C band LNB re-attached to my Channel Master 1.8

scopus

scopus

Specialist Contributor
My Satellite Setup
Primesat/Famaval 1.8 PF C/ku/Ka, Octagon SX8HD1, SX88, Openbox S3 Mini HD-V8S Freesat V7 HD-V8 Finder, Amiko A4K Combo, Satlook Colour HD Spectrum, Sansui A909 Amp and BOSE Acoustimass speakers for the audio.
My Location
Staffs UK
After much experimenation with Ka band I have re attached my C Band back on top of my Ku LNB with a coach bolt and a perfect fit bracket from the local Tyre and Battery fitters. Good signals from 10E,20E,27W,22W,5W,3E,26E and 18W on the F15 which is now my dedicated C Band receiver.
 

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Neat setup. How have you modified your support arms to allow for the extra LNB on the side? I've been thinking of doing something similar for my CM 1.2m.
 
timo_w2s said:
Neat setup. How have you modified your support arms to allow for the extra LNB on the side? I've been thinking of doing something similar for my CM 1.2m.
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Yes, I did that when I was experimenting with the Ka. I might do the same to the other side in the spring, when the weather gets better, and get the C band on the other side of the Ku.
 
timo_w2s said:
How have you modified your support arms to allow for the extra LNB on the side? I've been thinking of doing something similar for my CM 1.2m.
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This mod is more complicated on the 1.2m because of the way the side arms are attached to the dish (in the hole on the 1.2m rather than on the sides on the 1.8m, which allows you to move the arms down).
 
Captain Jack said:
This mod is more complicated on the 1.2m because of the way the side arms are attached to the dish (in the hole on the 1.2m rather than on the sides on the 1.8m, which allows you to move the arms down).
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I see, damn. OK thanks. It's something to work on next summer I think.
 
You would only have to spin it out of the way the bend on it will naturally do that for you with the 1.2 same difference really as the 1.8, if your only doing one side.
 
What I don't understand is why no one has done rx/tx dish arms mod, it looks so easy to do, its what I will be doing:).
 
Skyware does do these mods.. Here's one with a Fibo-type sub-reflector.
type_184.jpg


You're right, though, Martin - not difficult to do these yourself. Thinking about the 1.2m one, you could probably do what you're saying too.
 
timo_w2s said:
Neat setup. How have you modified your support arms to allow for the extra LNB on the side? I've been thinking of doing something similar for my CM 1.2m.
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As CJ has said they are only bolted to the side on the 1.8 so the drop easily, but they actually go through the dishface on the 1.2. Spinning them might be an option like Martin-f has suggested.
 
Feedarms for those dishes were designed first only for one LNB, and secondly- for 20 or 23mm diameter of the feedhorn or LNB's neck. So if you just place 40mm LNB in original holder that means that LNB automatically will be out of focus and system will not be abble to perform at it's possible maximum.
I think, that it is not so difficult to make completely new feedarms, so antenna will be OK for multifeeds and central LNB will also be placed in the focus.
There my old feedarm on Prodelin 1,8m before and after. Before I could not adjust position of LNB, but now I can.
Before.webp After.webp feedarms.webp
If somebody needs my old feedarms can have them free of charge, only post costs.
 
RimaNTSS said:
that means that LNB automatically will be out of focus and system will not be abble to perform at it's possible maximum.
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I will just make a 4 point laser jig to pin point the LNB before I start the mod, doing it like that i cant get it wrong and the LNB will be sat were it should be after the mod :).
 
martin-f said:
I will just make a laser jig to pin point the LNB before I start the mod, doing it like that i cant get it wrong and the LNB will be sat were it should be after the mod :).
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That is right, but can be not enough. If yo move LNB any direction, lets say 20mm, than you will still be able to point LNB to same spot on surface of your antenna. Pointing LNB to right spot ("Le point G") it is important, bet position of LNB in space when LNB's phase center located exactly in focal point of antenna is also very important. One more thing, which is important- LNB's illumination angle is same to antenna's opening angle.
:)
 
The G spot changes with different types of setup/LNB type, so you will never get this spot on only on a fixed dish using one LNB,
 
Sorry Martin, did not get you.... G spot for central LNB newer change it's position, that is concrete point on the surface of the dish.
 
It does not mean you will get the best signal pointing to this spot, that's why some lnb types move electronically to hit another spot to pull the signals in better,

I am not going to get into a debate on this and I will leave it at that :).
 
Captain Jack said:
I wonder how much they cost from Skyware (not good with modding stuff myself)
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mods should we open a new thread for discussing how to mod the dish for new arms? rather than cluttering Scopus's thread on his CM1.8 with off topic discussion? Not to single out CJ or anyone else. or has one already been opened? I have some input on the modding topic I can share.
 
martin-f said:
It does not mean you will get the best signal pointing to this spot, that's why some lnb types move electronically to hit another spot to pull the signals in better,

I am not going to get into a debate on this and I will leave it at that :).
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I have always found the theory is not always what you get in practice:);)
 
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