DVB-S Siginal Woes

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Jaggy

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#123297 2-Jul-2013 17:00

I will start off by saying "I now hate digital siginals totally & completely" they have haunted me ever since I tried to receive them,
both DVB-S & DVB-T have eluded me getting really good reception!!! ....... OK that's my rant over.

I will start off with my DVB-S woes (& worry about the DVB-T woes another day).

I bought a new 900mm dish (a number of years ago now) in the hope I wouldn't have these signal issues for Freeview channels but I've always had them to some extent or other. I should also mention that we watch all our TV programs through a computer PVR (running GB-PVR or NextPVR) through NMT extenders at the TV therefore I'm trying to capture with three Haupauge tuner cards (2x HVR-3000's & 1x HVR-4000)

Up until recently I was using a dual LNB (for SBS) & we got glitches (almost always at the most critical part in the program) not often or for long but about three or four times in a one hour recording...., recently I get fed up with this & reverted to the single LNB that came with the dish & since then I have had full one hour recording without a glitch (Yea!!) or total failures that won't play basically at all (crap!!). I should also mention that about a year ago I replaced both the cables with new low hydrogen cables & apart from having a couple of curves that are on the tight side (which could affect the signal from what I've read) these cables still appear to be like new out at the dish.

Today I got up onto the roof to try tweaking the dish/LNB (& discovered the dish has some lichen on it which I have now treated with 60minute remover...which tells me I should leave on for a couple of days....how the hell can they call it 60minutes??) & found that the basic alignment seems to still be fine (as-in it drops signal in all directions when I flex the dish) altering the skew does make a difference but only to the TVNZ transponder not the other transponder which is sitting really low on quality & it the channels on this transponder that we watch the most (Prime, Choice, TV3 & CUE) that have had the failures.... the attached image is what I now get after today's effort with ProgDVB & a Twinhan card

I'm totally at a loss where to go to from here..... any ideas, thoughts or comments??

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#848338 2-Jul-2013 17:05

Hi, to say that the skew makes no difference is not right, to set this correctly you really need to do a cross pol alignment and null the off pol transponders. What C/N are you getting, you will need a proper meter with spec analyser mode to do both of these.

Cyril

RunningMan

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#848341 2-Jul-2013 17:11

With a 90cm dish there should be a really good signal with lots of margin for slight misalignment and weather conditions. It should be almost never dropping out at all.

A common cause of intermittent problems, and particularly ones that seem to show up at about the same time each day is a failing LNB. They often get temperature sensitive with age and if they get too hot or cold, the LO frequency drifts out, and the signal drops because the tuner can't keep a lock on it. Obviously, the fix is a new LNB.

What sort of plugs do you have - are they watertight, corrosion free etc.?

What exactly happens when you see the problem? Do you have a normal STB you can test with instead of the HTPC, just to rule out any software or hardware issues with that?

KiwiTim

376 posts

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#848572 3-Jul-2013 09:50

As far as DVB-T picture goes, don't blame pixilation on poor quality reception, it may well be a problem with your Hauppauge DVB-T tuners. I have a Nova TD500 and HVR-3000. Both of them are very sensitive to EMI. It pays to have a full ATX board that has plenty of space between the PCI slots, or have unoccupied slots. Also, low power can cause pixilation.

I ended up buying a new case and a bigger power supply, which fixed the problem with the HVR-3000, but I still have trouble with the Nova-TD 500 on my mATX motherboard. The latter device works perfectly on a full ATX motherboard.

I have heard that there are other brands of DVB-T devices less temperamental than Hauppauge, but I haven't tried them.

Jaggy

32 posts

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#848613 3-Jul-2013 10:33

Hi Cyril & thanks (I think) for your reply...,

cyril7: Hi, to say that the skew makes no difference is not right,

What I really was referring to was changing it had no noticeable affect on the non-TVNZ quality figures (which looks pathetically low to me... but I have no idea if it should be better than in the screenshot I posted yesterday but I suspect it should be WAY better) until I moved it around to about the 8:30 position (as viewed from the front looking back at the dish) then the quality dropped.... but the quality for the TVNZ transponder got steadily better as I rotated the LNB back to about the 6:00 position (which really confuses me as all I have read says it should be skewed for NZ Freeview channels??)

to set this correctly you really need to do a cross pol alignment and null the off pol transponders.

