questions about TBS6902 (1 Viewer)

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two4two

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Jul 4, 2006
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It says it has two tuners. The card appears to have two connectors. Are they BOTH for LNB in? So one could be a KU LNB and the other a C LNB? Does this card provide power to the LNB? And if I have two LNBs input, one to each connector, does it power BOTH LNBs? Is there a LINUX driver? I would use my DSR-922 to position the dish and power the polarizer, but I would not connect any LNB to the DSR-922. Is this OK to do this? I'm thinking that the DSR-922 would select the correct polarizer setting based on TP selected on the DSR-922 even though it would not actually be connected to the TP. I will use the TBS-6902 display on my PC to visualize signal strength while using the dish positioner and polarizer control on the DSR-922 to fine-tune. Thanks all.
 

Titanium

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Yes to all of your questions. :D

One tuner could be connected to both C and KU with a DiSEqC switch. This would leave the second tuner for other uses like being set-up on other dishes for DVR/streaming, etc.

The LNBs do not need to pass through the DSR-922, but in the configuration that you mention, I would. Let the DSR-922 provide the power and take some strain off the card. :)

I use the TBS6983 daily with a ASC1 for automatic positioning and polarity servo control. Much easier not to coordinate a manual controller to synchronize the satellite selection and the polarity position for each service change. This also enables automatic H/V spectrum scans, x-pol comparison, unattended scanning and recording.
 

johnnynobody

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It'll work with Linux but as far as I'm able to determine you'll have to write your own script or app to make it blind scan.
 

two4two

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Jul 4, 2006
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Yes to all of your questions. :D

One tuner could be connected to both C and KU with a DiSEqC switch. This would leave the second tuner for other uses like being set-up on other dishes for DVR/streaming, etc.

The LNBs do not need to pass through the DSR-922, but in the configuration that you mention, I would. Let the DSR-922 provide the power and take some strain off the card. :)

With the DiSEqC switch I would then use my Kaffeine app and change tuner, right? Does a DiDEqC switch send power thru all ports so that both my LNBs will get power?

I've tried the configuration you mention with the splitters before. I original did it with an FTA set-top box and it worked great with me being able to view FTA analog and clear Digicipher on C-band thru the DSR-922 and all the DVB thru the STB. When I moved to a TBS-6925 it didn't work. In fact, the 6925 got fried. So I returned it and the replacement got fried. I could not figure out why they got fried because I used the very same setup as with the STB: splitters with DC block and DiSEqC switch on the 6925 side while LNB power came from the DSR-922. Since I could never figure out why the TBS-6925s got fried I thought I'd give up the clear analog and clear Digicipher in favor of not frying the TBS-6902.
 

two4two

Thread Starter
SatelliteGuys Family
Jul 4, 2006
48
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It'll work with Linux but as far as I'm able to determine you'll have to write your own script or app to make it blind scan.
Doesn't Kaffeine scan? Except I have to code in all the TPs. There is a scan app from one of the users but I never installed it because I'd need to build his kernel and that failed for me.
 

johnnynobody

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Doesn't Kaffeine scan? Except I have to code in all the TPs. There is a scan app from one of the users but I never installed it because I'd need to build his kernel and that failed for me.

Yes it does but it isn't blindscan. It'll only scan transponders that are listed in scanfile.dvb. That file can be edited to manually add more transponders.

I tried updatelee's project on Ubuntu but couldn't get it to work either. Some people have mentioned that his stuff works on Debian 8 but I couldn't get it to work there either.
 

Titanium

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A DiSEqC switch normally only sends power to the selected port. This is usually desirable, rather than powering all connected LNBs and stressing the power supply. Note: If you are attempting to power LNBs with a FTA receiver, PCI or USB tuner, the LNB voltage must be set to 18V (horizontal) at all times to provide proper voltage for the LNB requirements and performance.

I would look for transient or balancing voltages traveling between the computer and the satellite system components. The computer power supply is grounded via the NEMA 5-15p power plug. The DSR-922 and the dish should be connected/bonded to the same structure ground. STBs typically use SMPS (switched mode) and float the ground with no connection to structure ground.

Any voltage seeking ground, or a voltage potential traveling between multiple unbonded grounding points might find a path through the grounded computer and toast the weakest link in the PCI card. A typical STB provides no path to ground, so is not damaged. BTW... this is why so many AV forums have threads about failed HDMI ports on STBs and monitors. HDMI ports are very weak point (expensive fuse) that is easily damaged by stray voltages.

