Visiosat bisat - loss of signal during bad weather

[Bamboccio]

My 75cm Visiosat bisat points @ 13 and 19.2. Large clouds are enough to cause glitches on some the Astra HD channels. Could it be the 8 years old Fracarro LNBs or a loss of alignment?

 

[ozumo]

It could be any of a number of potential issues - alignment, LNBs, switch, cable, connectors or receiver. Where (roughly) are you located? I get all the FTA HD 19.2E channels with an offset LNB on a zone 2 Sky dish with a reasonable margin.

If it were alignment I'd expect you'd have issues on both sats, generally 13E is a bit weaker than 19.2E. You could try swapping the LNBs around to see if it makes any difference. If you do that remember to take a photo of the skew so it is similar when you move the LNBs.

When checking alignment a cheap sat beeper can be very useful as it gives instant feedback on general signal strength. Just pulling lightly east/west/north/south will be enough to discover if the dish alignment needs to be changed.

 

[Terryl]

Fade out during bad weather?? the only fix is a bigger dish, for every 8 cm larger in diameter dish you get about 3 dB of signal gain.

So up your 75 cm to a 1 meter dish, you might, and I mean might get an big improvement.

an app called ""dishpointer dot com"" will give you an idea on what size dish would work at your location.

 

[Bamboccio]

It could be any of a number of potential issues - alignment, LNBs, switch, cable, connectors or receiver. Where (roughly) are you located? I get all the FTA HD 19.2E channels with an offset LNB on a zone 2 Sky dish with a reasonable margin.

If it were alignment I'd expect you'd have issues on both sats, generally 13E is a bit weaker than 19.2E. You could try swapping the LNBs around to see if it makes any difference. If you do that remember to take a photo of the skew so it is similar when you move the LNBs.

When checking alignment a cheap sat beeper can be very useful as it gives instant feedback on general signal strength. Just pulling lightly east/west/north/south will be enough to discover if the dish alignment needs to be changed.

Thanks a lot for the detailed response.
I am in London.
I have two receivers and two cable runs going down and both have the issue so I would exclude cable and receiver.
I believe that the visiosat has two focal points (one with more signal than the other) and therefore one of the LNB / sat will get more signal. Looking at the dish front the front the LNB on the right (more est) which should point to 13?) is out of the centre while the other is more aligned to the centre. So in theory Astra should have the best gain.
if I swap the LNBs will I like mess the skew? I am even thinking to buy a new LNB so I do not touch Astra.
I will check how much a beeper is.

 

[Bamboccio]

It could be any of a number of potential issues - alignment, LNBs, switch, cable, connectors or receiver. Where (roughly) are you located? I get all the FTA HD 19.2E channels with an offset LNB on a zone 2 Sky dish with a reasonable margin.

If it were alignment I'd expect you'd have issues on both sats, generally 13E is a bit weaker than 19.2E. You could try swapping the LNBs around to see if it makes any difference. If you do that remember to take a photo of the skew so it is similar when you move the LNBs.

When checking alignment a cheap sat beeper can be very useful as it gives instant feedback on general signal strength. Just pulling lightly east/west/north/south will be enough to discover if the dish alignment needs to be changed.

Thanks I am in London.
I have two cable runs going to two different receivers so I would exclude that as the issue as both have the same problem. Is it true that the Visiosat has two focal points so one lnb is going to have more than the other?
In my case the lnb more to west (Astra?) is on centre so in theory I think that Astra should have more gain.
if I swap lnbs will I mess the skew?
I may just buy a new lnb soI do not touch hot bird.
I will also check the app and the price of the beeper.
I may send a photo of the dish later.

 

[Terryl]

For a dual LNB setup (looking at two birds) the dish should be looking in-between the two satellites, so the dish it's self will be pointing at 16.1, not 13 or 19.2.....This gets both LNB's the same amount of reflected signal from the dish, also the LNB's themselves should be offset mounted 3.1degrees off center, so no one LNB will be at true dead center.

 

[Terryl]

Also ""dishpointer . com"" has a selection for those two satellites, you enter your address, and select those satellites in the ""multi LNB"" section, this will give you the correct pointing information for your location, then just zoom into the location marker and click on it, you can move the marker to where you have the dish mounted.

 

[ozumo]

In London you should have no problem receiving both satellites on this dish.

