Splitting DVB-S signal, does it degrade?

Forums › Home Theatre (including HTPC and EPG Collector) › Splitting DVB-S signal, does it degrade?

reven

3748 posts

Uber Geek
+1 received by user: 874

Trusted

#91703 19-Oct-2011 16:12

My sky signal has become flaky/choppy, and its after I added a split on one cable from my satellite and then added another 4 way splitter on that split.

i have 2 feeds from my satellite. one feed going directly into a my sky hdi box, and another feed going to a 2 way splitter. that two way splitter goes to another my sky hdi box and the other to a 4 way splitter that goes to a quad DVB-S2 card.

both my sky boxes and my dvb-s2 quad card are experiencing chopping video (we thought it was a tree in the way so we got a sky guy to come and move the dish, which hasnt fixed it). this isnt happening always but a lot more on the feed directly into the sky box (ie the line not being split)

i assumed since it was digital splitting it wouldnt have much of an effect.

so could splitting the signal have caused this? im using these splitters

http://www.trademe.co.nz/electronics-photography/tvs/satellite-receivers/auction-415059965.htm

http://www.trademe.co.nz/electronics-photography/tvs/satellite-receivers/auction-415957850.htm

TIA

richms

29098 posts

Uber Geek
+1 received by user: 10208

Trusted

Lifetime subscriber

#535229 19-Oct-2011 16:45

Yes, each run of cable sets up reflections back and forth, the more splits you have the worse it gets. Try putting an amplifier on the output that goes to the second splitter, that should clean up other stuff on the first splitter as it will not have crap coming back in from the second splitter.

Richard rich.ms

CYaBro

4708 posts

Uber Geek
+1 received by user: 1182

ID Verified

Trusted

#535257 19-Oct-2011 17:21

When you say you have two feeds from the satellite, does the LNB actually have two, or more, outputs on it?
If it is actually two seperate cables directly from the LNB then I wouldn't think that the one cable being split would affect the other cable.
COuld it be a faulty LNB?

Opinions are my own and not the views of my employer.

Niel

3267 posts

Uber Geek
+1 received by user: 80

Trusted

#535273 19-Oct-2011 17:41

For passive splitters:
With a 2-way split, each split see half the signal. With a 4-way split, each split sees 1/4 signal. So a 4-way split after a 2-way split, each 4-way split sees 1/8 signal. Every time the signal is halved you will see 3 dB drop (or is it 6?). There will be reflections on splits that are not plugged into a receiver, virtually no reflection where it is plugged in.

For active splitters, virtually no degradation.

You can never have enough Volvos!

Jaxson

8172 posts

Uber Geek
+1 received by user: 1332

Trusted

#535275 19-Oct-2011 17:43

and make sure you've capped any un used splitter outputs with a resistor, especially if they run into leads to wall sockets that aren't being used etc.

richms

29098 posts

Uber Geek
+1 received by user: 10208

Trusted

Lifetime subscriber

#535309 19-Oct-2011 19:13

CYaBro: When you say you have two feeds from the satellite, does the LNB actually have two, or more, outputs on it?
If it is actually two seperate cables directly from the LNB then I wouldn't think that the one cable being split would affect the other cable.
COuld it be a faulty LNB?

They are just a multiswitch on the same board as the LNB, so I dont see why it would be any different to any other splitter.

Richard rich.ms

reven

3748 posts

Uber Geek
+1 received by user: 874

Trusted

#535416 20-Oct-2011 07:34

there is two cables coming off the pointy part of the satellite dish and those two cables go to the two different rooms, one of those cables is never split again and that cable is suffering the choppyness aswell.

Niel: For passive splitters:
With a 2-way split, each split see half the signal. With a 4-way split, each split sees 1/4 signal. So a 4-way split after a 2-way split, each 4-way split sees 1/8 signal. Every time the signal is halved you will see 3 dB drop (or is it 6?). There will be reflections on splits that are not plugged into a receiver, virtually no reflection where it is plugged in.

For active splitters, virtually no degradation.

are those splitters i linked to passive or active? "active splitter" came up with no results on trademe, so not sure if they have a different name or not.

i know the easy way to test is just to unplug the split, but once i confirm that is the problem how can i go about fixing it? I have a sky guy coming friday to look at it, but not really keen on him seeing my HTPC setup (not sure how they react to this...)

would 3 cables from the dish be better than splitting the cable at the 2 way split? i would still need to split at the 4 way split, so have I'll then have 1, 1, 1x4. But the puzzling part is why the signal that isnt being split suffering the choppyness now.

