LNB power tones etc

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allstarnz

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#19105 5-Feb-2008 15:44

Some questions for those such as Cyril7...

1 - Am I correct that only one LNB should ever be supplying power to the LNB? Should that decoder be turned off, will the other ones still work?

2 - Baring in mind that (I assume) only one box can supply power to the LNB, is it ok to have the dual LNB setup (ie parameters for D1 and C1) configured on the boxes not supplying power to the LNB?

3 - Can the 22khz tone be sent from a non-powered box, and if so will it have any effect

4 - Am I best to have the Sky box or freeview device powering the LNB ?

5 - If I want to access C1, I am best to have that device doing the powering and toning?

Hope this all makes sense.

My setup if it makes any difference is

                            |-------- Sky Box (power on, TBC)
                            |
Sky Dish ------------| (unknown splitter type)
                            |
                            |             |------ Freeview Box (non powered side)
                            |------------|
                                            |------ Sky Box (powered side, power turned off)

cyril7

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#108727 5-Feb-2008 16:27

Hi, only one STB should power the LNB. Normally splitters come in two types, ones that only have one power pass port and ones that have diode steering. I the latter case the STB that has the higher voltage (by approx 0.6V) will be the one that supplies the current to run the LNB.

Hpol is 18V, Vpol is 13V, so if you have the sky box supplying power (with a diode streer splitter) then even if the FTA box requested a Vpol signal it would be ignored as the Sky box would override it.

As for 22kHz, sky currently does not use any C1 capacity, and I doubt it ever will as this is only intended as a planB if D1 passes away. Normally a splitter port that will not pass DC will also not pass 22kHz as the coupling caps in the non DC path are designed to pass 5Mhz or greater, but 22kHz will most likely see too much loss to be heard by the LNB.

So if you want to have your FTA box see C1 then I suggest that you ensure that its on a DC passing port to the LNB, and naturally you will find that your Sky Boxs will see no signal while your FTA box is looking at C1 via a Sky dual throat single output LNB.

If you want full D1/C1 flexibility, they you will need to upgrade your dish to a 85-90cm one, install a dual LNB plate with two LNBs, the one looking at D1 need only be a single output LNB, the C1 LNB would need to be dual output, and connect this to a multiswitch. This will allow each each port of the multiswitch (the come in 4, 8, 12 16 outputs) to select whatever polarity and orbit location it likes without effecting other STBs.

From my perspective concidering the material on C1 that currently available, I would not bother with the expense, but your view may differ.

Cheers
Cyril

eXDee

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#108743 5-Feb-2008 17:35

While talking of sky pointing at C1, we have one of those D1/C1 single sky LNBs, would this only be able to pick up C1 or D1, or both at the same time from a DVB-S card for example?

cyril7

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#108752 5-Feb-2008 17:57

The Sky Sharp dual throat 156E/160E LNB is a single output LNB that switches to the west orbit location (156E/C1) when 22kHz is supplied. However as it only has one output you can not use it to see both orbit locations at the same time.

Cyril

allstarnz

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#108819 5-Feb-2008 23:23

thank you for that info, I think I now understand it more. If i figure out more questions, i'll add it to here

BarTender

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#108827 6-Feb-2008 00:51

The same also applies to the Horizontal and Vertical frequenceis as well.. So for example if you wanted to watch Imparja on D1 (Vertical), no one else in the house would be able to watch Sky or anything else that wasn't on the V pol, since the STB that is powering the LNB changes from 18v to 14v (or is it the otherway around, I always forget :), and like switching to C1, your Sky/Freeview world disappears... until you switch back to D1 Horizontal.

The only way around this as Cyril rightly said is to get the dual LNB plate with a 80CM+ dish. If you want to get H&V on a single satellite you need a dual output LNB, then do some fancy switching with a Diseq switch.

cyril7

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#108841 6-Feb-2008 08:57

And a final note, the reason Sky get away with a 65cm dish and a dual orbit arrangement is that the Sharp dual throat LNB has its two waveguides very close together, much closer than you can acheive by placeing two standard LNBs side by side. Thus you need a 80+ to obtain a greater focal length and thus wide diversion.

Cyril

allstarnz

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#109101 7-Feb-2008 16:17

thanks again, I am even more enlightened. I'm glad DVB-T won't be this complicated