Seeking advice on Astra 2D optimising

st1

Hi,

I'm problems getting proper Astra 2D reception here just north of Copenhagen in Denmark.

IRDs: Pace Sky+ box (5 yrs old), and a Thomson Sky+ HD box (just under 2 years old).
Cards: Sky biewing cards for both boxes, converted to "Freeview from Sky" earlier this year.
Dish: Fortec 185 cm prime focus dish and an Invacom Universal Single LNB, both new from Maplin.
Cable: Tried both a 2 meter CT100 cable and a 30 meter RG-6 run with minimal difference. Only one run, though, connected to input one on the IRD.

There is a clear line of sight to where the satellites are. I can almost align the dish now by hand - I know the direction by heart. Azimuth requires a sat meter. 8)

I can get Astra 2A, 2B and Eurobird 1 channels (like BBC News, Sky News, FIVE, Ch4 HD, ITV Meridian SE + all the ehtnic channels) with no problem. With no clouds, I can get blocky BBC HD, and chirpy/blocky BBC Yorkshire. Very bad BBC1/2 and no ITV1/2/3 etc.

Using a TV explorer II+ signal meter, I get at most 61.5 - 63.2 dbµV signal strength on 28E2 "channel" 45 (Astra 2D 10773 MHz H 22000 5/6) with around 5.5 db C/N ratio. The TV instrument does say "carrier restored" as in contrast to signal lost, and may occasionally flash "MPEG2 TS", but not long enough to lock on and decode.

With 2A/2B transponders (and not fiddling with dish), I get 78-82 dbµV from the LNB, and something like 10-12 db C/N ratios. The TV explorer reads the TSs, and will decode and show the F2A content.

Dish is standing on it's ground mount (no mast mount available). I have tried relocating the dish sideways at four different locations with 2m intervals with no change. I have tried putting the dish higher (on a 60 cm table), with little difference. I have fiddled with the LNB focus (moving back anbd forth). I have fiddled with the Skew around the clock, but settled at about 3-5 degrees clockwise looking from the dish at the LNB.

At one point a couple of days ago, through shere luck, I got the output strength up to 65-67 dbµV. and could get BBC1 Yorkshire (I think it was) and BBC HD with no blocking or anything. BBC2 was chirpy and blocky though. I had to move the dish to release the table it was standing on to other uses, and have not been able recapture that performance again even though using same table.

I wuold be expecting to gain another 3-5 db to get all channels (esp BBC2 is sorely wished for), but I am now at a loss on how to achieve that. I am not expecting miracles, but I am know looking for any advice on optimisations such as:

- The dish is specc'ed to have 684mm focus point. But where on the invacom should the focus point be? At the tip? Somewhere in the middle?
- The dish is use-supplied-ground-mount-only. Does the height off the ground matter, i.e. should I build a slight platform to stand it on?
- is the Fortec cr*p and should be replaced with a solid (and more expensive) dish to get anything?
- Should I try a different prime focus LNB?

Cheers

kitschcamp

Basically, in my honest opinion, yes. The FortecStar is a steaming pile of whatnot.

I live just across the water in Skåne, and when I moved here I bought a 2.4m FortecStar. Biggest mistake I ever made. The 2.4m dish only just worked after spending a fortune on installers, different LNBs, different mounts, different feed horns, etc. By only just, I mean a slight rainstorm killed BBC etc...

Then one strong wind came six months later, and buckled it so it was useless. A huge huge waste of money.

The 1.8m ASC/Andrews/Channel Master dish, however, is a different story. Despite being .6m smaller than the 2.4m Fortec Star, it's in a completely different league and works fantastically even in bad weather. Aligning it and setting up is a piece of cake compared to the Fortec Star, also.

Don't waste your money trying to improve the Fortec Star, it's never going to be great. Save up, and get something decent.

I made that mistake, and I don't want anyone else to make the same mistake.

st1

Hi kitschcamp.

Yes, I did read your story on your installation elsewhere on this site with great interest. (And nice pictures too!)

I'm in a rented house at the mo, so I didn't want to do anything too drastic investmentwise. But I suppose that the old adage you get what you pay for applies here too. Was just hoping that the diameter (185 compared to 130-150 as indicated by many) would compensate.

I am still open to any and all tweaking suggestions (patience account not entirely empty yet), but I take you point.

Thanks

Topper

If you are renting, ask the landlord if he needs a duck pond fitting in the garden, from all the reports I have read over the years about it, that is about all it is really useful for, and you could at least recoup some money on the poor investment and get a few environmental brownie points as well

War does not determine who is right, it determines who is left!