I have no idea in the least what this means or what needs to be done to achieve whatever it is you are trying to say??? I am just a layman with a little/tiny/small knowledge on this stuff.

What C/N are you getting,

Again no idea what "C/N" is referring to.... this is not one I have ever heard before...

you will need a proper meter with spec analyser mode to do both of these.

I do realise to achieve a 100% alignment it requires a "$-many hundreds" meter but it seems to me as I'm not attempting to pull in a marginal signal & the dish I have should be "way big enough" it shouldn't need to be 100% (& I have read about a lot of other that have done it without an expensive meter or getting it done professionally) for me to get good recordings.

Jaggy

32 posts

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#848616 3-Jul-2013 10:36

RunningMan:With a 90cm dish there should be a really good signal with lots of margin for slight misalignment and weather conditions. It should be almost never dropping out at all.

Which was exactly my thought in the first place & I really don't want to have to keep cocking around with the dish all the time.... I'm not even sure for how many more years I will be capable of getting up on the roof.

A common cause of intermittent problems, and particularly ones that seem to show up at about the same time each day is a failing LNB. They often get temperature sensitive with age and if they get too hot or cold, the LO frequency drifts out, and the signal drops because the tuner can't keep a lock on it. Obviously, the fix is a new LNB.

That's possible... & it is also possible that the dual LNB I got (off TradeMe) was just a crappy LNB.... odd thing is Sunday evening The Bosses Trade Wars (Prime) failed completely but Antiques Roadshow (also Prime & right after TW) was 99.99% fine??

What sort of plugs do you have - are they watertight, corrosion free etc.?

Errr I think they are called compression ring fittings or something like that, the ones out at the dish are as supplied with the cable when I got it, the ones in at the splitter are the ones I fitted & I believe they are Sky approved fittings.... they still look like new but it is possible that, even though I can't see any, there is a little corrosion on the LNB as in the past I lost the marginal signal I had been getting & when I checked the dish I found that the end was just a screw on F connector & it was badly corroded...., also when I cut off the end to fit a new connector the cable kept breaking (as in really really badly gone hard in the sun) & this is when I decided to new low hydrogen cables.... this has also made me wonder how good a quality the supplied LNB actually is??

What exactly happens when you see the problem?

We are getting total 98% pixilation in between totally blank screens, like totally unplayable for the whole recording.... which sort of surprises me as when it not like this it's 100% fine??

Do you have a normal STB you can test with instead of the HTPC, just to rule out any software or hardware issues with that?

No DVB-S STB, Money is really tight for us ever since I had to give up work a number of years ago due to illness & I can't justify spending any of it on something that won't be used.. but I do have two totally separate computers with different brands of DVB-S cards (Hauppauge for the HTPC & Twinhan for my PC) & both are giving the same results which should basically rule out software/hardware at the PC end I feel.

Jaggy

32 posts

Geek

#848620 3-Jul-2013 10:46

KiwiTim: As far as DVB-T picture goes, don't blame pixilation on poor quality reception, it may well be a problem with your Hauppauge DVB-T tuners. I have a Nova TD500 and HVR-3000. Both of them are very sensitive to EMI. It pays to have a full ATX board that has plenty of space between the PCI slots, or have unoccupied slots. Also, low power can cause pixilation.

I was going to keep away form my DVB-T problems at the moment & concentrate on DVB-S first, but as some of it crosses over.... I do have an "old" full ATX mobo in the HTPC but not any free slots as it currently has five tuners in it.....

I ended up buying a new case and a bigger power supply, which fixed the problem with the HVR-3000, but I still have trouble with the Nova-TD 500 on my mATX motherboard. The latter device works perfectly on a full ATX motherboard.

I have also seen the low power problem in the past very noticeable one of the times the PSU was on the way out, therefore the last time it decided to die time I fitted a good quality more grunty PSU.

I have heard that there are other brands of DVB-T devices less temperamental than Hauppauge, but I haven't tried them.

I do know that the Nova-TD500's do have a driver problem with Win7 which can cause glitching

trig42

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#848680 3-Jul-2013 12:23

You haven't got anything getting in the way of the dish have you (big trees etc.)?

