Lost some freesat channels since changing the LNB ?? Please help !

[admin_exported]

Hello all, Weve just added a second humax box to the original setup thus had to change the original which was only a singke to a quad but since doing this weve lost some freesat channels (bbc1 plus a few more) most others are ok bbc 2 itv etc2 , originally it was a single feed from a single lnb down to the humax now its 2 feeds to each box from a quad lnb and ive less channels. Please help, thanks.

 

[davejberry]

The simplesr answer would be that you've knocked your dish off line when you changed your LNB. You don't say where you live but where I am, when there is any hint of dish movement or the weather is really bad, BBC1 is always the first channel to go.

Another reason could be that you have a bad connection to the LNB or that the LNB itself is faulty; it is not changing polarisation, so you can only get the channels on horizontal not vertical transponders.It could also mean that your new LNB has a higher noise figure than the old one and this coupled with a badly aligned dish has dropped some of the channels below the threshold of your receiver.

Advice - check all the connections first. Then swap the cables to another output on the LNB as one or two outputs may be faulty. Then check your box on a friends dish. If all else fails, get out the ladders and re-align your dish (check your LNB has a noise figure of 0.3dB or lower

Hope this helps

Dave

 

[Anonymous]

When I put the single lnb back on all the channels including bbc 1 are there again, put the quad back on lose bbc1 again. Thanks for the advice Dave i'll try a new lnb i think unless there's anything else to try? Thanks.

 

[Dave_]

Is it an elliptical mini-dish you're using,i,e one thats mucher wider than it is tall as used by Sky etc,?

If so then make sure you have an LNB that is specifically for elliptical mini-dishes and not just a generic LNB meant for round(er) dishes supplied with an adaptor to fit a mini-dish.

You wont get optimum signal from using the later on mini-dish due to the shape of the scaler rings/steps in the feedhorn (the part of the LNB that collects/focuses the reflected satellite signals from the dish).

The scaling rings in an mini-dish LNB are elliptical too, as it has a wider dish area to focus on in the horizontal plane than it does in the vertical plane.The LNB's used on round(er) dishes have round scaling rings/steps because the focus area is virtually the same in both plane's, so if you was to use one on an elliptical dish it wont be focusing on the full dish area in said horizontal plane.Hope that makes sense.

Having said all that,and assuming you have the correct type LNB and it isn't faulty and all the connections are ok and the fact you get signal when you put the old LNB back on i'd put money on it being one of the following...................

Firstly, quad LNB's are usually considerably heavier than single LNB's.This can cause the dish/feed arm to sag,and it's not uncommon to have to adjust the dish elevation to account for the sagging.

Secondly, would be the LNB 'skew' is out. LNB skew/LNB polarization is basically the rotational posistion the LNB is mounted,in relation to to the dish. If this out you wont be getting optimum signal and can cause the symptoms yo describe, i.e particular channels missing,especially missing BBC's/ITV's.

Different LNB's have different ways/markings for Skew adjustment, but it's usually one of the following

The skew is adjusted by loosening the screws of the LNB holder and rotating the LNB in it's holder by a certain amount of degree's, the LNB will have a scale marking on it somewhere,usually underneath or on the side.

You can find the degree of skew you need to use by going to http://www.dishpointer.com/ entering your full address and then selecting the satellite(s), which is 28.2 East (Astra 2A,2B and 2D). Then at the bottom of the page you will see the dish set-up data, which will give you LNB skew adjustment, dish elevation and azimuth settings.

The other type of LNB's commonly found on mini-dishes have skew presets (marked 1-5) and is adjusted by loosening the single screw underneath and rotating the LNB in its weather casing. Without a satellite meter adjusting these type of LNBs is going to be a bit of trial and error, but it's just a case of getting the signal levels screen up on your STB and adjusting until you get the best signal strength/quality. I would recommend starting in the middle of the scale,so with a skew of 3 then adjusting from there.

HTH...

 

[Dave_]

davejberry:check your LNB has a noise figure of 0.3dB or lower

Going to have to disagree with you on that point Dave!!! The noise figure is unimportant imho.Largely because manufacturers claims are optimistc at best.......

The noise figures quoted are nearly always the lowest figure at a given frequency and not right across the spectrum, and can be considerably higher at different frequencies.

 

[davejberry]

daveh75:
davejberry:check your LNB has a noise figure of 0.3dB or lower

Going to have to disagree with you on that point Dave!!! The noise figure is unimportant imho.Largely because manufacturers claims are optimistc at best.......

The noise figures quoted are nearly always the lowest figure at a given frequency and not right across the spectrum, and can be considerably higher at different frequencies.

I agree with you daveh75. I didnt mention the lnb shape as I assumed that the OP had just asked for a 'sky dish lnb' at a satellite shop as is common in the UK. I only mentioned the noise figure as have recently replaced some lnbs where the noise figures were 0.6 and 0.9dB for some with 0.3dB (on 100cm dishes aligned with a good quality meter) and now have very happy customers because BBC has stopped disappearing when it rains. (we're not in the UK). My hope is that, between us we have helped the OP solve his problem 🙂

 

[Dave_]

davejberry:daveh75:
davejberry:check your LNB has a noise figure of 0.3dB or lower

Going to have to disagree with you on that point Dave!!! The noise figure is unimportant imho.Largely because manufacturers claims are optimistc at best.......

The noise figures quoted are nearly always the lowest figure at a given frequency and not right across the spectrum, and can be considerably higher at different frequencies.

I agree with you daveh75. I didnt mention the lnb shape as I assumed that the OP had just asked for a 'sky dish lnb' at a satellite shop as is common in the UK.Trouble is a lot of uk suppliers are now offering "very low noise" LNB's, such as Titaniam,Icecrypt,GI etc meant for standard dishes, with an adaptor for mini-dishesI only mentioned the noise figure as have recently replaced some lnbs where the noise figures were 0.6 and 0.9dB for some with 0.3dB (on 100cm dishes aligned with a good quality meter) and now have very happy customers because BBC has stopped disappearing when it rains. (we're not in the UK). My hope is that, between us we have helped the OP solve his problem 🙂Fair comment...... Im guessing from the dish size you're in mainland europe, so noise figures are probably going to be quite significant when receiving fringe reception from Astra 2D's spot beam. Not so much a problem for us in the UK where Astra 2d romps in.