powering LNB

I have a satellite dish and the signal splits 3 ways

1 to sky box
2 to separate tv and free view box
3 to a further tv and free view box

When the skybox power is on, I get tv on the other freeview box systems because the LNB is powered up from the sky box. However when the sky box is off there is no signal at the other locations.

The free view boxes are SUPERVIEW brand.
is there any way I might be able to fix this situation.

David

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Permalink Reply by Biggles on April 18, 2018 at 9:09

Problematical. You need to make sure that the 3 way splitter is power pass on all ports but you should really only power the LNB by one device at a time. That means of course that either one box must be on all the time (others with LNB power set to off) or you need to power the LNB with one of the boxes that is on. You could perhaps check with an installer to see if you can get a splitter fitted that supplies power to the LNB from the splitter rather than from the STBs.

Easiest and cheapest solution is don't turn ever the Sky box off. It doesn't use much power. When I had Sky I never ever turned the box off. Likewise I never turn off my Panasonic recorder. They take ages to boot up anyway.

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Permalink Reply by willis on April 18, 2018 at 12:09

An all port power pass splitter lets lnb power through via diodes stopping power going backwards

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Permalink Reply by Biggles on April 18, 2018 at 13:35

Thanks Willis. I didn't know that as I can't find a circuit for one anywhere. For once google isn't my friend.

So all that's needed then is a 3 way all port power pass filter and turn on LNB supply in all decoders? Still doesn't help with polarity switching though I guess?

I'd still go with just leaving the Sky box on all the time. Cheap and easy solution.

willis said:

An all port power pass splitter lets lnb power through via diodes stopping power going backwards

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Permalink Reply by David Lipscombe on April 18, 2018 at 16:31

This is one that I use right now and it does the job:-

http://www.freeviewshop.co.nz/input-output-satellite-multiswitch-p-...

I have 2 feeds going out , 1 is direct to a sat box and the other feed goes to a 1in/6 out box which feeds a sky box and 3 sat boxes

or you could get one like this which would do the job

http://www.freeviewshop.co.nz/satellite-terrestrial-splitter-p-493....

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Permalink Reply by David Edmunds on April 19, 2018 at 7:05

Thanks for the very good feedback. I have a splitter just like the ones referred to. The complication I have is that the skybox I refer to is sometimes turned off and I do not have access to it it to have it switched on again. My splitter has full pass though for voltage. One thing I am aware of is that it is prudent not to have more than one top box supplying the LNB However the Freeview top boxes don’t seem to have an option to turn off this voltage supply which I assume is 18V. Interestingly they do have a separate option to turn a 12V option on or off but not sure what this would be for?

Notwithstanding the above I wonder why when the sky box is off that the Freeview box is not just supplying the voltage required and the LNB remains on. Maybe my Freeview box is for some reason not supplying the power as required. Can I measure the voltage from the Freeview box at the splitter at the coaxial cable end? I assume it is 18V DC. Does anyone know the tolerance on this voltage eg would it still work if voltage was say 15V due to cable length and volt drop?

thx

D

David Lipscombe said:

This is one that I use right now and it does the job:-

http://www.freeviewshop.co.nz/input-output-satellite-multiswitch-p-...

I have 2 feeds going out , 1 is direct to a sat box and the other feed goes to a 1in/6 out box which feeds a sky box and 3 sat boxes

or you could get one like this which would do the job

http://www.freeviewshop.co.nz/satellite-terrestrial-splitter-p-493....

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Permalink Reply by Biggles on April 19, 2018 at 8:48

Yes. You should be able to measure the voltage out from the STB on the co-ax.

It should be 18v for Horizontal polarisation (Freeview/Sky) and 13v for vertical polarisation. As far as I can tell only the feed channels on Optus D1 are vertical.

Their must be somewhere in the setup menu where you set LNB voltage. Check the menu for LNB Power. You should be able to select something like 13/18v, 13v, 18v, and off if it's anything like my setup menu. It should be set to either 18v or 13/18v. What Make and model are the STBs?

Also confirm that ALL ports on the splitter are power pass? WHat make and model is the splitter?

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Permalink Reply by Satellite Networks Motueka on April 19, 2018 at 15:29

Thats a 3x4 multiswitch not a splitter. Use the 18v port and dont turn off the LNB power in the other STBs. If you turn the power off in all but one STB then you will lose all signal when that STB is turned off. Also the splitters are diode steered so the power wont go back down the cable.

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Permalink Reply by David Edmunds on April 22, 2018 at 7:20

What is the difference between a multi switch and a splitter? I am starting to think that my Freeview box is not putting out the 18V or that the voltage when it gets to the LNB is less than 18V due the length of the run. I think I need to measure these voltages and see whether that is the problem. I will measure at the splitter first.

Satellite Networks Motueka said:

Thats a 3x4 multiswitch not a splitter. Use the 18v port and dont turn off the LNB power in the other STBs. If you turn the power off in all but one STB then you will lose all signal when that STB is turned off. Also the splitters are diode steered so the power wont go back down the cable.

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Permalink Reply by John Baird on April 22, 2018 at 8:14

Why don’t you swap the sky and one free view box and see if the results are the same or only works from the skybox, will eliminate different run distances ( which is unlikely)