I would re-terminate your cables, just to make sure a little strand of the shielding is not touching the inside wire on the coax.

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Jaggy

32 posts

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#848705 3-Jul-2013 13:12

trig42: You haven't got anything getting in the way of the dish have you (big trees etc.)?

Damn I was going comment on this before just so everyone knew but old age crept in again & I forgot..... there is nothing in front of the dish, it has a nice clear line of sight right up the road..

I would re-terminate your cables, just to make sure a little strand of the shielding is not touching the inside wire on the coax.

That's way easier said than done with the compression fittings type ends, the ones outside are commercially done so "technically" should be OK (I guess) & I was very careful with the ones I did.... also there are two cables (even though I'm only using one right now) & they both were exhibiting the same/similar problems when I had the dual LNB in place.... Oh yeah I should also point out that at that time one cable was going to the splitter & the other directly to a card but both still had reception problems..... I could drag out the sun-hardened cable (which is still sitting in place in the roof & see if it's long enough to re-make off with a new screw on F connector as a trial I guess

illicit

553 posts

Ultimate Geek

#848729 3-Jul-2013 13:26

There could be a number of issues, at any point from dish to receiver (alignment, crimps, cable, splitters etc)

Without the proper test equipment - you are only guessing (Signal info on receivers is not accurate enough to trouble shoot)

Good luck, but I recommend finding a good tech and spend $100 on getting done right once and for all

B1GGLZ

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#848760 3-Jul-2013 13:55

So far everything seems to be pointing to a LNB that is weak and failing.
Try a new LNB and sounds like you might need new cabling too.

Jaggy

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#848788 3-Jul-2013 14:43

Without the proper test equipment - you are only guessing (Signal info on receivers is not accurate enough to trouble shoot)

Oh I do agree with you up to a point, I was hoping that the fact that the TVNZ signal (seems to me) is good & the non TVNZ is so bad would give a clue to someone as to where the problem lies... if I really "have to" I will spend the dollars & get someone to look at it but dollars are really tight for us & can only be spent once.

I do just happen to have a new LNB from a second never fitted dish sitting here that I will try out soon... I also a new professionally made cable that came with it that I can try out by dropping it from the roof through the window for test purposes.... I will be more than hacked off if there is something wrong with the "really damned expensive" approx one year old low hydrogen cables though.

Jaggy

32 posts

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#848791 3-Jul-2013 14:47

Oh one other thing I forgot.... just how important is getting the skew "just right" to the signal???

The reason I ask is the cheap signal meter doesn't seem to vary much at all when playing with the skew & getting up & down on & off the roof to have a look at the meter on the computer when there is only one of you is a right royal pain.

B1GGLZ

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#848837 3-Jul-2013 16:02

Oops. Jus re-read your earlier post. I thought it was the new cable had gone hard but it was the old one.
The new ones should still be fine so I'd be looking at changing the LNB first.
When LNBs are failing they usually drift off frequency. Have you tried adjusting the freq up and down in your STB setup?

Brunzy

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#848851 3-Jul-2013 16:45

Jaggy:
Without the proper test equipment - you are only guessing (Signal info on receivers is not accurate enough to trouble shoot)

Oh I do agree with you up to a point, I was hoping that the fact that the TVNZ signal (seems to me) is good & the non TVNZ is so bad would give a clue to someone as to where the problem lies... if I really "have to" I will spend the dollars & get someone to look at it but dollars are really tight for us & can only be spent once.

I do just happen to have a new LNB from a second never fitted dish sitting here that I will try out soon... I also a new professionally made cable that came with it that I can try out by dropping it from the roof through the window for test purposes.... I will be more than hacked off if there is something wrong with the "really damned expensive" approx one year old low hydrogen cables though.

Can I ask where you got these , I have never heard of this & I use RG6 on a daily basis.
Bog standard Rg6 is fine for DVB S.

B1GGLZ

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#848862 3-Jul-2013 17:00

Brunzy:

Can I ask where you got these , I have never heard of this & I use RG6 on a daily basis.
Bog standard Rg6 is fine for DVB S.

+1
Oxygen free cables are available but I've never heard of Low Hydrogen cables.
Googling Low Hydrogen co-ax brings up nothing.
Wiki talks about using Oxygen Free Copper cable to resist Hydrogen Embrittlment.

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