DVB "no signal" lost for a second - could it be Tuning / LNB voltage interference ?

[schussel]

Hi,

hope this is OK place for a somewhat technccal question. my setup:

• Twin LNB on a 70cm dish, Astra 13°E (mostly) from South Germany [this make]
• Sony TV , built-in DVB-S2 tuner
• Windows PC, USB based Pinnacle_PCTV_461e

When I turn on the TV, sometimes after some 10 to 30 seconds maybe, the signal is lost for 1-2 second, then back again.
Also I noted, when I schedule to record DVBV-s2 on the PC, at the moment the recording starts (which in case may require a change in station / tuning) , the DVB signal / picture on my Sony TV is lost for 1-2 seconds.

So I was wondering the reason fro such interference. Do I need to change a specific hardware / tuning setting on my PC ? (the TV has no config options of course)

I mean, it's not a big issue, but remains strange (or may put strain on the equipment).
Thanks -s

 

[deeptho]

Hi,

hope this is OK place for a somewhat technccal question. my setup:

• Twin LNB on a 70cm dish, Astra 13°E (mostly) from South Germany [this make]
• Sony TV , built-in DVB-S2 tuner
• Windows PC, USB based Pinnacle_PCTV_461e

When I turn on the TV, sometimes after some 10 to 30 seconds maybe, the signal is lost for 1-2 second, then back again.
Also I noted, when I schedule to record DVBV-s2 on the PC, at the moment the recording starts (which in case may require a change in station / tuning) , the DVB signal / picture on my Sony TV is lost for 1-2 seconds.

So I was wondering the reason fro such interference. Do I need to change a specific hardware / tuning setting on my PC ? (the TV has no config options of course)

I mean, it's not a big issue, but remains strange (or may put strain on the equipment).
Thanks -s

I bet it is the LNB.

I have had similar problems many times due to bad or badly designed LNBs, even new ones. One port causes a voltage increase or decrease on the other port (which should not happen) and that causes a glitch. Sometimes replacing the LNB with a brand new one of the same brand was not a solution, but when replacing with another brand the problem went away.

These problems can also affect some frequencies or bands more than others.

 

[schussel]

Thanks. Yes most likely.
I thought maybe some config on my end might help improve it.
E.g. my PC DVB-tuner (USB connected) would require an external 12V supply to properly work - which I guess is related to the voltage (and resistance) required to control the LNB, via a 20-25m Coax cable. There's settings on how to supply (or not) the LNB , etc. so I thought specific config might be required if multiple "consumers" connect to the same LNB.

 

[rolfw]

It could also be 22khz switching temporary bleed over, best way to stop that is use a quad and use the two oppsite ends of the LNB.

 

[deeptho]

Thanks. Yes most likely.
I thought maybe some config on my end might help improve it.
E.g. my PC DVB-tuner (USB connected) would require an external 12V supply to properly work - which I guess is related to the voltage (and resistance) required to control the LNB, via a 20-25m Coax cable. There's settings on how to supply (or not) the LNB , etc. so I thought specific config might be required if multiple "consumers" connect to the same LNB.

Well, if a second tuner comes on, then more power flows to the lnb, not less. Of course if you turn off the second tuner then
there could be an effect.

The 22kHz issue suggested by rolfw is another possible reason, but then it should be dependent on whether you tune high or low frequencies.

The last LNB I installed was an inverto quad and was fine.
ALPS quad was bad.

 

[schussel]

OK thank you guys. I understand nothing much I can do in terms of wiring/config etc - but only purchase other hardware and experiment. Still a bit disappointing, that the LNB seems had been tested "very good" by some respective media [this make] - but we all know parts suppliers may change any time.

22kHz seems possible - as the issue does not occur always. Most importantly, I never ran into an issue with recordings *.ts on my PC so for now it's more a nuisance than a real pain.

rolfw's Quad LNB suggestion is interesting - as I had decided against a quad, as I only need 2 and assumed a quad might tend to deliver lower quality output than a twin LNB.

 

[rolfw]

OK thank you guys. I understand nothing much I can do in terms of wiring/config etc - but only purchase other hardware and experiment. Still a bit disappointing, that the LNB seems had been tested "very good" by some respective media [this make] - but we all know parts suppliers may change any time.

22kHz seems possible - as the issue does not occur always. Most importantly, I never ran into an issue with recordings *.ts on my PC so for now it's more a nuisance than a real pain.

rolfw's Quad LNB suggestion is interesting - as I had decided against a quad, as I only need 2 and assumed a quad might tend to deliver lower quality output than a twin LNB.

There is no perceivable difference in performance betwee single, twin and quad LNBs on medium strength signals in my experience.

 

[deeptho]

OK thank you guys. I understand nothing much I can do in terms of wiring/config etc - but only purchase other hardware and experiment. Still a bit disappointing, that the LNB seems had been tested "very good" by some respective media [this make] - but we all know parts suppliers may change any time.

I asked a question about that in one of the other threads: it is of course nice to have a sensitive lnb, but nobody seems to consider other aspects such as switching properly without cross port interference and lasting for a long time (both the electronics and the plastic of the casing)

22kHz seems possible - as the issue does not occur always. Most importantly, I never ran into an issue with recordings *.ts on my PC so for now it's more a nuisance than a real pain.

rolfw's Quad LNB suggestion is interesting - as I had decided against a quad, as I only need 2 and assumed a quad might tend to deliver lower quality output than a twin LNB.

I always buy quads. Whether or not there is less interference between physically nearby ports, I do not know. I imagine it is really
due to the design of the lnb and not specifically to which port is where on the lnb.

PS. Another way to prevent cross-port interference is to keep the cables powered on all the time. tvheadend allows this option, but a TV
may not offer it.