I am, sure that what ever killed two 6983 cards will also kill the 6902! :eeek
 
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two4two

Thread Starter
SatelliteGuys Family
Jul 4, 2006
48
1
A DiSEqC switch normally only sends power to the selected port. This is usually desirable, rather than powering all connected LNBs and stressing the power supply. Note: If you are attempting to power LNBs with a FTA receiver, PCI or USB tuner, the LNB voltage must be set to 18V (horizontal) at all times to provide proper voltage for the LNB requirements and performance.

I would look for transient or balancing voltages traveling between the computer and the satellite system components. The computer power supply is grounded via the NEMA 5-15p power plug. The DSR-922 and the dish should be connected/bonded to the same structure ground. STBs typically use SMPS (switched mode) and float the ground with no connection to structure ground.

Any voltage seeking ground, or a voltage potential traveling between multiple unbonded grounding points might find a path through the grounded computer and toast the weakest link in the PCI card. A typical STB provides no path to ground, so is not damaged. BTW... this is why so many AV forums have threads about failed HDMI ports on STBs and monitors. HDMI ports are very weak point (expensive fuse) that is easily damaged by stray voltages.

I am, sure that what ever killed two 6983 cards will also kill the 6902! :eeek


Thank you Titanium. Now, a question. How can a computer -- (since computer power supplies have 12V) -- supply 18V to an LNB?
 

johnnynobody

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I haven't looked at a schematic (if there is one) but my guess is that they use a voltage tripler (3x12=36) then divide it in half (36/2=18) with a voltage divider circuit. But, I'm just guessing.
 

ancient

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May 12, 2014
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A DiSEqC switch normally only sends power to the selected port. This is usually desirable, rather than powering all connected LNBs and stressing the power supply. Note: If you are attempting to power LNBs with a FTA receiver, PCI or USB tuner, the LNB voltage must be set to 18V (horizontal) at all times to provide proper voltage for the LNB requirements and performance.

Without addressing the rest of your post, either I am totally misinterpreting what you are saying here or your experience and mine have been totally different. I use TBS cards in my TVHeadEnd backend system and I also have 4-port DiSEqC switches in use, connected to various ports on the tuner cards. All my LNB's, both C and Ku band, are voltage-switched. I have NO problem receiving both vertical and horizontal transponders, and I certainly do not try to force any voltages to 18V, which would entirely defeat the purpose of having a voltge-switched LNB.

So either you're addressing a special situation and I'm not following the thread, or you've had some bad experiences trying to use LNB's on the low voltage setting that I have not experienced. If it's the latter then my guess would be that whatever computer you were using wasn't supplying enough current to the tuner cards. Or, maybe you were using a different brand of DiSEqC switch that wasn't passing enough power to the LNB's. I do remember that when starting this project many months ago I wound up having to buy new DiSEqC switches because the ones that I had been using, that worked fine with my old digital receiver, did not work very well with the TBS tuner cards, though I don't recall what the specific problems were anymore.

I apologize in advance if you and I are talking about something totally different, but from that post it appeared you were saying that voltage switching would not pass through the DiSEqC switches to the LNB's and I can tell you that it's never been a problem with my setup, at least not since replacing the DiSEqC switches, and I don't think I had that particular issue even with the old DiSEqC's, though it's been so long that unfortunately I don't recall exactly what caused me to replace them.
 

Titanium

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You have misunderstood. In the original post by two4two, he indicates that the set-up is using a C and KU type feedhorn with servo polarity control. These LNBs are fixed polarity and spec'd to operate on 15-24Vdc. In this case, the LNBs will provide optimized performance when provided 18Vdc (some models will not operate if powered with 13Vdc).
 

ancient

SatelliteGuys Pro
May 12, 2014
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You have misunderstood. In the original post by two4two, he indicates that the set-up is using a C and KU type feedhorn with servo polarity control. These LNBs are fixed polarity and spec'd to operate on 15-24Vdc. In this case, the LNBs will provide optimized performance when provided 18Vdc (some models will not operate if powered with 13Vdc).

Thank you for clearing that up. I was really hoping I was interpreting that wrong. Now that I understand it's the ones that use servo motors for polarity control, I can see that some of them might not work well, or at all, with only 13 volts. I don't use any of those anymore, I only use the polarity switched kind, and also separate dishes for C and Ku bands, so I wasn't even thinking about that type of LNB. Again, my apologies for the misinterpretation.
 
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