Poor quality on STB improved by DVB PCI ??????

[chc59]

This issue involves the signal quality of c-band freqs on a SV8000HD and how it is affected positively by another tuner on the same freq. Before I start fumbling into troubleshooting this problem, I thought I might run it by you folks for any suggestions on where to look first. Best description of the problem would be I have tuned to a c-band HD freq on the Sonicview. The signal is marginal, barely at the threshold, with lots of stuttering. I then tune to the same freq on the dvb pci card in the pc. DVB card shows a strong signal. The signal on the Sonicview goes up dramatically. Turn off the card and the Sonicview goes back to nfg. I have noticed that it only seems to apply to HD signals. For instance, there is a c-band sat that has both the SD and the HD freqs for the same programming. The SD freq comes in at 100% on the SV but the HD freq is marginal, that is until I fire up the dvb card as well. My setup is a network of multiswitches and diseqc switches feeding several receivers. On c and ku band, the antenna position and polarity are controlled by a 4DTV. To feed the dvb receivers, the c lnb comes into one input of a multiswitch and ku comes into the other input. Outputs from that multiswitch feed diseqc switches for the individual dvb receivers.

Appreciate any insights that you might have. I do not understand what is going on here. It would seem that the switches and cabling are ok. I wonder about the SV and its abilities on FTA HD. Not a big deal for me, just a PITA.

Joe

 

[Smith P.]

Check voltage at LNB side after both variants.

 

[Anole]

Yes, I agree with Smith
There's a chance you might have a low voltage problem to the LNBs through your switches.
Look to see if the common thing is Vertical or Horizontal polarity, not SD vs HD.

Also, if any of your multiswitches can be powered, try doing that.

It's always possible that you have powered LNBs on both sides of some switch, and it leaks the OFF signal through to your receiver.

If you could provide a map of how they are all wired up, maybe we could help.

 

[chc59]

P,

Thanks for replying. But, you lost me there. Trying to think this through, in the 4DTV and DVB receiver setup, the voltage to the big dish lnb's is coming from the 4DTV and dc blocked on the DVB receiver side. The DVB's (3) then only control the multiswitch and their respective diseqc's. All c-band stuff comes into all dvb's via one input of the multiswitch (with ku on the other switch input). All c-band stuff, regardless of polarity, is entered into the DVB's as Vertical. All BUD ku is entered as Horizontal. That is how I select the BUD's c or ku at the multiswitch. Actual polarity is controlled by the 4DTV. If the c-band freq for the SD signal is at 100% quality on the Sonicview with no help from the pci card, would not the SV's control output be ok? If the multiswitch needed help from, say the pci card, would it not need help on both SD and HD freqs? "Is a puzzlement"

Anatole,
Thought provoking. Leakage. Himmm. Reflecting on the above, the DVB's do not send voltage to the big dish lnb's and do not control polarity. That is done by the 4DTV. The way I have it set up, all c-band freqs are loaded into the dvb's at the same polarity. So, not a polarity issue. On the sample sat, yes, the SD and the HD are at different polarities but not as far as the dvb receivers are concerned. Just different frequencies.

Joe

 

[chc59]

Here is a simple schematic.

Joe

 

[Smith P.]

I would measure the voltage and will add results to your picture. It would eliminate wide guesses.

 

[Hermitman]

I'll throw a couple of pennies in. It may not be polarity but polarity voltage flow. On the Sonicview, check the 22khz configuration for the HD channels. Have you checked that all switch and antenna settings are exactly the same for both the Sonicview and the card? I'm assuming the splitters internally have the DC block. Make sure the flow arrows are pointing the proper direction. There are different types of splitters with different voltage flow patterns. Since the common point is the 3x4 switch, you might try and bypass the switch with a F-F connector to see what happens. Good luck.