Splitting one Dish/LNB to two decoders. Correct splitter?

Forums › Freeview (DVB-T/DVB-S) › Splitting one Dish/LNB to two decoders. Correct splitter?

cgreenwood

201 posts

Master Geek

#91340 11-Oct-2011 20:31

I currently have freeview running off an ex sky Satelite dish (it has the sharp dual LNB) and one freeview decoder. Works well.

I wanted to split the signal to run a second freeview decoder from the same dish/LNB and so went to Mitre10 and bought this splitter:

Question the first: Is this the splitter I need? If not can you tell me what I do need?

I understand the LNB needs to be powered by one (but not both) of the decoders and if you have the power on for both it will not work. This splitter has a power path through but it seems that it is intended for use with masthead amplifiers on a UHF set up where the power would be coming from the mast head to the reciever and not the other way around. So:

Question the second: Should I connect the splitter in reverse to allow the power pass through? ie have the plug labled "From TV antenna" connected to the decoder suplying the power for the LNB?

I have to admit to being a bit stupid here and when I saw the F-connectors just assumed to would be suited for satelite systems, apparantly not.

Thanks

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#532118 11-Oct-2011 21:55

Have you tried it?

tangerz

625 posts

Ultimate Geek

#532120 11-Oct-2011 21:56

Yep that is the one you need! You don't need to use it in reverse. In a masthead amp situation power is fed UP TO the masthead amp by a power supply in the same way a satellite decoder feeds power UP TO the LNB.

You shouldn't have any problem having both decoders sending power to the LNB. If only one is setup to send power then it always has to be on for the other to work. Only problems you may have are if you were trying to access different polarities at the same time, (not a problem if you're only after Freeview)

F-connectors don't always mean satellite but the frequency range on this (5-2400 MHz) means it is suitable for satellite. VHF/UHF only ones are usually 5-950 MHz.

PimpMyMagic

267 posts

Ultimate Geek

#532121 11-Oct-2011 21:58

No. You don't need to reverse the splitter. In either case (LNB or masthead amp) the power is coming from the output end of the feeder and going to the masthead. In the case of a UHF masthead amp the power is injected from (usually) a small plug pack at the receiver end of your antenna connection. Any power pass output on your splitter is simply providing a DC path through to your co-ax, be it driving an Aerial amplifier or an LNB.

B1GGLZ

1961 posts

Uber Geek

#532130 11-Oct-2011 22:11

tangerz: Yep that is the one you need! You don't need to use it in reverse.

F-connectors don't always mean satellite but the frequency range on this (5-2400 MHz) means it is suitable for satellite. VHF/UHF only ones are usually 5-950 MHz.

I don't think so. It only goes to 2400mhz (2.4ghz) and freeview satellite is around 12.5ghz.
It's meant for UHF TV antenna.

B1GGLZ

1961 posts

Uber Geek

#532133 11-Oct-2011 22:15

B1GGLZ:

I don't think so. It only goes to 2400mhz (2.4ghz) and freeview satellite is around 12.5ghz.
It's meant for UHF TV antenna.

However having looked at the splitters and diplexers the Freeview Shop are selling they only go to 2450mhz so I guess I'm wrong?

nickb800

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#532140 11-Oct-2011 22:38

B1GGLZ:
B1GGLZ:

I don't think so. It only goes to 2400mhz (2.4ghz) and freeview satellite is around 12.5ghz.
It's meant for UHF TV antenna.

However having looked at the splitters and diplexers the Freeview Shop are selling they only go to 2450mhz so I guess I'm wrong?

You are both right and wrong. The LNB shifts the frequency down from 12ghz to more like 2ghz, so that its only 2ghz going down the cable to your decoder

tangerz

625 posts

Ultimate Geek

#532144 11-Oct-2011 22:42

B1GGLZ:
B1GGLZ:

I don't think so. It only goes to 2400mhz (2.4ghz) and freeview satellite is around 12.5ghz.
It's meant for UHF TV antenna.

However having looked at the splitters and diplexers the Freeview Shop are selling they only go to 2450mhz so I guess I'm wrong?

B1GGLZ, the LNB converts the satellite transponder frequency to an intermediate frequency (I.F.) for distribution on a coax cable. Don't think you'd send 12GHz very far on coax

For example: transponder frequency (say 12456MHz), minus LNB frequency (say 10750MHz) equals intermediate frequency (in this case 1706MHz)

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injuised

256 posts

Ultimate Geek

#532197 12-Oct-2011 08:01

tangerz:
B1GGLZ:
B1GGLZ:

I don't think so. It only goes to 2400mhz (2.4ghz) and freeview satellite is around 12.5ghz.
It's meant for UHF TV antenna.

However having looked at the splitters and diplexers the Freeview Shop are selling they only go to 2450mhz so I guess I'm wrong?

B1GGLZ, the LNB converts the satellite transponder frequency to an intermediate frequency (I.F.) for distribution on a coax cable. Don't think you'd send 12GHz very far on coax

For example: transponder frequency (say 12456MHz), minus LNB frequency (say 10750MHz) equals intermediate frequency (in this case 1706MHz)

too true, I have seen a system where they run the 12g straight from the LNA and distributed through fibre , great idea , but i dont think mr joe average has a spare arm or leg

richms

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#532234 12-Oct-2011 09:47

No diodes on that splitter so you will have problems backfeeding from one reciever into another. Look for diodes in the description of the splitter.

Richard rich.ms

tangerz

625 posts

Ultimate Geek

#532330 12-Oct-2011 13:23

richms: No diodes on that splitter so you will have problems backfeeding from one reciever into another. Look for diodes in the description of the splitter.

Are you sure richms? It would seem to me any splitter that had power pass, (be it on one or all ports), but no diodes, would be useless because as soon as you use the power pass all other outputs would be 'compromised' by the power backfeed? Hence rendering the 'splitter' to be a one input/one output... not really a splitter then huh? Or am I missing something?

richms

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#532335 12-Oct-2011 13:31

For normal RF use TV inputs etc block DC/low freq AC so will not be a problem when a masthead amp is powered from another socket. As mastheads use AC often (something to do with not rusting) they cant use diodes in the splitters for that.

Richard rich.ms

Jaxson

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#532345 12-Oct-2011 14:06

That is a very good point richms, so I think not shopping at mega for quality satellite parts would be a good start.

There are plentry around, - freeviewshop for example

tangerz

625 posts

Ultimate Geek

#532367 12-Oct-2011 14:48

richms: For normal RF use TV inputs etc block DC/low freq AC so will not be a problem when a masthead amp is powered from another socket. As mastheads use AC often (something to do with not rusting) they cant use diodes in the splitters for that.

Good to know! I guess all splitters aren't created equal then :) Is it easy to tell splitters with diodes from those without unless it is given in the description? (ie. Do they have diode markings on the power pass lines?)

richms

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#532386 12-Oct-2011 15:21

the ones I have seen had a diode symbol and said all ports diode power pass or something on them

Richard rich.ms

cgreenwood

201 posts

Master Geek

#532398 12-Oct-2011 15:33

Ok so what was the final verdict, I got a little lost along the way with the technical jargon.

Will this one be better?

http://www.freeviewshop.co.nz/satellite-terrestrial-splitter-p-55.html

Thanks

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