Multi-LNB any good on Channel Master 180?

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Hello everyone,

Question: Is the CM/Andrew/Raven 180 cm dish suitable for a multi-LNB setup?
I want to keep the amount of dishes on the house / in the garden down, and I am therefore considering to use my CM 180 centered on 28.2E with a some form of suitable bracket+LNB to also pick up 19.2E (and poss others too).

It is tempting to think that having a large dish might make it easier to use more off-centre LNBs, since they would still get a substantial area of dish to received signal from. Maybe even 13E and 5E could be accommodated?

My concerns are these:

  • From reading posts here and elsewhere, it seems the larger the dish the more problematic alignment becomes, and thus LNBs not centered on dish seems to be in more trouble than with a smaller dish.
  • I have never seen a reference to a multi-LNB adapter/bracket suitable for the CM180, nor have I seen anyone having such a set-up.

Is this a case of "of-course-it-works-but-most-people-with-CM180s-at-28.2E-just-watch-Sky-and-nothing-else", or is this simply "too-much-trouble-when-fringe-receiving-just-buy-a-normal-dish-for-everything-non-28.2E"?

St1
 
You will probably find thet the support arms will be in the way of an offset LNB.
 
Hi Rolfw: I see what you mean.

Although it doesn't stop people from selling things like a dual-LNB holder (for the US market I believe). Just looks a bit - erh - strangely configured to me...

Nevertheless, with a suitable mod to the support arms (i.e. new homebrew U frame or similar), would is still be difficult to make work?

St1
 

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Let me just clarify that post:

With a suitable entirely new support arm design fitted would multi-LNB operation work on this dish?
If so, how to go about calculating where the offset focal point would be, so that a suitable positioning could be made?

St1
 
I guess it could, but if you need the central focus for 28.2, you may be foolish to muck around with the supports.
 
Firstly you need to work out roughly where the 19E LNB needs to go.

You can look up the elevation and azimuth angle differences between the two satellites, the 19e LNB will need to be offset by those differences, but mirrorred.

Then you can get an LNB, connect it to a receiver or meter, hold the LNB in your hand, and try and see if you can hold it in a place that picks up 19E well enough. The LNB should point at the centre of the dish still. If you find a place that works well, devise a means to fix it there.

I would't mess with the CM support arms either, get it wrong and you could muck up your 28e.
 
Somewhere in the forum is a technical diagram of the 1.8m complete with dimensions. I would peak the dish as usual on the centre satellite and simply hold the second LNB to one side with a squwarker meter, and count off the satellites until the right one is found. This will give you an idea of the lengths the two satellites are apart from each other and a boom arm can then be constructed out of copper piping, ala Vipersans design.
 
Thanks, guys.

Rolfw: I agree. I wasn't thinking of bringing out the hack-saw just yet :) Just saw this american design with a U-shaped bracket that entirely replace the feed-arms, and which has LNB holders going off it. Alas I am not sure this is practical for a CM180.

Robbo, Channel-hopper: Seems like a good plan. Since 19E is not really fringe reception here, it could bring some reasonable signal even if parts of the arms are in the way. Making a simple bracket should help do the job.

St1
 
st1 said:
Since 19E is not really fringe reception here, it could bring some reasonable signal even if parts of the arms are in the way. Making a simple bracket should help do the job.
Click to expand...

Or you could attempt a motor upgrade, which would bring out the best in your system.
 
Yes, I could, but that would probably be overkill. Motorizing to the degree of getting reliable 28.2E here will be expensive, particularly on a 180 cm Channel Master (I understand the mounts are not even made anymore).

The plan now is to point the dish at 28.2E, and try a side-feed for 19.2E. Although some american websites suggest that +/- 25 deg is possible on most standard (0.6 F/D) dishes, I doubt I can pull in 4.8E reliably on the CM. I will keep the small "standard issue" elliptical dish for that, and consider swapping that for an 80cm steel thing for 4.8E and 13E.

Again, finding room for a 60 cm dish is *peanuts* compared to finding a spot for your 180 cm dish in you garden with full WAF.

Heigh-ho.


St1
 
maybe something like this is what you need as that looks like a channel master 1.8 or 2.4m with some kind of offset bracket for multi lnb setup

_http://www.apexsat.com/accesories/0383899c1d09e9806/index.htm
 
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