Geekzone

Want to support Geekzone and browse the site without the ads? Subscribe to Geekzone now (monthly, annual and lifetime options).

trig42

5889 posts

Uber Geek
+1 received by user: 2094

ID Verified

#535432 20-Oct-2011 08:31

If you remove the 4-way splitter, does the signal improve?

Fraktul

836 posts

Ultimate Geek

Trusted

#535444 20-Oct-2011 08:51

Niel: For passive splitters:
With a 2-way split, each split see half the signal. With a 4-way split, each split sees 1/4 signal. So a 4-way split after a 2-way split, each 4-way split sees 1/8 signal. Every time the signal is halved you will see 3 dB drop (or is it 6?). There will be reflections on splits that are not plugged into a receiver, virtually no reflection where it is plugged in.

For active splitters, virtually no degradation.

Half of the original would be a -3dB delta.

richms

29098 posts

Uber Geek
+1 received by user: 10208

Trusted

Lifetime subscriber

#535452 20-Oct-2011 09:20

its more like 4.5dB on a 2 way splitter, and 8dB on a 4 way, there are losses, and then you have connector losses too.

Try looking for an "amplified splitter" instead, but its critical that they have the right freq range, unlike the passive ones.

Richard rich.ms

Niel

3267 posts

Uber Geek
+1 received by user: 80

Trusted

#535938 21-Oct-2011 06:34

Fraktul:
Niel: For passive splitters:
With a 2-way split, each split see half the signal. With a 4-way split, each split sees 1/4 signal. So a 4-way split after a 2-way split, each 4-way split sees 1/8 signal. Every time the signal is halved you will see 3 dB drop (or is it 6?). There will be reflections on splits that are not plugged into a receiver, virtually no reflection where it is plugged in.

For active splitters, virtually no degradation.

Half of the original would be a -3dB delta.

The dB scale has no units. It depends if you work with V or W. For example on audio mixing consoles -6dB is half the volume (actually -10dB is perceived as half, but -6dB is true half). I'm an electronic engineer, don't know (or care) what is used for satellite installations, but would expect marketing guys to want to quote a 2x gain at +6dB not +3dB so there is probably a mix of both voltage and power specs floating around.

You can never have enough Volvos!

reven

3748 posts

Uber Geek
+1 received by user: 874

Trusted

#535975 21-Oct-2011 09:05

trying to reproduce this issue constantly is a PITA, it seems to do it at random times, but when it does it, its terrible.

Doesn't seem to matter if I'm recording lots of shows at once (I thought that might be it), doesn't seem to matter if it's HD channels or not. So what I have so far is, its random, it effects every tv and not just the ones after the split. Not sure if removing the split fixes it, whenever I try to test that I cannot get it to go choppy. Sky guy is coming this morning, so hopefully he can figure it out.

But to confirm a tv not on the line that is split and feed directly into the satellite can be effected by the split? Where the satellite has two cables coming out its LNB?(i think thats what its called) and one feed goes directly from that to the tv.

HP

Shop now for HP laptops and other devices (affiliate link).

Brunzy

2019 posts

Uber Geek
+1 received by user: 241

Trusted

#536129 21-Oct-2011 13:45

Unless you have contibuted to the signal loss , say a faulty splitter ,or poor connection,
then it sounds like the dish is not aligned for max signal if it is dropping out on the HD box coming straight from the dish.
I am fairly sure Sky have reverted back to single O/p LNB's so just be aware that when it is eventually replaced , you will have to reconfigure your setup

reven

3748 posts

Uber Geek
+1 received by user: 874

Trusted

#536138 21-Oct-2011 14:14

Brunzy: Unless you have contibuted to the signal loss , say a faulty splitter ,or poor connection,
then it sounds like the dish is not aligned for max signal if it is dropping out on the HD box coming straight from the dish.
I am fairly sure Sky have reverted back to single O/p LNB's so just be aware that when it is eventually replaced , you will have to reconfigure your setup

yup the problem was the receiver on the sky dish, the guy came and sorted it, didnt think it could be the split since the unsplit feed was also screwy (just happened around same time which is odd). so now i can watch the RWC final without stutter, awesome :)

thanks guys for all the help :)