New feedarms for an offset dish

[RimaNTSS]

I would like to start this thread for those who are looking for feedarms for their offset dishes. Original feedarms can be broken, lost and even never made for particular dish. I've designed feedarms for several offset dished , and I think that I got them right. So here I would like to go step-by-step procedure for calculating proper feedarms. As an example we can take any dish. I offer to take Channel Master 1,2m, the dish with well known dimensions and parameters. But, if somebody, for example @st1 , wish to use another dish like 2,4m Prodelin, we could use it as well. But then we would need exact measurements of that dish.
So, Channel Master 1,2m?! 1200x 1300mm dish with 22,6*offset angle ?

 

[archive10]

So, Channel Master 1,2m?! 1200x 1300mm dish with 22,6*offset angle ?

Very well, I have several sets of CM120 arms, so those are well covered.

I do however (leaving the Prodelin 1241 aside for a moment) have a Laminas OFC 1200 dish without feed-arms.
Now I could order a new batch from Laminas (I hear they are willing to supply spares), but that would be perhaps too easy.
Instead, I would like feed-arms that would not obstruct the reflector, and would support multiple LNBs (even multi-band LNBs - Ka center, Nu offset, C more offset).
How should I measure the dish?
What dimensions do you need?

You should probably also aim not at supplying said dish arms, but rather providing step-by-step instructions (simplest and easiest) on how to make the feed-arms. This would allow people all over the world to make the feed-arms, and save you a lot of trips to the DHL drop-off point!

 

[RimaNTSS]

Instead, I would like feed-arms that would not obstruct the reflector, and would support multiple LNBs (even multi-band LNBs - Ka center, Ku offset, C more offset).

Almost any feedarms (especially side-feedarms) will obstruct the reflector, unless you wish them very wide. I think it is not necessary... let them obstruct some surface of the dish, that will not be great area we are speaking about. Multiply LNBs is fair point, and, I think it is pretty doable, but do not look at miracles like receiving from satellites at 30 or more degrees separation.

How should I measure the dish? What dimensions do you need?

Measurements should be done with the precision of ~1mm vertical and horizontal size. Depth preferable with the precision of 0,1mm.

don't even have to go to the Russian focal-point calculator

I am afraid we will be forced to go to some program to calculate precise location of antenna's focal point.
My aim is t0 allow people to make feedarms themselves without me going to DHL drop-off-point.
I think we can look at extendable side feedarms, so there will not be any major difference between 1,2m CM and 1,2m Laminas dishes. To not spoil the dish we can look for feedarms which can be attached to the dish without spoiling anything, I mean it will be always possible to roll-back to the original feedarms.
For a purpuse of this discussion we can take as a sample dish your 1,2m Laminas. Then, please measure it very carefully (only the working area) , as we will go to some precision drawing afterwards. Horizontal size- ?mm, Vertical size - ?mm, Depth - ?mm

 

[Channel Hopper]

I have the technical drawings for a number of larger antennas stored on the old office pc.

A lot of them are also dotted on different parts of this site, so most of the time, an intelligent search may bring up a positive result.

 

[Captain Jack]

I would like to recreate the feedarms for the 1.8m Channel Master that doesn't require the dish to support it; i.e. hanging entirely from the back bracket.

Over time, the weight of the LNBs can and does deform even the most rigid dish structures, let alone the flimsies like the Gibertinis...

 

[Channel Hopper]

I would like to recreate the feedarms for the 1.8m Channel Master that doesn't require the dish to support it; i.e. hanging entirely from the back bracket.

Over time, the weight of the LNBs can and does deform even the most rigid dish structures, let alone the flimsies like the Gibertinis...

The r/t version of the CM180 has a completely different mounting point on the post, and this design is not suitable for motorising (easily). I will look for the diagrams

 

[RimaNTSS]

I would like to recreate the feedarms for the 1.8m Channel Master that doesn't require the dish to support it; i.e. hanging entirely from the back bracket.

It is not so easy to make. In fact once we (Wim and I) tried to make something for CM 1,2m First of all, it is lots of additional weight will be added. Secondly, there is clear need for sidearms. And, finally, IMHO the gain after all this pain will not be so great.
Of course, some antenna-producers made several antennas with feedarms connected directly to the mount, for example Kathrein but that is mostly for smaller dishes. SMW dishes OA-1400 "Jumbo" and OA-1600 also have all feedarms connected to the mount.
For Channel Master 1,8m it is much easier to make additional pulling struts at the back of the dish for dish shape correction.

 

[Anonymous_1]

I have this RX/TX LNB holder for the CM 2.40m :



And I want to replace it by a more regular LNB holder (feedarms are probably the same )

I wish something where I can easily change LNB from C KU, KA, X , for now, I am working with a LNB holder made by Rima for KU and myself for Cband (using LNB changer inox parts)
I use this antenna for testing various LNBs and positions

the CM LNB holder is like this:



(This antenna will be motorised during 2017 and I need something lighter than the TX/RX LNB holder)
for the motorization, I will ask separately, 2 options: bigpolar made by an Italian guy, built in stainless steel or the Primesat CH24100.

 

[Channel Hopper]

I have this RX/TX LNB holder for the CM 2.40m :

View attachment 101685

And I want to replace it by a more regular LNB holder (feedarms are probably the same )

I wish something where I can easily change LNB from C KU, KA, X , for now, I am working with a LNB holder made by Rima for KU and myself for Cband (using LNB changer inox parts)
I use this antenna for testing various LNBs and positions

the CM LNB holder is like this:

View attachment 101686

(This antenna will be motorised during 2017 and I need something lighter than the TX/RX LNB holder)
for the motorization, I will ask separately, 2 options: bigpolar made by an Italian guy, built in stainless steel or the Primesat CH24100.

Whilst the downgrade to receive only is rather simple (the reflectors are the same and the bolt holes for the feedarms are on the fibreglass parts only) the supports will still require strengthening on anything above a twin LNB system.

Have you considered the 'Vickers' system I proposed a few months back for LNB swops ?

 

[Anonymous_1]

Have you considered the 'Vickers' system I proposed a few months back for LNB swops ?

Can you refresh my mind, I think I missed this one...

 

[Channel Hopper]

New Lnb changer

 

[blademedia]

This is the best design ive ever seen for channel master, i will be making this for my project with my own modifactions