Formerly toppervte33h
whose six pack has turned into a keg

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kitschcamp

No good even for that. The paint is really thin, and it rusts in no time, otherwise we'd have used it for our hen houses and goat shelters.

kitschcamp

Other than the Invacom Quad LNB with Invacom Feedhorn, nothing else makes much difference. There is virtually no way to accurately align it as the mounts and bracketry are so appalling.

Huevos

That dish could easily be out performed by a 50€ offset 1.2 metre dish. Also that dish comes with an LNBF which is not matched to the dish (post a photo of the LNB to confirm this or post the model number).

kitschcamp

The 2.4m dish comes with the wrong type of LNB, also. Which tells you a lot about the professionalism of Fortec Star. It doesn't even have the right LNB *holder* for a C120.

st1

The dish didn't come with an LNBF. I purchased the Invacom separately from Maplin. Incidentally this was the only LNBF they had for prime focus dishes - so not much choice there. The model number I believe is SNH-031.

Robbo

The technical department at Maplin are aware that the LNBF that they sell is not designed for Prime focus dishes, but they continue selling them as such. paying customers are obviously not deemed worthwhile, as this is the reply I received from them back in jan 09

and an extract from a previous email


Very Costly and seldom made-

The SNF-031 is the C120 version, but a feedhorn is also needed,

there is also the quad version QDF-031.


Not sure of the exact F/D ratio of that dish, but the Invacom adjustable feedhorn may do the job, with a 40mm to C120 reducing adapter.

st1

Hi Robbo,

sorry was just away on business for a few days.

So, what you're saying is that the SNH-031 is not a prime focus LNB?
In that case, is it then just picking up a smaller portion of the dish, or is it an offset type?

I think Maplin is then really on the edge of misleading customers here - the LNB is marketed as a prime focus LNB. If it isn't it shouldn't be positioned as one.

Question: If I can almost get Astra 2D with the SNH-031, it seems an SNF-031 with feedhorn might do the trick before moving onto more expensive dishes.

It also seems I need to understand what a C120 means - any pointers? (tried googling it but only found out where to buy them, not what they are...)

St1

st1

Update and Feedhorn adjustment question:

Just as you gentlemen say, the LNB Maplin sold me matches the dish only in the size of the clamp (40mm), not in F/D. The Invacom Universal SNH-031 has a fixed F/D of about 0.55, whereas the Fortec has an F/D of about 0.38. No wonder I can't get any decent reception despite the size of the dish.

Re the dish - it is not suitable for Scanwegian weather - it is (as kitschcamp points out) rusting like there is no tomorrow. But I am only renting for about 6 monhts more, so it is a temporary solution in any case.

The LNB is being returned to Maplin, I've purchased a C120 flange Twin Invacom TWF-031 instead, with Invacom ADF-120 Feedhorn from Satbuyer.co.uk.

Amazingly, the feedhorn comes with no installation instructions at all, and no markings on it at all to guide the correct setting of F/D to match my dish.

Question 1: Can anyone suggest how I figure out where the "baffles" part of the feedhorn should be positioned for a F/D of about 0.38?

Question 2: I know the focus point ought to be about 684 mm out from the base of the dish. Where on the Feedhorn should this be? at the tip?

thanks,

St1

Huevos

Mate you can't do this with maths. You just connect up a decent meter which at least shows C/N ratio and quality and just move the feedhorn in and out, and alter the skew until you find the sweet spot. Even with the same brand dishes the LNB depth varies from one install to another.

st1

Ok, I'm prepared for some fiddling to get the sweetspot of the set-up.

I would assume the Feedhorn would have a position of the baffle designed into it. Other mfgs seem to have F/D guidelines stamped to the side of the feedhorn...

However, I will give it a try tonight and see what happens.

Cheers

Huevos

If you have an adjustable feedhorn follow the manufacturer's instructions. To get the f/d correct you just screw the scalar ring part until the correct amount is protruding according to table that comes with it. Once that is set correctly you move the whole lot (LNB and feedhorn) in and out (towards and away from the dish) until you get the best signal quality.

st1

Ah! Nothing like that came with the adjustable feedhorn. Just the base part and the scalar ring in a cardboard box. I probably need to talk to have a word with Invacom on that.

But thanks for the instructions. (Actually just what I was looking for - I spent some hours searching here yesterday and found very little on the topic.)