New Dish needed for 28E: Selection and Installation

[a33]

Hi. According to Dishpointer on my PC, I need a skew of 10.2 whereas the app on my phone says 17.7. The difference is 7.5 which google tells me is the pre-skew on the Astra satellites. But what google hasn't so far told me is which one do I go with when installing my LNB - Dishpointer or the phone app? My thanks if you can help me out.

In this case, you follow dishpointer.
The easy test: enter 28E as your longitude, in the calculator. If the skew-value is then zero, no pre-skew is accounted for.
In this case the skew from dishpointer says skew=7,3 (I used 28E instead of 28.2E), so the pre-skew is included.

Don't think dishpointer is right always, though!
All the eutelsat satellites (such as 13E) seem to have a pre-skew of 3.535 degrees, according to some rather official looking documents, but I don't think many skew calculators take that into account.

The satlex calculator indicates the included and excluded preskew skew value for the astra satellites (as "special case"), so that you can see what value to use...

Greetz,
A33

 

[pooksahib]

Great stuff - thanks, A33.

 

[pooksahib]

Hi. My Triax dish came today and has only one pole clamp (2.75 inches wide with three straight sides i.e. NOT U shaped). I think I'd prefer 2 of these clamps for peace of mind. So far, I'm only seeing U and V shaped bolts for sale. Would that be a problem?
Or are the good folks here quite happy with one clamp?

 

[ozumo]

Should be ok, what size pole are you using?

 

[pooksahib]

Here's a pic of the pole. I have another issue now in that the Triax's LNB collar clips together nicely on its own but put it around a 40mm LNB and - well, see the other pic. Has anyone had this problem before and, if so, how do you get round it? I could force it together with the screw but surely that shouldn't be necessary...

 

[ozumo]

Is it a Sky LNB?

 

[Lazarus]

Is it a Sky LNB?

Small file on stand-by ..........

 

[jeallen01]

3x Triax dishes here but never had that problem - the upper "lock together" ends of Triax LNB clamps break very easily, especially in cold weather!

If in any doubt then put a long cable tie around the whole clamp to try to prevent it happening, or at least to "compensate" for the breakage. OTOH, replacements are easily available on ebay (but they are no better than the originals).

PS: is the LNB clamp/holder in the photo an original or a "replacement" (the originals are, AFAIK, made of Black plastic - so I think that one is a "replacement"!)?

 

[pooksahib]

It's an Inverto LNB, not a Sky. The dish is grey so it makes sense for the plastic bits to be grey also. All parts out of the box so should be original.

 

[jeallen01]

PS to Post #26 - might be an idea to put a very small spacer of some sort in the gap, such that the clamp prevents the LNB being rotated when the bolt is tightened, but doesn't overstress the clamp itself.

 

[ozumo]

PS: is the LNB clamp/holder in the photo an original or a "replacement" (the originals are, AFAIK, made of Black plastic - so I think that one is a "replacement"!)?

I believe the dish is a fibre glass Triax DAP, promo photos all show they have grey LNB holders

 

[pooksahib]

Thanks for all the input so far. Next question - any idea what an Nm is?

 

[ozumo]

Nm = Newton metre is a measurement of torque. Just means use a spanner or wrench and not fingers when assembling.

 

[jeallen01]

I believe the dish is a fibre glass Triax DAP, promo photos all show they have grey LNB holders

Thx because I wasn't aware of that - OTOH, I think my comments about "protecting" the LNB clamp/holder would still apply.

 

[jeallen01]

Nm = Newton metre is a measurement of torque. Just means use a spanner or wrench and not fingers when assembling.

Unless you have an arm + spanner combo that is "calibrated" in Nm, then a Nm number in the spec would imply use of a calibrated torque wrench - OTOH, a bit of basic mechanical engineering experience and "common sense" should tell anyone when a nut is "tight enough", and should not be tightened any further.

FWIW, it took quite a few years for my brain to learn that lesson, but the actual indication of "when to stop" tightening a nut is when the effort required to do that "suddenly" increases significantly - tighten it much further and then "something" will almost certainly "break"!

 

[pooksahib]

I believe the dish is a fibre glass Triax DAP...

Actually, a Triax TDA64 aluminium. The LNB collar has some small inner ridges, I might try sanding them down to get a better mating of the two halves. The LNB clamp breaks 'very easily' says jeallen01. Gawd, the things you wish you'd known before you bought... Enough for one night, I'm off to bed. Thanks again, guys.

 

[jeallen01]

"Mating the two halves" is not really that important - the main target is to ensure that the LNB is prevented from unintentionally being rotated. OTOH, if the halves of the clamp are not "mated" when that happens, then, as I said earlier, put some sort of spacer between them to ensure the clamping nut is "tight" but the halves are not "over-stressed".

 

[pooksahib]

Hi, jeallen01. Unless we're at cross-purposes, surely the mating of the two halves is very important - the bottom needs to come together to form the rectangle which clips into the arm, no?

I see on the Triax website that they do an aluminium LNB bracket:

Products

www.triax.com

But this looks to be a 'trade-only' site. Does anyone know of a good outlet for Joe Bloggs to get Triax accessories?

 

[jeallen01]

Hi, jeallen01. Unless we're at cross-purposes, surely the mating of the two halves is very important - the bottom needs to come together to form the rectangle which clips into the arm, no?

Sorry - had forgotten that "important aspect", but, TBH, I am still not totally convinced that that is a genuine Triax clamp. Nevertheless, it looks as if you may need to mod it by removing some of those ribs.

OTOH, I have 3x Triax dishes with Black LNB holders/clamps from various sources, and of various ages (but none less than about 5-6 yrs old), and - even with cheap, possbly "clone", replacement LNB holder/clamp kits from ebay - I've never encountered that problem because they all have a bolt + nut through the "neck", between the LNB and the bottom end. You had just had to do that up moderately tightly to pull the two halves of the clamp together before pushing it into the end of the dish arm (that can be a little awkward because of the little "lugs" on either side which eventually pop out of square holes in the arm).

Your posted images don't show the sides of the clamp - so does it have recessed holes on both sides through which you can fit a bolt + nut like that?

PS: From a quick look at the Triax site, it looks like the older ranges of dishes use the same sort of Black clamps as mine, whereas some of the newer ones have the grey clamps that fit on the outside of the arms, rather than being pushed into the ends thereof.

 

[ozumo]

Search for Triax 300721 on amazon. Not cheap though.