 30* and offset angle of CM120 is 22,6*, than the leaning of the dish should be 30-22,6= 7,4*backwards. Could you check that? This will exactly show whether you've placed LNB in such a way that it's phase center is co-located with antenna's focal point.

 

[Archived-1]

Martin! When your antenna is pointed to the central satellite, what is it's leaning? I mean, is your central satellite has elevation for example 30* and offset angle of CM120 is 22,6*, than the leaning of the dish should be 30-22,6= 7,4*backwards. Could you check that? This will exactly show whether you've placed LNB in such a way that it's phase center is co-located with antenna's focal point.

Sorry Rimants I have nothing to check this with accurately, I get my dish as near as dam it with a rubbish inclinometer then fine tune to a signal, you might want to try this method instead off all this technical stuff,

This will exactly show whether you've placed LNB in such a way that it's phase center is co-located with antenna's focal point

I am quite sure it cant be far away or I wouldn't be getting the results I do .