Just to confirm is this the same as your dish?

https://www.amazon.co.uk/Visiosat-Bisat-G2-Grey-Smc-Parabolic-Antennae/dp/B001CJZJ72

Looking at it there is no central LNB, both are offset, and have adjustment for height to compensate for differences in elevation. It is possible there are multiple versions of the LNB holder so you may have an LNB in the centre, and one offset. A photo will help determine this.

When looking at the front of the dish the LNB on the right will be 13E, left will be 19.2E. You can confirm by putting a cloth over an LNB and checking which signal is affected.

Skew is the rotation of the LNB in its holder. When looking at the front of the dish the cable should roughly be exiting the LNB between (where an hour hand would be) 6 o'clock & half past six. If replacing or swapping the LNBs skew will need to be adjusted again.

Is reception from 13E OK? If so it does sound like the 19.2E LNB could be the problem. I assume both LNBs have two outputs? Make sure any replacement has at least two. A (non-Sky) 40mm universal twin or quad LNB should fit, though you may need one with a smaller feedhorn (the bit that faces the dish) so it does not get in the way of the other LNB.

 

[a33]

Is it true that the Visiosat has two focal points so one lnb is going to have more than the other?

In fact it would be a multifeed dish, that has a focal line (a line of focal points) instead of just one focal point. So which LNB is "central" is not important, in fact, with the G2 they are both equally offset from center (as written above).

The G2 bracket for 13E and 19E is I believe designed for France or central europe? So it might be that the distance between the LNBs is a bit greater than needed, and you have to find the best compromise for aiming the azimuth for the dish.
It could well be that you now have maximum reception for 13E and suboptimal reception for 19E, and that you'd have to find a new compromise for optimal reception of both satellites.
Is reception of 19E better, when you carefully push the whole dish a bit to the left (seen from behind the dish)?

Also, is the arm still firmly fixed to the dish?

Greetz,
A33

 

[Bamboccio]

Thank you to all.
the bracket is strong and fixed properly and I have no issues on hot bird.
I used the app and figured out that the skew was meant to be -14 for Astra and -10 for hot bird. I assumed that minus means rotating to the right (in clockwise direction). I moved it a bit straighter and now the signal is gone up to 97% from 84%! Photos show before and after. Now it’s sunny, so must wait for the rain to be sure 100%.
Am I missing anything?

 

[ozumo]

Yes the skew was in the wrong direction, a little bit more may help

11778 V 29500 (DW English HD) would be a good transponder to check. It is one of the more difficult to FTA transponders to receive due to the high 9/10 FEC.

 

[Bamboccio]

Argh I must have touched the height of the lnb and now I lost 11778 - it was 87% before now it’s zero. This is how it looks now. Any ideas?

 

[ozumo]

The height looks similar to the first pictures, in relation to the other LNB. Try returning the skew a little towards 6 o'clock.

P.S. Please be careful on that roof

 

[Bamboccio]

Thank you . I made a few tries but no signal when I search it. The funny thing is that on one receiver had the channel DW HD stored and I see it. So it must be a tiny amount that I miss?
This is how it looks now.

 

[sonnetpete]

I think you need to lower the left hand 'LNB'. Comparing the two pics, it's now above the other 'LNB' mounting screw. Height can be very important.

 

[ozumo]

it may be that the LNB has deteriorated somewhat which is why you began to lose HD channels when the clouds appeared. It's possible DW English HD was scanned in when the LNB was in better health.

Looking at the photos again, the LNBs look a little closer in the earlier pictures? As the holders look to be held with one bolt - it may be possible you rotated the 19.2E holder away from the 13E LNB? It may just be the angle of the photos as well.

edit: I agree with Pete, it looks higher in the last photo.

 

[a33]

[ So that is the G3A-bracket, for 13-19-28E, with (indeed) 19E about central....]

19E has 7.5 degree pre-skew, so skew for london = -7.5 (instead of -14).
13E has 3.535 degree preskew, it seems, so skew for london = -6.5 (instead of -10).
When looking into the dish, minus angle is indeed clockwise. (As the minus means anticlockwise, but seen from behind the dish, towards the satellite).

Greetz,
A33

 

[Bamboccio]

Thank you to al.

I have now made a bit of a mess

I will also try to adjust the height and reduce the skew.

 

[Bamboccio]

What a drama - I now have lost hotbird too

 

[Bamboccio]

I have got Hotbird back by skewing the LNB towards the right. I wonder if that is the correct direction then.