Sky +

sausage butty · 25-06-2009, 18:41

Hi we have just had sky hd + installed the sky engineers put up a double lnb on the dish and ran an extra cable to it .i understand why they do this but surely there must be a way of using just one cable and duplicating the signal when it gets to the box , it would save a lot of hassle. does anyone know if its possible?

entwisi · 25-06-2009, 19:05

its usually a twin cable fastened together. have they not replaced teh original one?

sausage butty · 25-06-2009, 19:09

yes they replaced it for a twin but what im sayin is why do they need to send the exact same signal down twice? for all other electrical signals i can think of you can duplicate it or "split it" why cant this be done on the sky signal?

entwisi · 25-06-2009, 19:15

you can record two seperate channels, these could potentially be on both horzontal and vertical polarised channels so you need an LNB feed for each.

Neil · 25-06-2009, 20:36

The LNB can actually receive a wide range of frequencies in both horizontal and vertical polarity (circular polarity is used on some satellites). The LNB converts the signal you require to view into a lower frequency that can be transmitted done the cable to your box. You have 4 choices, horizontal and vertical on both high and low band - it can only convert one of the 4 at once and send it to the box. That is why you need 1 cable per receiver.

It is possible to use 1 cable but you need expensive equipment. It is easier and cheaper to use a standard quad lnb with 4 outputs and a cable for each receiver.

mattylad · 25-06-2009, 21:46

Also it is not exactly the same signal, the signals can be different, on different frequencies.

It's a quad LNB that you will have, so now you have the ability to tag on 2 extra feeds to feed to 2 more ordinary boxes or another sky+ box that you use on Freesat.

sausage butty · 27-06-2009, 16:12

just found this

The correct answer Is given to you by John C however he has put it in rather complicated terms for the layman to understand . So this is it in basic terms . On the Dish you have a device called an LNB it is basically a microwave receiver , now some signals are vertical and some are horizontal , now what this means is inside the LNB there is a component that electronically changes its direction to collect the signals Ie: Vertical or Horizontal . to do this it applies either an 18volt positive to negative voltage or a 13 volt negative to positive voltage . now in the end of the sky LNB there are two LNB's joined together one for each tuner hence two cables. applying a different voltage for each channel .

and btw i definatley have a twin lnb and not a quad.

Neil · 28-06-2009, 14:19

Quote:

Originally Posted by sausage butty

applying a different voltage for each channel .

and btw i definatley have a twin lnb and not a quad.

The voltage bit there is a little misleading, there is not a seperate voltage for each channel. The voltage is to select polarisation, hi or low band is selected using a tone sent up the cable to the LNB